Product Guides
Cutting Tool Materials Guide: HSS, Cobalt, Carbide, PCBN & PCD Explained
Master cutting tool material reference — seven tool material families documented with hardness, thermal stability, toughness and cost positioning. When HSS is enough, when carbide pays back, when PCBN or PCD become economical.
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HSS vs. Carbide: Quick Reference Guide
Choosing between High-Speed Steel (HSS) and carbide tools depends on your machining needs, materials, and production requirements. Here’s a breakdown to help you decide. Quick Comparison: HSS vs. Carbide Feature HSS (High-Speed Steel) Carbide Durability Tougher, resists chipping, good for varied applications Harder but more brittle, best for stable setups Speed Suitable for lower-speed operations Designed for high-speed machining Lifespan Wears faster but can be resharpened Lasts longer without losing sharpness Cost More affordable, great for small production runs Higher upfront cost, better for large-scale jobs Best Use General-purpose drilling, tapping, and milling High-precision and high-volume machining Choosing the Right Tool: Key Factors 1. Work Volume & Cost ✓ High production & hard materials? Carbide lasts longer and performs better at high speeds.✓ Occasional machining? HSS is more affordable and can be resharpened. Popular HSS Tools Popular Carbide Tools HSS Jobber Drill Bits Carbide Rotary Burrs HSS Step Drills Carbide Tipped Annular Cutters 2. Material Hardness ✓ HSS: Best for mild steel, aluminum, and softer alloys.✓ Carbide: Ideal for stainless steel, cast iron, and hardened materials. Best Tools for Mild Steel & Aluminum: Best Tools for Stainless Steel & Harder Materials HSS Hole Saws Carbide End Mills HSS Taps & Dies Tungsten Carbide Lathe Inserts 3. Speed vs. Tool Life ✓ Carbide: Runs at higher speeds, stays sharper longer.✓ HSS: Wears faster but can be resharpened to extend its life. High-Speed Cutting Tools Tools for Longer Lifespan Carbide Hole Saws Solid Carbide Drill Bits 4. Machine Setup & Rigidity ✓ Less stable setup? HSS is more forgiving and resists chipping.✓ High-precision, rigid machines? Use carbide to avoid breakage. Rigid & Precision Machining Tools Carbide Micro Drills Carbide Countersinks 5. Surface Finish & Precision ✓ HSS: Good for general machining but may require secondary finishing.✓ Carbide: Provides a smoother finish and holds tighter tolerances. Smooth & Precise Cutting Tools Carbide-Tipped Router Bits Carbide Slitting Saws 6. Cooling & Lubrication ✓ HSS: Needs cutting fluids to reduce wear.✓ Carbide: Can be used dry, but lubrication improves lifespan. Coolants & Lubrication Supplies Cutting Fluids & Coolants Coolant Hoses & Systems 7. Application-Specific Advice Application Best Choice Recommended Tools Drilling HSS for general use, carbide for high-speed drilling HSS Jobber DrillsCarbide Annular Cutters Milling Carbide for precision & speed, HSS for low-speed operations HSS End MillsCarbide Router Bits Tapping HSS for most tasks, carbide for production & hard materials HSS Taps & DiesCarbide Threading Inserts Other Tips: If speed, precision, and durability are your top priorities, invest in carbide tools. If you need an affordable, flexible option that can be resharpened, HSS is the way to go. Shop All Machining Tools: Browse our full range here People Also Ask — HSS vs. Carbide: Quick Reference Guide Q: When should I use carbide tooling instead of HSS? Choose carbide when cutting hardened materials (above 45 HRC), high-speed production where tool changes are costly, abrasive materials (cast iron, fibreglass), or when surface finish requirements are tight. HSS remains the better choice for interrupted cuts on a manual lathe, low-volume workshop work, and materials that are prone to carbide chipping — such as some titanium alloys and work-hardened stainless steel. Q: Why do carbide drill bits break so easily? Carbide is extremely hard but brittle — it fails suddenly under shock loading or lateral force rather than bending as HSS does. Common causes of carbide breakage: drilling without centre-drilling first (the bit deflects on entry), insufficient rigidity in the setup, drilling too slowly (generates heat), using hand-feed on manual machines (uncontrolled infeed), or selecting carbide for interrupted or cross-hole drilling where HSS is more appropriate. Q: Are Sutton Tools drill bits made in Australia? Yes — Sutton Tools manufactures its HSS and HSS-Co (cobalt) drill bits in Melbourne, Victoria, making them one of Australia's few remaining domestic cutting tool manufacturers. Sutton's M35 (5% cobalt) and M42 (8% cobalt) drills are well-regarded for stainless steel, Inconel, and other difficult-to-machine materials. Australian-made tooling also simplifies supply chain for businesses with local content requirements. Q: Can HSS tooling be resharpened? Yes — HSS drills, end mills, and lathe tools can be resharpened repeatedly by an experienced tool grinder, extending their useful life significantly. Carbide can also be reground, but requires diamond wheels and is typically only economical for larger tooling. For high-volume workshops, a tool grinding service contract is often more cost-effective than replacing worn HSS tooling outright.
