Drill Bit Types Guide

Grab a handful of drill bits from any toolbox and you will likely see several different colours, finishes and shapes. Ask most people what those differences mean and the answer comes back the same: "black ones are for wood, gold ones do everything, red tip is for concrete." That is wrong — and it is the kind of wrong that destroys bits, scorches workpieces and wastes money on every job.

The colour of a drill bit tells you nothing about what material it cuts. It tells you about the coating applied to the steel. The shape of the tip, the geometry of the flutes, and the material the bit is made from — those are what determine correct application. This guide explains all three, covers every common drill bit type used in Australian trade and industry, and gives you a reference table you can come back to when the job in front of you is not the one you normally run.

Already know the type and need the size? See our Drill Bit Size Chart: Metric, Imperial & Fractional for pilot hole, clearance hole and tap drill size reference. For a fast material-to-bit selection reference, see Choosing the Right Drill Bit.

How drill bits are classified — the two-axis framework

Most guides list drill bit types by name alone and leave the reader confused about the difference between "cobalt" and "HSS" when both look like twist bits. The reason for the confusion is that drill bits have two independent classification axes, and they are often discussed as though they are the same thing.

Axis 1 — Application type (shape and geometry): what the bit is designed to do. Twist bits, brad-point bits, masonry bits, spade bits, countersinks, and SDS bits are all application types. This is primarily about tip geometry and flute design.

Axis 2 — Bit material and coating: what the cutting edge and body are made from. HSS, cobalt, carbide-tipped, black oxide, TiN-coated. This determines how hard the bit is, how much heat it tolerates, and how long it lasts.

These axes are independent. A twist bit can be plain HSS, cobalt, TiN-coated, or carbide-tipped. A masonry bit is always carbide-tipped, but the steel body can vary in grade. Understanding both axes before you buy means you match the right geometry to the job and the right material to the hardness of what you are cutting into.

Drill bit materials and coatings — what the colour actually means

This is the section most guides skip. It is also where most bit selection mistakes happen, because marketing has deliberately blurred the line between coating and capability for decades.

The resharpening issue with coated bits: TiN and TiAlN coatings are applied after grinding. If you resharpen a coated HSS bit, you grind away the coating at the cutting edge. From that point on you have an uncoated HSS bit wearing a TiN-coloured shank. For occasional-use bits this rarely matters. For high-volume metalwork, cobalt bits resharpened correctly remain cobalt throughout — because the cobalt is in the steel itself, not on top of it.

Twist drill bits — the universal baseline

Twist bits are the most common drill bit in any toolbox. Two helical flutes run the length of the bit, clearing swarf from the hole as the bit advances. The point angle, flute helix angle and shank type vary by application.

Point angle: 118° vs 135°

The point angle is the included angle at the tip of the bit. Standard twist bits to DIN 338 specification have a 118° point angle — suitable for general-purpose metalwork and timber. A 135° split-point (also called "web thinned" or "self-centring") has a wider, flatter tip that requires less pressure to start and is less likely to walk on a smooth surface. The split geometry also reduces the "chisel edge" at the centre of a 118° bit, which does not cut but instead ploughs material. For hard metals and sheet metal, 135° split-point bits are preferred.

Shank types

Round shank is standard for keyed and keyless drill chucks. Hex (1/4" hex) shank fits quick-release impact drivers and bit holders — suitable for lower-torque applications in timber and soft metals. SDS-plus and SDS-max shanks are specific to rotary hammer drills and are covered separately below.

What twist bits cut well: mild steel, structural steel, aluminium, brass, copper, cast iron (with cobalt), plastics, softwood and hardwood. They will cut masonry in a pinch on a single use but the carbide tip of a dedicated masonry bit is essential for anything beyond a shallow hole.

What twist bits do not do well: clean entry and exit holes in timber (brad-point is better), masonry drilling beyond occasional light use, large-diameter holes (spade bit or hole saw is more efficient above 12–13 mm in timber).

Masonry drill bits — concrete, brick, render and block

Masonry bits are identified by a flat, spade-shaped tungsten carbide tip brazed onto a steel flute body. The tip does not shear material the way a metal bit does — it fractures and pulverises it with a combination of rotation and percussive hammer action. Trying to use a masonry bit without hammer mode is significantly less effective for anything harder than soft brick.