Read moreEnd Mill Guide: Geometry, Coatings & Selection
End mills are the workhorses of milling — whether you're running a CNC machining centre, a manual knee mill, or a benchtop hobby CNC. They cut on the side and the end, take material away in three dimensions, and live or die on getting the right combination of geometry, material, coating, flute count, and feed and speed for the job. Get the choice right and an end mill will make hundreds of parts. Get it wrong — most often the wrong coating for the work material, or the wrong flute count for the depth of cut — and you'll burn through tools, get poor surface finish, or pull the cutter in two. This guide walks through every variable that matters: types and geometry, HSS vs cobalt vs carbide, coatings (and the AlTiN-on-aluminium trap that catches plenty of beginners), flute count rules, helix angle, climb vs conventional milling, speeds and feeds, applications, failure modes, and a practical starter set for an Australian workshop. AIMS stocks 50+ end mills across square, ball nose, corner radius, corner chamfer and milling cutter ranges — Sutton (made in Australia), Bordo, and premium imports. Browse our End Mills collection for what's in stock, or read on for how to choose. Bookmark our Engineering Reference Charts hub for related sizing tables, conversion charts and Australian standard references across 9 topic clusters. End Mill Selector — Choose by Operation This guide is a working selector tool — not just a reference. Use it to choose the right end mill for your operation. Pick your scenario below for a direct path to the right tool family, or scroll down for the full geometry / material / coating analysis. How to use: 1. Pick your operation 2. View the range 3. Choose diameter, flute count and material from the collection General Slotting / Profiling Universal — most common shape Square View range → 3D Contours / Mould Work Spherical tip — smooth surface Ball Nose View range → Stronger Corners Reinforced corner — less chipping Corner Radius View range → Chamfering / Edge Break Angled tip — 45°, 60° etc. Corner Chamfer View range → Production Carbide VHM 3xD or 5xD — long life Solid Carbide View range → Workshop HSS Cheaper, easier to regrind HSS / HSS-Co View range → Indexable / Insertable Replaceable carbide inserts Indexable View range → Roughing / High MRR Corn-cob teeth — fast stock removal Roughing View range → Sutton dominates the AIMS end mill range — Black Magic carbide (Helica coating), Premium VHM, HSS roughing and finishing series. Bordo for HSS general-purpose. Need help selecting? Call us on (02) 9773 0122. Jump to: Geometry Material Flutes Helix Angle Coatings Milling Direction Starter Set Related Selectors AIMS Top Picks — Pick the Right End Mill Fast Sutton's E-series end mill range is AIMS's depth pick — solid carbide VHM (Vollhartmetall), cobalt HSS, and specialty coatings (TiAlN, AlCrN, Helica, Alnova). Recommendations below by material × job. Open the linked product to choose diameter (3mm–25mm) and flute count. Call (02) 9773 0122 for sizing help. For Mild Steel (Workshop Default) Job Geometry AIMS recommendation Why this one General slotting + contour 2-flute slot drill, HSS-Co Sutton E100 8% Cobalt Slot Drill Workshop HSS-Co default — cheaper than carbide, forgiving on manual machines. 8% cobalt for steel work Production slotting + contour 2-flute slot drill, VHM Sutton E600 2-Flute VHM Slot Drill Solid carbide (VHM) — 4-5× tool life of HSS-Co at higher cutting speeds. Production CNC default Side milling + profile (4-flute) 4-flute VHM TiAlN Sutton E604 4-Flute VHM TiAlN 4-flute for better finish + tool life on profile work. TiAlN coating for steel cutting heat resistance 2-flute end mill (not slot drill) 2-flute VHM TiAlN Sutton E603 2-Flute VHM TiAlN 2-flute end mill with TiAlN — better than slot drill for chip clearance in deeper pockets Heavy roughing (high MRR) Roughing 8% Cobalt Sutton E146 Roughing Endmill 8% Cobalt Knuckle-tooth roughing geometry — fastest stock removal on mild steel before finishing pass For Stainless Steel & Hardened Steel Job Geometry AIMS recommendation Why this one Stainless workshop (general) 4-flute VHM TiAlN Sutton E604 4-Flute VHM TiAlN TiAlN coating for stainless heat resistance — workshop standard for 304/316 work Hardened steel (>30 HRC) 4-flute VHM AlCrN Sutton E535 VHM Ultra AlCrN Long AlCrN coating for >800°C heat resistance — for hardened tool steel + heat-treated parts Hardened steel short reach 4-flute VHM AlCrN short Sutton E533 VHM Ultra AlCrN Short Short version of E535 — rigidity for tighter tolerance on hardened steel Premium tool steel work Helica VHM Sutton E459 VHM Helica Helica coating — premium for tool steel, mould steel, P20 plate work For Aluminium & Non-Ferrous Job Geometry AIMS recommendation Why this one Aluminium chip-clearing (1-flute) 1-flute VHM Ultra short Sutton E444 1-Flute VHM Ultra Single flute for aggressive chip evacuation in aluminium. The "won't gum up" choice 3-flute aluminium production 3-flute Harmony Sutton E480 3-Flute Carbide Harmony Pferd Harmony 3-flute — balanced chip clearance + finish for production aluminium For Ball Nose (3D Contouring) Job Geometry AIMS recommendation Why this one 3D contour workshop default 4-flute VHM ball nose Sutton E606 4-Flute Ball Nose VHM 4-flute ball nose — workshop default for 3D mould + contour work Steel 3D contour (coated) 4-flute VHM TiAlN ball nose Sutton E607 4-Flute Ball Nose TiAlN TiAlN-coated ball nose for harder steel contour work Slotting 3D form (ball nose) 2-flute ball nose slot drill Sutton E605 2-Flute Ball Nose TiAlN Ball nose slot drill — for full-width 3D plunging + ramping Deep pocket 3D contour 4-flute ball nose extra long Sutton E320 Ball Nose Extra Long Extra-long reach for deep mould + die work For Corner Radius & Chamfer (Tool Life Booster) Job Geometry AIMS recommendation Why this one Corner radius (general) 4-flute corner radius VHM Sutton E462 R0.3 VHM Helica Long R0.3 corner radius — eliminates corner stress concentration. 5× tool life vs square corner Premium corner radius (AlCrN) 4-flute corner radius VHM AlCrN Sutton E559 Corner Radius VHM Ultra AlCrN AlCrN + corner radius — for hardened steel mould + die work 5-flute premium 5-flute Alnova HA Sutton E466 5-Flute Alnova HA 5-flute = better finish + tool life on production work. Alnova premium coating Chamfer end mill (corner radius combo) 4-flute chamfer + corner radius Sutton E458 Chamfer + Corner Radius VHM TiAlN Combo geometry — chamfer edge + corner radius in one tool. Saves a setup Buying tip from AIMS: Sutton's Australian-made VHM (solid carbide) range is the workshop standard for AU machining. Match coating to material: TiAlN for general steel, AlCrN for hardened + heat-stable, Helica for premium tool steel, Alnova for high-end. For aluminium, never use TiAlN (chemical reaction causes premature wear) — use uncoated VHM or specific aluminium coatings. 4-flute = better finish, 2-flute = better chip clearance for slotting, 1-flute = maximum chip clearance for aluminium.What is an end mill? An end mill is a rotary cutting tool designed for milling — removing material from a workpiece by feeding it sideways past a rotating cutter. Unlike a drill bit (which only cuts on its tip and is designed to plunge straight down), an end mill cuts on both its end and its sides, allowing it to take side cuts, profile shapes, slot, ramp, and machine in three dimensions. The basic anatomy is straightforward: a cylindrical shank that grips into a tool holder (collet, Weldon, hydraulic, shrink-fit, or integral taper); a cutting flute section with helical grooves that form the cutting edges; and an end geometry that may be flat (square), spherical (ball nose), or have a small corner radius (bull nose). Modern end mills are mostly made from solid carbide for production work, with HSS and cobalt still common for manual milling, light-duty CNC, and budget tooling. End mills differ from drill bits in three important ways: they cut on the periphery as well as the end (so they can side-mill); their flutes are designed for chip evacuation in a sideways cut rather than down a vertical hole; and they are generally not designed for plunge drilling — only end mills with a centre-cutting design (true centre-cutting flutes that meet at the centreline) can plunge straight down without a pre-drilled pilot. We cover this distinction in the applications section below. End mill types by geometry End mills come in many geometries, each suited to specific operations. Type Geometry Best for Square (flat) end Flat-bottomed, 90° corners General-purpose milling, slotting, profiling, pocketing with sharp internal corners. The default workhorse. Ball nose Hemispherical end, full radius 3D contouring, mould and die work, finishing curved surfaces. Always leaves a small scallop — needs fine stepover for surface finish. Corner radius (bull nose) Flat end with small corner radius General-purpose where corner strength matters more than sharp internal corners. Reduces stress concentration at the corner — much longer tool life than square end on hard materials. Corner chamfer Flat end with 45° (or other) chamfer at corner Combined milling and edge-breaking — chamfer the part edge in the same operation as the profile cut. Roughing (corn-cob) Serrated cutting edges along the length Heavy stock removal — breaks chips into small pieces, evacuates them efficiently. Surface finish is rough; follow with a finishing pass. Tapered Conical body — narrows toward tip Mould and die work with draft angles, tapered slots, EDM electrode roughing. T-slot cutter Wide flat cutter on a narrow shank Cutting T-slots and undercuts — used to machine machine-tool-table T-slots, jig fixtures, dovetail relief. Dovetail Angled cutting edges (45°, 60° common) Cutting dovetail slots in fixtures, slides, and machine ways. Thread mill Thread-form cutting edges Milling internal or external threads — useful for large threads, blind holes, and material that work-hardens (where a tap would seize). Drill mill Square end + drill point Combination tool — drills a hole then mills the side. Used in single-tool jobs to reduce tool changes. Engraving / V-bit Conical V-shape with sharp tip Engraving, fine detail, sign work. Cuts with the side of the V — tip angle determines line width. AIMS stocks the most common types as dedicated collections — Square End Mills, Ball Nose End Mills, Corner Radius End Mills, and Corner Chamfer End Mills. For tapered, T-slot, dovetail, and thread mills, contact us — we can source most specialist geometries through our supplier network. Material substrate: HSS vs cobalt vs carbide The cutting tool material — the substrate — is the most fundamental choice. It determines how fast you can run the tool, how long it will last, and what work materials you can cut. Substrate Hardness / Heat resistance Best for Trade-off High-Speed Steel (HSS) ~63–66 HRC, to ~600°C Hand mills, manual machining, soft materials (aluminium, brass, plastic, mild steel at low speed). Forgiving — can be reground. Slowest cutting speed. Wears quickly on harder materials. Cobalt HSS (M35, M42) ~67–70 HRC, to ~700°C HSS-grade work but at higher speeds, or harder materials like stainless steel. Stronger and more heat-resistant than plain HSS. More expensive than HSS; still well below carbide in pure cutting speed. Solid carbide (tungsten carbide) ~89–93 HRA, to ~900°C+ Production CNC, all metals including hardened steel, stainless, titanium. The default for serious machining. Brittle — chips and shatters under shock or interrupted cuts; cannot be reground at home; more expensive than HSS. Cermet / ceramic To 1,200°C+ High-speed finishing of cast iron and hardened steel. Specialist applications. Even more brittle than carbide. Requires very rigid setup and high-speed spindles. CBN / PCD Hardest available Polycrystalline diamond (PCD) for non-ferrous and composites; cubic boron nitride (CBN) for hardened steel. Specialist tooling, premium price. Not for general use. The practical rule: Use carbide for any production CNC work and any material above mild steel. Use HSS or cobalt for manual milling, hobby CNC, deep slotting where carbide breakage is a risk, or budget situations. AIMS stocks both — Sutton and Bordo HSS / cobalt, plus Sutton VHM solid carbide and various premium imports. For the full HSS vs carbide upgrade decision — RPM thresholds, cost-per-cut analysis, when each substrate wins, and the cobalt HSS bridge-upgrade — see our Carbide vs HSS End Mill: When to Upgrade deep-dive. Solid carbide vs indexable / insertable end mills Carbide end mills come in two construction styles: Solid carbide — the entire cutter (shank and flutes) is one piece of tungsten carbide. Best for small-to-medium diameters (typically up to 20–25 mm) and where dimensional accuracy matters most. When the cutting edges wear out, the whole tool is replaced or regrind. Indexable / insertable — a steel body with replaceable carbide inserts clamped or screwed in. Best for larger diameters (typically 16 mm and up) and high-volume work. When inserts wear, you rotate to a fresh cutting edge or replace just the insert — the body is reusable across many insert sets. The cost-per-edge analysis: A 16 mm solid carbide end mill might cost $80 and have 4 cutting edges total before scrap. An insert-type tool body costs more upfront ($200+) but each insert provides 2–4 fresh corners, and a single insert refill at $30–50 gives you another full set of edges. Over a long production run, indexable wins on cost per cubic centimetre of material removed. For lower volumes or one-off work, solid carbide is cheaper and simpler. Indexable end mills also let you mix insert grades for different work — a tougher grade for roughing, a finer grade for finishing — without changing tool bodies. Practical Machinist threads on indexable selection consistently note this flexibility advantage. Flute count: what 2, 3, 4, 5, 6 and 7+ flutes do The number of flutes is one of the most-asked questions and one of the most misunderstood. There is no single best answer — flute count is a trade-off between chip evacuation, cutting-edge engagement, and rigidity. Flute count Best for Why 1 (single flute) Plastic, very soft aluminium, hobby CNC routers Maximum chip clearance — handles long stringy chips that would weld to a multi-flute cutter. 2 flute Aluminium, brass, slotting, plunging, hobby work Big flute valleys = excellent chip evacuation. Plunge-capable (centre-cutting). Lower productivity than 3-flute on aluminium. 3 flute Aluminium and other non-ferrous (the modern preferred choice) Best balance of chip room and feed rate on aluminium. Most premium aluminium-specific end mills are 3-flute. 4 flute Steel, stainless, cast iron — general workshop default Smoother cut, better surface finish, higher productivity than 2-flute on ferrous metals. Smaller chip valleys, so not for aluminium where chips clog. 5, 6, 7 flute High-speed finishing in steel and stainless, light radial engagement More cutting edges = higher feed per minute at the same chip load. Only works at low radial engagement (under ~20% of cutter diameter) where chip clearance isn't the bottleneck. 8+ flute Specialist finishing, hard milling Maximum number of edges in contact for ultra-fine finishes. Niche applications. The aluminium rule (forum-validated, Practical Machinist + r/Machinists consensus): use 2 or 3 flute on aluminium. Aluminium chips are large and gummy; the deeper flutes of a 2- or 3-flute cutter let chips evacuate cleanly. A 4-flute end mill in aluminium will pack the flutes with chips, causing the chip to weld back to the cutter and either burn the cutter or break it. The depth-of-cut rule (from r/Machinists): up to about 2–3× cutter diameter depth, a 4-flute is fine in steel. Beyond 3× diameter — proper deep slotting — step up to 5, 6, or 7 flutes only if radial engagement is light (high-feed/peeling style). At full radial engagement (slotting), more flutes hurt because the chips have nowhere to go. Odd flute count for chatter control: 3, 5, and 7-flute end mills break up the regular tooth-impact harmonic that causes resonant chatter. On long-reach work, thin-wall parts, or harmonics-prone setups, switching from a 4-flute to a 5-flute (or from a 6-flute to a 5- or 7-flute) often dramatically reduces chatter without changing anything else. Helix angle and variable helix The helix angle — the angle of