When standard masonry bits are sufficient: soft brick, mortar, render, lightweight block, light-gauge plasterboard mounted to masonry. A standard drill (not rotary hammer) with hammer mode is adequate for holes up to approximately 8 mm in standard brick.

When a rotary hammer (SDS) is required: holes larger than 8–10 mm in brick, any diameter in concrete, reinforced concrete, dense block. The independent hammering action of an SDS rotary hammer generates significantly more impact energy than the hammer mode of a standard drill. Forcing standard masonry bits at large diameters in concrete with a regular drill is slow, burns out the drill motor, and often damages the bit.

What about rendered brick? Render is typically a sand-and-cement mix and is softer than the substrate beneath it. A standard carbide-tipped masonry bit drills through render easily. The question is what lies beneath: clay brick — standard masonry bit with hammer mode is fine. Dense concrete block — switch to an SDS-plus bit in a rotary hammer. If you are uncertain, probe with a small masonry bit first before committing to a larger diameter.

Diamond core drill bits are used for large-diameter holes in concrete and masonry — cable conduit penetrations, pipe penetrations, structural anchor sockets. These are wet-cutting bits that require a water feed to cool the diamond segments. They are used with a dedicated core drill stand or core drill machine, not a handheld SDS drill.

Wood drill bits — four types for four jobs

Timber drilling is where bit geometry matters most. An HSS twist bit will cut timber — but it tends to wander on entry, tear the wood fibres on exit, and produce a rougher hole than a wood-specific bit. For rough framing and cable runs where hole quality is irrelevant, HSS is fine. For joinery, cabinetmaking and any work where the hole is visible or dimensionally critical, the correct bit makes a visible difference.

Brad-point bits (lip-and-spur bits)

Brad-point bits — also called lip-and-spur bits in Australian trade catalogues — have a centre point that locates the bit precisely before the outer spurs score the wood fibres. This eliminates wandering on entry and produces a clean, defined edge at both entry and exit. The centre point also allows accurate hole placement without a centre punch.

Best for: hardwood and softwood where hole quality matters — furniture making, joinery, dowel holes, hinge prep. Sizes typically 3–25 mm. Not for use in metal.

Spade bits (flat wood / paddle bits)

Spade bits are a flat steel paddle with a central point and two cutting edges. They are fast and effective for large-diameter holes (typically 16–38 mm) in softwood and plywood where speed matters more than hole quality — framing, running cables through joists and studs. They cannot drill overlapping holes and tend to produce tear-out on the exit face without a backing board. Not suitable for hardwood at high speed.

Best for: rough framing, electrical and plumbing rough-ins, large holes in pine and softwood framing.

Auger bits

Auger bits have a self-feeding screw tip that draws the bit into the work, deep spiral flutes for efficient chip clearing, and cutting spurs for clean entry. They are designed for deep holes in timber — post and beam connections, farm fencing, structural work. SDS-compatible auger bits are available for use with rotary hammers where high torque is needed in hardwood.

Best for: deep holes in hardwood and softwood, post boring, structural timber. Sizes typically 10–50 mm diameter, lengths to 460 mm and beyond.

Forstner bits

Forstner bits produce flat-bottomed, clean-sided holes. Unlike spade bits, a Forstner bit is guided by its rim rather than its centre point, which means it can drill holes that partially overlap a previous hole — something no other common bit type can do. It can also drill at angles to the surface and into the edge of a board without deflecting.

Best for: hinge mortises, shelf pin holes, woodworking joints, dowel sockets where a flat bottom is required. Sizes typically 10–50 mm. Slow cutting speed is normal — Forstner bits are precision tools, not speed tools.

Metal drill bits — HSS and cobalt

Both HSS and cobalt twist bits cut metal. The decision between them is about the hardness of the material and the volume of work being done.

Standard HSS (M2 grade): adequate for mild steel, structural steel, aluminium, brass, copper, and most non-ferrous metals. For occasional metalwork, good quality HSS bits — sharp, run at the correct speed with cutting fluid — will produce acceptable results across most metals encountered in trade work.