the cutting flutes relative to the tool axis — controls the smoothness of cut, the axial forces on the spindle, and chatter behaviour. Low helix (15–30°) — strongest tooth, lowest axial pull, used for hard materials and roughing. Less smooth cutting, more vibration. Standard helix (30°) — workhorse general-purpose angle. Good balance. High helix (38–45°) — smooth shearing cut, excellent finish, lower cutting forces. The default for aluminium and finishing in steel. Pulls the tool axially up into the spindle — needs solid pull-in on the tool holder. Variable helix (mixed angles) — different helix angles on different flutes (e.g. 35°/37°/35°/37°). Breaks up tooth-pass harmonics for chatter resistance. Almost always paired with unequal flute spacing for the same reason. Standard on premium stainless and titanium end mills. Variable helix + unequal flute spacing is the modern stainless steel and titanium recipe — the irregular tooth strikes prevent the chatter resonance that work-hardens stainless and tears titanium. Sutton, Iscar, Sandvik and most premium brands offer this configuration. Coatings: TiN, TiCN, TiAlN, AlTiN, ZrN, DLC, diamond Coatings extend tool life by reducing friction, raising the temperature limit before the carbide softens, and acting as a chemical barrier between the cutting edge and the work material. The wrong coating, however, can be worse than no coating at all — particularly with aluminium. Coating Colour Max temp Best for Avoid for Uncoated (bright carbide) Silver/grey ~600°C Aluminium, copper, brass, plastic — non-ferrous where coating affinity is a problem Steel and stainless above light cuts TiN (Titanium Nitride) Gold ~600°C General-purpose for HSS in mild steel and cast iron. Cheap, gives modest life increase. Demanding applications TiCN (Titanium Carbo-Nitride) Blue-grey to violet ~400°C Cooler-running operations, abrasive materials, cast iron at moderate speed High-temperature work TiAlN (Titanium Aluminium Nitride) Violet-bronze to dark grey ~800°C Steel, stainless, cast iron, hardened materials. Forms a protective Al₂O₃ layer at high temp. Aluminium — coating contains Al and chips weld to the tool AlTiN (Aluminium Titanium Nitride) Dark grey/black ~900°C High-temp steel, stainless, hard materials. Higher Al than TiAlN — even more heat-resistant. Aluminium — strong galvanic affinity, severe chip welding ZrN (Zirconium Nitride) Light gold/silver ~600°C Aluminium, copper, brass — low affinity to non-ferrous. The traditional aluminium coating. Steel and stainless AlCrN (Aluminium Chromium Nitride) Blue-grey ~1,100°C Hardened steel, titanium, dry/MQL machining, very high-temperature work Soft non-ferrous DLC (Diamond-Like Carbon) Black, smooth ~400°C Aluminium (premium), copper, graphite, plastics, fibreglass — extremely low friction surface Hot work — DLC degrades above 400°C CVD Diamond Matte grey-black ~700°C Graphite, carbon-fibre composites, ceramics, MMC. Ultra-hard. Steel and any iron-bearing material — diamond reacts with iron at cutting temperatures and degrades rapidly Warning: Never use TiAlN or AlTiN coated end mills on aluminium. TiAlN and AlTiN coatings contain aluminium oxide. When cutting aluminium, the aluminium chips have strong chemical and mechanical affinity for the aluminium-bearing coating — chips weld to the cutting edge ("built-up edge"), the welded chip then breaks off taking carbide with it, and the cutter fails rapidly. Forum consensus across Practical Machinist and r/Machinists is unanimous on this point. For aluminium, use uncoated bright carbide, ZrN, or DLC. AIMS stocks aluminium-specific Sutton and premium imports — call us if you need a specific spec. Coating selection by work material Work material Recommended coating Why Aluminium and aluminium alloys Uncoated, ZrN, or DLC Avoid Al-bearing coatings (TiAlN, AlTiN). Polished/uncoated carbide cuts cleanly. ZrN reduces built-up edge. DLC for premium production. Mild and medium steel TiAlN or AlTiN Heat resistance prevents tool softening. Bronze-violet TiAlN is the production default. Stainless steel (304, 316, 17-4) TiAlN or AlTiN with variable helix and unequal flute spacing Stainless work-hardens under chatter. Variable geometry breaks the harmonic; coating handles the heat. Hardened steel (42–55 HRC) AlTiN or AlCrN High-temp coatings handle the heat of hard milling. Many AlCrN-coated end mills are rated to 65 HRC at speed. Cast iron TiAlN or TiCN Abrasive material — coating provides wear barrier. TiCN for grey iron at moderate speed; TiAlN for nodular iron at higher speed. Titanium and Ti alloys (Ti6Al4V) AlCrN or specialist Ti coatings; some prefer uncoated polished Ti has low thermal conductivity — heat stays in the cutter. Specialty coatings handle this; some shops still prefer well-polished uncoated carbide with flood coolant. Brass, copper, bronze Uncoated or ZrN Soft, low-melt materials. Uncoated cuts cleanly; ZrN for production runs. Plastics, polymers Uncoated single-flute or 2-flute, polished Coating not required. Sharp uncoated edges and good chip evacuation are what matter. Carbon fibre composite, graphite CVD diamond or DLC Extremely abrasive. Diamond coating gives 10–20× tool life vs uncoated. Wood, fibreglass DLC or uncoated polished DLC reduces resin adhesion in fibreglass. Length classifications: stub, regular, long, extra-long End mill flute length is classified by reach beyond the shank: Stub — flute length roughly equal to or less than diameter. Maximum rigidity, minimum vibration. Use whenever depth allows. Regular (standard) — flute length roughly 2–3× diameter. The default workshop choice. Long — flute length 3–4× diameter. Reach when the part requires it; rigidity drops dramatically. Extra-long / extended — 4× diameter or more. Specialist tools for deep pockets and reach into restricted areas. Treat with care. The rigidity rule: tool deflection scales with the cube of stick-out length. Doubling the reach increases deflection 8×. Always pick the shortest end mill that gets to the depth you need. If you must reach deep, drop down to a smaller-diameter long-reach tool with reduced cutting parameters, or use a specialist extended-shank cutter with reduced flute length (only the bottom is cutting; the rest is a smooth necked-down stub for clearance). Climb milling vs conventional milling The two milling directions describe how the cutter rotates relative to the feed direction. Climb milling (down milling) — the cutter rotates with the feed direction. Each tooth enters the work taking maximum chip thickness, then exits taking zero. Cutting force pushes down on the part. This is the modern CNC default. Conventional milling (up milling) — the cutter rotates against the feed direction. Each tooth enters taking zero chip thickness and ramps up to maximum at exit. Cutting force pushes the part up and away. The default on older manual mills with backlash in the feed screws. Aspect Climb milling Conventional milling Tool life Better — tooth enters into existing chip Worse — tooth rubs and work-hardens before cutting Surface finish Better Worse Chatter Lower Higher Required setup Anti-backlash leadscrew or zero-backlash CNC drives Tolerates backlash in feed Risk Can grab on a manual mill with backlash, pulling work into cutter Lower risk on manual mills Best for CNC machining, finishing passes, all serious production Manual mills with backlash, very thin parts where downward force would lift them The "thick to thin" principle (Practical Machinist thread on this is a classic): in climb milling each tooth's chip starts thick at entry and thins to zero at exit — this means most cutting energy is spent at the start of the tooth's arc when the cutting edge is sharp and unloaded; by the time the tooth is rubbing it's only sliding along an already-cut surface. Conventional milling reverses this — the tooth rubs first, then cuts. The rubbing portion work-hardens stainless steel and burns the cutting edge. Climb whenever your machine allows it. Speeds and feeds basics Speeds and feeds are the most important runtime variable for end mills. They are also where most beginner-level mistakes happen — too slow burns the cutter, too fast breaks it, wrong chip load polishes the edge instead of