Cobalt HSS (M35 / M42): the correct choice for stainless steel, hardened steel, high-tensile bolts, spring steel, and cast iron. The cobalt addition allows the bit to maintain its edge at higher temperatures, which matters because these materials generate more heat during cutting. A standard HSS bit attempting stainless steel will work-harden the surface and blunt within seconds. Cobalt bits — run at correct speed with cutting fluid — cut stainless cleanly.

Stainless steel — the work-hardening problem: Austenitic stainless steel (the most common grade in Australian industry — 304 and 316) work-hardens under heat and pressure. If a drill bit is running too fast, pressed too hard, or is allowed to stop mid-cut and restart, it creates a hardened zone that defeats even cobalt bits. The correct technique is: slow speed (approximately 60–80 RPM for 6 mm+ holes), firm consistent feed pressure, continuous cutting fluid, and no pausing once you start. Pecking — lifting the bit and restarting — creates the hardened zone that makes the next pass impossible.

Spot weld drill bits deserve a specific mention as they have 400 searches per month in Australia. These are specialised twist bits with a small pilot point and a wider secondary cutting edge, designed to cut through one layer of sheet metal at a spot weld without penetrating the layer beneath. Used extensively in panel and body work. Not a general-purpose drill bit.

Cutting speeds for metal drilling (general guidance): The correct speed decreases as material hardness increases and as hole diameter increases. A 6 mm bit in mild steel might run at 800–1,200 RPM; the same diameter in stainless requires 200–400 RPM. A 12 mm cobalt bit in stainless might run as slow as 60–80 RPM. Cutting fluid — even a drop of thread-cutting oil — makes a significant difference in bit life and finish quality. For full coverage of cobalt drill bit grades, M35 vs M42 selection, stainless steel work-hardening technique and brand selection, see our Cobalt Drill Bit Guide.

Tile, glass and ceramic drill bits

Drilling glazed ceramic, porcelain and glass requires a fundamentally different approach to metal or masonry. These materials are hard and brittle — they shatter under impact. Hammer mode must never be used.

Carbide spear-point bits: The entry-level option for glazed ceramic tiles and glass. A ground tungsten carbide spear-shaped tip cuts by abrasion at low speed. Effective for glazed wall tiles and light ceramic. For unglazed porcelain (which is significantly harder) these bits wear quickly.

Diamond-coated bits: The correct tool for porcelain tile, dense ceramic and glass. Industrial diamond abrasive bonded to a steel or carbide core. Two forms: solid shank bits for small diameters (3–10 mm), and diamond core drill bits for larger diameters (15 mm+). Both require water cooling — either a continuous drip or a water dam made from putty around the drill point. Drilling porcelain dry with a diamond bit overheats the bond and destroys the bit prematurely.

Countersink drill bits

Countersink bits create a conical recess in a material so that a flat or oval-head screw sits flush with or below the surface. Available as standalone countersinks or as combined drill-and-countersink units that pilot the clearance hole and countersink in a single pass. For the dedicated lathe-tailstock variant — the 60° pilot-and-shoulder tool used to support work between centres on a lathe — see our Centre Drill Bit Guide, which covers DIN 333 forms, ANSI B94-11 sizes, and breakage prevention.

Point angle — a frequently missed detail: Countersink bits are manufactured at either 82° or 90° included angle. In Australia and most of Europe, metric screws use a 90° countersink. American-standard screws (Whitworth/UNC/UNF) typically use 82°. If you countersink at 82° for a 90° metric screw, the screw head will sit proud of the surface. Check your screw specification before selecting the bit. Most Australian hardware-store countersink sets are 90° for metric screws.

Countersinks are available in HSS for timber and soft metals, and carbide for harder materials. For high-volume cabinetry work, adjustable stop-collar combined drill-and-countersink sets allow consistent depth on every hole.

Countersink drill bits in Australian searches: "countersink drill bit" generates 1,700 searches per month in Australia, making it one of the more actively searched drill bit types. The most common question is what angle to select — answered above.

SDS and SDS-plus drill bits — for rotary hammer drills

SDS (Slotted Drive System, standardised by Bosch) is a shank system specifically designed for rotary hammer drills. Unlike a standard chuck, SDS shanks are held by spring-loaded balls that engage slots in the shank, allowing the bit to slide axially by 3–6 mm while rotating. This independent axial movement allows the hammer mechanism to impact the bit directly without the impact force being transmitted through the chuck jaws.