cutting. The two key numbers: Cutting speed (V_c, also SFM in imperial) — how fast the cutting edge passes through the material, in metres per minute (m/min) or surface feet per minute (sfm). Set by work material and tool material/coating combination. Chip load (f_z, feed per tooth) — how much material each cutting tooth removes per pass, in millimetres per tooth (mm/tooth) or thou per tooth. Set by tool diameter, material, and operation type. Convert to RPM and feed rate: RPM = (V_c × 1,000) ÷ (π × D) where V_c is in m/min and D is cutter diameter in mm Feed rate (mm/min) = RPM × number of flutes × chip load (mm/tooth) Worked example: 10 mm 4-flute carbide end mill cutting mild steel at V_c = 100 m/min and chip load 0.05 mm/tooth. RPM = (100 × 1,000) ÷ (3.14 × 10) = ~3,180 RPM Feed rate = 3,180 × 4 × 0.05 = 636 mm/min Chip thinning — when radial engagement is less than half the cutter diameter (any peeling/finishing pass), the actual chip thickness produced is less than the programmed feed per tooth. To keep the chip at the correct thickness for the cutting edge, you need to increase the programmed feed per tooth proportionally. Most CAM software handles this automatically; manual programmers should know about it because under-fed cutters at low radial engagement rub instead of cut, polishing the edge into failure. For full reference tables on cutting speeds for HSS, cobalt, and carbide across common materials, see our Cutting Speeds and Feeds Chart. For cutting fluid selection and lubrication, see our Cutting Fluids Guide. End mill applications: side milling, slotting, profiling, ramping, helical, plunging Operation Description Best end mill Side milling (peripheral) Cutting on the periphery — light radial engagement, full axial 4-flute (steel) or 3-flute (aluminium) at high feed; fewer flutes for full radial engagement Slotting Full-diameter engagement, full chip valley load 2-flute (Al) or 3-flute (Al), 3- or 4-flute (steel). Centre-cutting required. Profiling / contouring Following a 2D or 3D path Square (2D), corner radius (2D with strong corners), ball nose (3D) Pocketing Hollowing out an enclosed shape Square or corner radius, plus a smaller-diameter end mill for tight internal corners Ramping Diagonal entry — cutter enters at an angle rather than plunging Centre-cutting end mill at a shallow ramp angle (typically 1–5°) Helical interpolation Spiral entry path — cutter follows a helix down into the work Centre-cutting end mill. The modern preferred entry for pockets — kinder to the tool than plunging. Plunging Cutting straight down like a drill Centre-cutting end mill only. Slow feed. Better to drill a pilot hole if depth is significant. Trochoidal milling Small-diameter circular tool path with high feed 5- to 7-flute high-feed end mill at light radial engagement and large axial depth Centre-cutting clarification: Not every end mill can plunge straight down. Centre-cutting end mills have flutes that cross the cutter centreline; non-centre-cutting do not — they have a small uncut zone in the middle and will simply spin without cutting if plunged. Most modern 2-, 3-, and 4-flute end mills are centre-cutting. Check the catalogue spec or the manufacturer's drawing if it matters for your application. End mill failure modes — what they tell you End mills don't usually fail without warning. The way they fail tells you what to change. Failure mode Cause Fix Edge wear (uniform) Normal end-of-life Replace tool. Check tool life is matching expected. Chipping (small cutting-edge fragments lost) Vibration, interrupted cut, hard inclusions in material, brittle coating mismatch Reduce chip load, check rigidity, switch to tougher grade or coating. Variable helix for chatter. Built-up edge / chip welding Wrong coating for material (Al-bearing on aluminium), insufficient cutting fluid, too low cutting speed Switch to uncoated/ZrN/DLC for aluminium. Increase speed. Use cutting fluid. Thermal cracks (comb cracks across edge) Thermal shock — interrupted coolant, poor coolant flow on hot work Use flood coolant or air blast consistently; avoid interrupting coolant during cut. Catastrophic breakage Excessive deflection, entered work too aggressively, tool stick-out too long, hit hardened inclusion Shorter tool, reduce engagement, ramp/helical entry instead of plunge, check work-holding. Polished/glazed edge with no cutting Chip load too low (rubbing instead of cutting); especially common at low radial engagement without chip thinning compensation Increase chip load. Apply chip thinning compensation. Check spindle speed isn't too high. Deflection-driven taper Tool flexing under sideload; long-reach tools, undersize cutters in heavy cuts Shorter tool, reduce stepover, use stiffer holder (hydraulic or shrink-fit), spring passes for finish. Building a starter end mill set for an Australian workshop For a small-to-medium AU workshop running a CNC mill (or a manual mill with DRO), a sensible starter end mill set looks like this. Adjust quantities based on actual workload — these are practical core picks, not exhaustive. For steel and stainless work (4-flute, TiAlN coated, solid carbide): 6 mm — for small pockets, slot work, fine detail 10 mm — general-purpose workhorse 12 mm — heavier roughing and faster removal 16 mm or 20 mm — only if your machine and work justify it For aluminium work (3-flute, uncoated or ZrN, solid carbide, high-helix): 6 mm — small details 10 mm — general-purpose Al workhorse 12 mm — bulk removal in Al For 3D contouring and finishing (ball nose, 2- or 4-flute carbide, TiAlN for steel, uncoated for Al): 6 mm ball nose 12 mm ball nose Specials worth having: One 10 mm corner radius (R0.5 or R1) end mill — when corners need to be strong, not sharp One 8 mm or 10 mm chamfer end mill (45°) — for breaking sharp edges in the same operation as profile One small (3–4 mm) HSS end mill — for delicate jobs where carbide breakage risk is higher than tool-life cost Budget vs premium decision: For high-volume production, premium brands (Sutton, Iscar, Sandvik, Garant, OSG) repay their cost in tool life and predictable performance. For low-volume jobbing, hobby work, prototyping, and one-offs, mid-tier branded tools (Sutton, Bordo) at sensible prices are the sweet spot. Cheap unbranded carbide can work for very simple aluminium cuts but tool-life and dimensional accuracy are unreliable — fine for hobby, risky for paid work. Buying end mills in Australia: brands, where to buy, common mistakes Australian-made brands Sutton Tools — manufactured in Thomastown, Victoria. Strong VHM (solid carbide) range, comprehensive HSS / cobalt range, well-priced for what you get. Sutton's E-series and VHM TiAlN are workshop staples in AU. AIMS stocks Sutton across square, ball nose, corner radius, and corner chamfer. Bordo — Australian-distributed range, stronger on HSS and cobalt for hand-mill and light CNC use. Good value for non-production work. Premium imports — Sandvik Coromant (Sweden), Iscar (Israel), Mitsubishi (Japan), Walter (Germany), OSG (Japan), Garant (Germany). All available in AU through specialist tool distributors. AIMS can source most premium imports on request — call for pricing and availability. Common buying mistakes: Wrong shank tolerance — modern collets and hydraulic holders need h6 ground shanks. Generic "carbide end mill" listings sometimes ship h7 or worse, which won't run true in a precision holder. Wrong overall length for the work — buying long-reach when stub-reach would do means the tool will deflect. Cube-of-length deflection rule applies. Buying a coating mismatched to the material — TiAlN is the common shop spec; using it on aluminium will burn the tool fast. Centre-cutting confusion — assuming a non-centre-cutting end mill can plunge. Always check. Cheap unbranded carbide — quality varies wildly. May be fine for soft material; rarely fine for production stainless. Mixing imperial and metric without converting — feed and speed charts are often in SFM and IPT (imperial) while AU shops run mm/min. Convert before programming. For PPE while milling: safety glasses are mandatory (see our Safety Glasses Guide for AS/NZS 1337 selection), and hearing protection for prolonged spindle work (see our Hearing Protection Guide). Cutting fluid selection drives tool life as much as feed and speed — see our Cutting Fluids Guide for selection by material. End mills at AIMS Industrial AIMS stocks 50+ end mills across the workshop-essential geometries: Square End Mills — Sutton VHM TiAlN (E562, E604), Sutton HSS, Bordo HSS cobalt — metric and imperial Ball Nose End Mills — Sutton solid carbide TiAlN — metric, for 3D contouring Corner Radius End Mills — solid carbide, common radius sizes Corner Chamfer End Mills — combined milling and edge-break Full End Mills & Milling Cutters collection — browse the full range For specialty geometries (T-slot, dovetail, thread mill, drill mill, tapered, specialty Al-only, premium imports), call us on (02) 9773 0122 or use our contact page. We work with a network of premium tooling suppliers and can source most specs. Related AIMS Selectors This guide pairs with AIMS's other cutting-tool selectors. Use them together for complete coverage: Drill Bit Size Selector — every metric drill diameter linked to AIMS-stocked SKU. Drill Bit Selection Guide — choose drill bit type by material and application. Tap Drill Size Selector — every thread size linked to tap + matching drill SKU. Tap & Die Selection Guide — choose tap type by material, hole type, and machine. HSS vs Carbide End Mill — when to upgrade from HSS to solid carbide. Cutting Speeds & Feeds Reference — Vc and feed rate per material and tool diameter. Cutting Tool Materials — HSS, cobalt, carbide, PCBN, PCD compared. Cutting Tool Coatings — TiN, TiAlN, AlCrN, Helica, when each matters. Cutting Tool Troubleshooting — chipped edges, vibration, poor finish, snapped tools. Or browse the full end mills range, square end mills, ball nose end mills, corner radius end mills, and corner chamfer end mills — Sutton, Bordo and specialty brands in stock for next-day Australia-wide dispatch from our Milperra warehouse.Frequently Asked Questions What is the difference between a drill bit and an end mill? A drill bit only cuts on its tip and is designed to plunge straight down into the work, evacuating chips up the flutes. An end mill cuts on both its end and its sides — it is designed to be fed sideways past the work, removing material in a 3D path. Some end mills (centre-cutting types) can plunge like a drill in addition to side-milling, but most milling work is sideways feed. End mill flutes are designed for sideways chip evacuation rather than vertical hole evacuation. Is a 2-flute, 3-flute or 4-flute end mill better for aluminium? For aluminium use 2-flute or 3-flute. Aluminium chips are large and gummy, and the deeper flute valleys of 2- and 3-flute end mills evacuate them cleanly. A 4-flute end mill in aluminium will pack the flutes with chips, weld a chip back to the cutter, and either burn the cutting edge or break the tool. Modern preferred choice in production aluminium machining is 3-flute — best balance of chip room and feed rate. Why shouldn't I use a TiAlN or AlTiN coated end mill on aluminium? TiAlN and AlTiN coatings contain aluminium oxide. When cutting aluminium, the chips have strong chemical and mechanical affinity for the aluminium-bearing coating — chips weld to the cutting edge, creating a "built-up edge" that breaks off taking carbide with it. The cutter fails fast. For aluminium use uncoated polished carbide, ZrN coating, or DLC coating — none of which contain aluminium and so don't have the affinity problem. Forum consensus across Practical Machinist and r/Machinists is unanimous on this: stay away from TiAlN/AlTiN on aluminium. What is the best coating for end mills cutting stainless steel? TiAlN or AlTiN is the standard coating, paired with variable helix and unequal flute spacing geometry to break up the cutting harmonic that work-hardens stainless. The combination of high-temperature coating (handling the heat that doesn't transfer well to short curly stainless chips) and irregular flute timing (preventing chatter that work-hardens the cut surface) is the modern recipe for 304, 316, and 17-4 PH machining. Most premium end mill manufacturers offer this configuration as a "stainless steel" or "performance" line. What is the difference between HSS, cobalt and carbide end mills? HSS (high-speed steel) is the cheapest and most forgiving — it tolerates shock, can be reground, and is fine for hand mills, hobby CNC, and soft materials. Cobalt HSS (M35, M42) is HSS with cobalt added for better heat resistance — used for stainless steel and harder materials at HSS speeds. Solid carbide is the production standard — much harder, much more heat resistant, allows 3–10× higher cutting speeds — but it is brittle and shatters under shock or heavy interrupted cuts. For CNC production, carbide. For manual or hobby, HSS or cobalt. Can I use an end mill to drill straight down? Only if it is a centre-cutting end mill. Centre-cutting types have flutes that meet at the tool centreline and can plunge directly. Non-centre-cutting end mills have a small uncut zone in the middle — they will simply spin without cutting if plunged. Most modern 2-, 3- and 4-flute end mills are centre-cutting; many 5+ flute end mills are not. Check the catalogue spec. Even with a centre-cutting end mill, ramping or helical entry is kinder to the tool than vertical plunge, and produces a better finish. What does the helix angle of an end mill do? The helix angle is the angle of the flutes relative to the tool axis. Low helix (15–30°) gives the strongest tooth and lowest axial pull — used for hard materials and roughing. Standard helix (30°) is the general workhorse. High helix (38–45°) gives a smooth shearing cut with excellent surface finish and lower cutting forces — the default for aluminium and finishing in steel. Variable helix (e.g. 35°/37°/35°/37°) breaks up tooth-pass harmonics and is the standard for stainless steel and titanium where chatter is a problem. What is climb milling and is it better than conventional milling? Climb milling rotates the cutter with the feed direction — each tooth enters the work at maximum chip thickness and exits at zero. Conventional milling rotates against the feed direction. On modern CNC with anti-backlash drives, climb milling gives better tool life, better surface finish, and lower chatter — it is the modern default. On an older manual mill with backlash in the feed screws, climb milling can grab the work and pull it into the cutter; conventional milling is safer in that case. Once you have CNC drives or anti-backlash hardware, switch to climb. What is chip thinning and when does it matter? Chip thinning happens at light radial engagement (under about half the cutter diameter, common in peeling and finishing passes). The actual chip thickness produced is less than the programmed feed per tooth, because each tooth only contacts the work for a small arc. To maintain the correct chip thickness for the cutting edge to actually cut (rather than rub and polish), you need to increase the programmed feed per tooth proportionally. Most CAM software handles this automatically. Manual programmers should know that under-fed cutters at low radial engagement glaze instead of cut. What is the difference between a square end mill and a ball nose end mill? A square end mill has a flat bottom with sharp 90° corners — used for general milling, slotting, profiling, and any operation needing a flat-bottomed cut with sharp internal corners. A ball nose end mill has a hemispherical full-radius end — used for 3D contouring, mould and die work, and finishing curved surfaces. A ball nose always leaves a small scallop on a flat surface (the tool can't make a flat-bottomed cut), so you choose between them based on whether the work needs flat bottoms (square) or 3D curvature (ball nose). When should I use a roughing end mill? Use a roughing end mill (corn-cob serrations along the cutting edge) when you need to remove a lot of material fast and surface finish is going to be cleaned up by a finishing pass anyway. The serrations break the chip into small pieces, evacuate efficiently, and reduce cutting forces compared to a smooth-edged end mill at the same feed. Use a finishing end mill (smooth flutes, often higher flute count) for the final pass. The two-tool roughing-then-finishing strategy is standard for any non-trivial 3D job. How do I work out the right speed and feed for an end mill? Start from cutting speed (V_c) for the material/coating combination, in m/min. Convert to RPM: RPM = (V_c × 1,000) ÷ (π × D), where D is the cutter diameter in mm. Multiply RPM by the number of flutes and the chip load (mm/tooth) to get feed rate in mm/min. The hard part is picking V_c and chip load — these come from manufacturer charts or experience. See our Cutting Speeds and Feeds Chart for full reference tables across HSS, cobalt, and carbide on common materials. Why are odd-flute (3, 5, 7) end mills said to reduce chatter? Even-flute end mills have a regular tooth-strike pattern that can resonate with the natural frequency of the workpiece, the tool, or the spindle, producing chatter. Odd flute counts (3, 5, 7) — and especially variable helix with unequal flute spacing — break up that regular harmonic. The asymmetry means no single frequency dominates, and resonant chatter is much harder to set up. On long-reach work, thin-wall parts, or stainless and titanium, switching to an odd-flute end mill (or a variable-helix one) often dramatically reduces chatter without changing speed or feed. How long should an end mill last? Tool life depends entirely on material, speed, feed, depth of cut, coolant, machine rigidity, and how hard you push. Sensible production targets for a quality solid carbide end mill in steady ferrous machining are typically 60 to 240 minutes of cutting time. In aluminium, tool life can run into many hours per tool. In titanium or hardened steel, life can drop to 15–30 minutes. If you're seeing tool life under 30 minutes in mild or stainless steel, something is wrong — usually too high a chip load, wrong coating, insufficient coolant, or a rigidity problem. Track tool life on your work — it will tell you when something has changed. What are the most-used end mills in a general workshop? The 80/20 rule is real for end mills. In most general AU workshops, the bulk of work is done by: 4-flute solid carbide TiAlN-coated end mills in 6 mm, 10 mm, and 12 mm for steel and stainless; 3-flute solid carbide uncoated or ZrN-coated in 6 mm and 10 mm for aluminium; one 10–12 mm corner radius end mill for strong-corner work; one 6 mm and one 12 mm ball nose for any 3D contouring. A few HSS end mills in 4–8 mm round out the kit for delicate work where carbide breakage is a concern. AIMS keeps these popular sizes in stock — see our End Mills collection. If you need to drill into hardened or abrasive material, our carbide drill bits are the right tool for the job. AIMS Industrial stocks sutton tools — see the full range for trade and industrial use. Need ball nose end mills? Browse the AIMS range at ball nose end mills. Related AIMS Industrial Engineering References For deeper engineering data behind end mill selection — material identification, RPM and feed rates by material, coatings and tool material families — see the AIMS Phase 4 master references. Phase 4 master references (universal engineering data): Workpiece Material Cross-Reference Chart — SAE / AISI / DIN / JIS / AS/NZS equivalents across 20 material groups Cutting Speeds & Feeds Reference — RPM and feed rate by material and tool type — drilling, milling, tapping, reaming Cutting Tool Materials Guide — HSS, HSS-Co, PM-HSS, solid carbide, PCBN and PCD explained Cutting Tool Coatings Guide — TiN, TiCN, TiAlN, AlCrN and premium coatings with application matrix Cutting Tool Troubleshooting Guide — 33 symptoms diagnosed across drills, taps, endmills, reamers and bandsaw blades Metric to Imperial Conversion Chart — mm, inches, drill # and gauge cross-reference Sister selection guides in the AIMS application cluster: AIMS Drill Bit Selection Guide — HSS / cobalt / carbide / masonry / tile selection by material and application AIMS Tap & Die Selection Guide — Hand, spiral point, spiral flute and forming taps — metric and imperial For purchase advice, technical questions or items not currently listed, ring AIMS Industrial on (02) 9773 0122 or use the contact page. 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Choosing Between High-Speed Steel and Carbide Tools
(Taken from this post by Sutton Tools. Republished with permission. Edited for point of view, recency and relevance.) You may be wondering: “Should I use high-speed steel or carbide for my solid rotary tools, like endmills, drills and taps?” There’s no quick answer, because there are a lot of factors involved: Tool size Depth of cutting Required material removal rate Tool life Cycle time Cost Each type of component also presents different challenges, including design, size, batch quantity, material type and hardness. Sutton Tools General Manager, Jeff Boyd, discusses both to help us understand when to use which one. In this article, we discuss: Characteristics of HSS vs carbide HSS vs carbide for drilling HSS vs carbide for tapping HSS vs carbide for milling HSS powder metallurgy (HSS-PM) HSS versus carbide: General characteristics In general, the main characteristic of all high-speed steels is a high working hardness with excellent toughness. HSS tools also cost less than carbide tools and are often a good solution in ‘high-mix, low-volume’ applications. Carbide is much harder, so it has a longer tool life and faster cutting data than conventional HSS. The downside of that hardness is brittleness, so the cutting edge on carbide tools can quickly fracture or chip in certain situations. HSS can really excel over carbide due to its toughness in applications such as where: • The component to be machined is poorly clamped• Set-up is not rigid• The tool is a long-reach type with excessive overhang from the tool holder• Poor machine-spindle condition Let’s look at three common machining operations – drilling, tapping and milling – to gain a better understanding of when to use HSS or carbide tools. Drilling Carbide drills are generally used for high-volume hole production, where the higher tool cost can be justified on a cost-per-part basis. For deep high-volume holes, they are often available with internal coolant ducts, resulting in longer tool life and stable production. Use of through-the-spindle and high-pressure coolant offers excellent chip evacuation, particularly in deeper holes (>3xD), and is the most effective method for cooling the edge in cut. Carbide drilling is also the fastest way to produce holes in a wide range of metals, due to the higher cutting speeds and feeds possible. However, it’s important to know that in some higher Ni-Cr alloy steels (such as stainless steels), although the hole can be produced with high speeds, the condition of the walls of the hole can quickly work-harden. This can lead to other issues in the machining process, particularly if the hole is to be internally threaded; the tool life of the tap will be considerably shortened since it will be trying to cut through a hardened skin or surface. Importantly, carbide tools can be justified in low-volume production for their higher hardness because they enable harder materials to be machined, potentially up to 70+HRC. HSS drills have a very wide range of uses – from handheld applications to CNC machining in short batch runs – due to their toughness and lower cost. They are ideal for less rigid applications such as hand-held drilling, stack drilling and deep hole drilling where an internal coolant supply is not available. There are various geometries available for specific material grades to really cut through the material and leave it in its best annealed condition. Ideal for pre-tap drilling in stainless steel, HSS drills can really benefit the life of the tap when the right geometry is used to produce the hole! Tapping HSS tools are typically the first choice for tapping. They are by far the most common for internal thread production, with many HSS-PM versions available more recently for the various CNC machine tapping applications, different thread types and materials groups. Given their toughness, HSS tapping tools are also common in the Maintenance-Repair and Operations (MRO) industries, with hand taps or straight flute taps the most widely used. HSS taps are even used in large volume applications. In difficult-to-machine material applications, HSS-PM taps are still the first choice due to the process stability they offer. Carbide taps are not as popular due to the brittleness of carbide. It tends to chip in most tapping applications, particularly in blind holes. Carbide will fracture in steel applications at full depth, when the tap reverses and breaks the chips that were produced from the down cut in order to back out of the hole. As mentioned earlier, HSS has superior toughness over carbide, and in the tapping process this is very important. Due to the nature of tapping being a ‘slow speed, high feed’ type process, and with the spindle slowing-then reversing at the full thread depth and breaking the chip produced from the down stroke of the machine, it’s this action that the HSS toughness characteristic performs superior to carbide. That said, carbide taps can be used for some specific applications, including: • Tapping hardened steel, with a specific geometry that has negative cutting angles• Tapping high-silicon aluminium (AlSi), as the silicon content makes the material quite abrasive and carbide offers the best resistance• Some through-hole tapping applications in steel are possible, but only with specifically suitable geometry Carbide forming taps can also be justified in high-volume applications. Since there are no cutting edges, you can achieve long tool life without the possibility of chipping and thus justify the higher tool cost. They are quite popular in ADC12 (AlSi 8-12%) automotive aluminium applications. Milling Carbide endmills are by far the most popular because they offer the best Metal Removal Rates (MRR). Solid carbide endmills have become the first choice, given the variable helix designs combined with CAM packages that provide tool paths to suppress chatter from the natural vibration produced in a milling cut. Milling strategies such as trochoidal methods are now quite common. HSS endmills still have a place, such as for manual milling machines, smaller volumes, less rigid set-ups, and the like. HSS-PM: Best of both worlds? As noted, conventional grades of HSS have lower cutting speeds applied, but in recent times, HSS-PM (Powder Metallurgy) has been developed to bridge the gap between HSS and carbide tools. Simply put, HSS-PM is produced from a powder similar to carbide. This produces a finer grain structure which allows PM tools to reach a higher hardness than HSS, whilst still maintaining their excellent toughness. This means you can have a tool that will last longer than standard HSS and which can be used with high hardness materials, thereby closing the gap between the HSS and carbide tooling. There are also some needs in rough milling applications for HSS-PM due to the heavy style of cuts taken per pass. For example, when an aerospace component has a long cycle time, producers like to run their machines ‘lights-out’ overnight to do a lot of the roughing operations. They are not, however, confident to run with carbide endmills due to their brittleness, and this is where HSS-PM roughing endmills perform best. Whatever your application and operational considerations, it all comes down to finding the right solution. Shop for Sutton HSS and carbide tools now. AIMS' Note on Safe Use of Power Tools Inspection: Before using any tool, carefully inspect it for cracks, chips, loose handles, worn / mushroomed heads or any other signs of damage. Damaged or defective tools may cause harm! Ensure all guards are in place. Right tool for the job: Make sure you understand the intended purpose of each tool and choose the correct one for your specific job. Don't try to make a screwdriver work as a pry bar or a wrench as a hammer. Safe handling: Carry sharp tools pointed down and away from your body. Never carry tools in your pockets where they can cause injury. When passing a tool to someone, extend the handle first. PPE: Wear safety glasses or goggles to protect your eyes from flying debris. Consider gloves depending on the tool and task to prevent cuts or blisters but without compromising comfort, dexterity and protection. If working with noisy tools, wear ear protection. Maintenance: Keep your tools clean, sharp and properly maintained. Store them in a safe and organised place when not in use. During use: Maintain a firm grip and good balance while using the tool. Avoid distractions and focus on the task. Don't force the tool; let it work at its own pace. Keep cords clear of the cutting path and away from heat or sharp objects. Never leave a running tool unattended. When finished, turn the tool off, unplug it, and wait for any moving parts to stop completely before cleaning or making adjustments. This blog's sub-topics Our Tap Types guide covers every cutting and forming tap variant with material-specific selection rules. People Also Ask — HSS vs Carbide Cutting Tools Q: When should I choose HSS over carbide cutting tools? High-speed steel (HSS) is the better choice when: (1) using a hand drill, portable drill press, or any setup with significant runout or vibration — carbide is brittle and will chip under these conditions; (2) machining interrupted cuts such as keyways, splines, or cross-holes — HSS handles intermittent impact better than carbide; (3) the workpiece material is tough or stringy (e.g., copper alloys, some stainless grades) where HSS's toughness prevents chipping; (4) tooling cost per use matters more than tool life — HSS drills, taps, and endmills are significantly cheaper than carbide equivalents. Q: What is the speed advantage of carbide over HSS? Solid carbide tooling can typically run at 3–5× the cutting speed (Vc) of equivalent HSS tools in the same material. In mild steel (e.g., 250 MPa), an HSS endmill might run at 25–35 m/min while a carbide equivalent runs at 80–120 m/min. In aluminium, HSS runs at 60–90 m/min while carbide can exceed 300 m/min. This speed advantage translates directly to shorter cycle times and higher production output. The caveat is that realising carbide's speed potential requires a rigid machine tool with minimal vibration and accurate coolant delivery. Q: Can I use carbide drill bits in a hand drill? Solid carbide drill bits are generally not recommended for hand drills. Carbide is extremely hard but brittle — it is highly sensitive to the bending and shock loads that occur with the slight flex and misalignment inherent in hand drilling. A carbide drill subjected to lateral force during entry will chip or snap. Carbide-tipped masonry drills are designed for percussion drilling and are an exception. For hand drilling in steel, cobalt HSS (HSS-Co) is the better choice — nearly as hard as carbide in terms of heat resistance but much more tolerant of the conditions a hand drill creates. Q: Does HSS-Co 8% outperform HSS-Co 5% for stainless steel? HSS-Co 8% (M42 grade) offers higher hot hardness than HSS-Co 5% (M35 grade), making it more resistant to the heat generated when machining work-hardening materials like 304 and 316 stainless steel. In demanding stainless applications — deep holes, heavy feeds, or interrupted cuts — HSS-Co 8% will hold its edge longer and run at slightly higher speeds than HSS-Co 5%. However, HSS-Co 8% is also more brittle and more expensive. For most stainless steel drilling in fabrication workshops, HSS-Co 5% (such as Sutton Tools' Blue Bullet cobalt series) provides an excellent cost-performance balance. Q: What does TiAlN coating do for carbide and HSS tools? Titanium Aluminium Nitride (TiAlN) coating significantly increases the surface hardness and oxidation resistance of both carbide and HSS tools. It performs best in dry machining or high-speed machining with minimal coolant because TiAlN forms a hard aluminium oxide layer at high temperatures that acts as a thermal barrier, protecting the cutting edge. TiAlN is particularly effective on carbide endmills in steels, cast iron, and titanium alloys. Important caveat: TiAlN reacts chemically with aluminium workpieces — use an uncoated or TiN-coated tool for aluminium to prevent built-up edge and tool damage. Need key steel? Browse the AIMS range at key steel.
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