SDS-plus: 10 mm shank diameter with two open and two closed slots. The most common SDS system in Australia, used for rotary hammers from approximately 2–8 kg (the typical site and workshop hammer drill range). Suitable for masonry bits 4–25 mm diameter and most standard core drilling applications.

SDS-max: 18 mm shank diameter, significantly larger grip area. Used in heavier rotary hammers (10 kg+) for large-diameter holes and demolition chiselling in reinforced concrete and hard stone. SDS-max bits are not interchangeable with SDS-plus without an adaptor.

Using an SDS bit in a standard drill: You cannot use an SDS-plus bit in a standard keyless or keyed chuck — the shank is designed for a specific retaining mechanism, not chuck grip. Adaptors exist but compromise the performance benefit. If you are regularly drilling masonry at 10 mm and above, a dedicated SDS rotary hammer is the correct tool.

SDS chisel and scraper attachments: Rotary hammer drills with an SDS-plus or SDS-max chuck also accept chisels and scrapers for light demolition, tile removal, and concrete breaking. These are not drill bits but use the same shank system.

Specialist drill bits — a practical reference

Step drill bits (uni-bits): Conical bits with stepped diameters, designed for sheet metal and thin-gauge steel. A single bit produces holes from approximately 4 mm to 30 mm without changing bits. See our dedicated Step Drill Bit Guide for full coverage of sizes, applications and technique.

Core drill bits: Hollow cylindrical bits, either SDS-mounted or used with a dedicated core drill machine, for large-diameter penetrations through concrete, masonry and brick. Wet diamond core bits require continuous water feed. Used for electrical and hydraulic conduit penetrations, pipe sleeves and structural anchor pockets. Diameters range from 25 mm to 250 mm and beyond.

Hole saws: Circular saw-tooth cutting rings mounted on an arbor with a pilot twist bit. Used in timber, plasterboard, thin sheet metal and plastic for diameters from 25 mm to over 150 mm. Bi-metal hole saws (HSS teeth on a flexible alloy body) cut sheet metal, PVC and timber. Carbide-tipped hole saws cut tile, fibre cement and harder materials. Hole saws are technically not drill bits, but they mount in a standard drill chuck and are selected alongside drill bits for large-diameter work.

Pilot / combination bits: Combined pilot-drill and countersink in a single tool, with a depth stop collar. The standard tool for production screw-fixing in timber. Available in sizes matched to common screw gauges (No. 6, No. 8, No. 10 etc).

Allen key / hex driver bits: Not drill bits — these are driver bits for hex socket fasteners. A common source of confusion when purchasing. They fit in a standard 1/4" hex bit holder but do not cut material. If you are searching for "allen key drill bit" you are most likely looking for a hex driver bit.

Annular cutters: Used in magnetic base drills for precision large-diameter holes in structural steel. Produce a clean, burr-free hole without the full core being cut away. Not handheld drill bits — specific to mag drill use.

End mills (a separate tool family): Often confused with drill bits because they look similar in a chuck, but end mills are sideways-cutting milling tools — not drill bits. They cut on the periphery as well as the end, are designed for milling rather than drilling, and most cannot plunge straight down without a centre-cutting design. For full coverage of types, flute count, coatings and selection see our End Mill Guide.

Material selection quick-reference

Use this table when you need a fast answer. See the relevant section above for technique, speed and cutting fluid detail.

When to sharpen a drill bit and when to replace it

"Drill bit sharpener" generates 1,500 searches per month in Australia — which tells you how commonly bits are run past their useful life and how often people are trying to recover them. Knowing when sharpening makes sense versus when it does not saves time and money.

Signs a bit needs attention: The bit requires noticeably more pressure than it used to. It produces a squealing noise in metal rather than a steady cutting sound. You can see smoke or a burning smell in timber. The entry wanders despite centre-punching. These are all signs the cutting edge has rounded or chipped.

When sharpening is worthwhile: Larger HSS twist bits (10 mm and above) are worth sharpening. The geometry can be restored accurately with a bench grinder using a drill bit sharpening jig, or with a dedicated benchtop bit sharpener. Cobalt bits are always worth sharpening — the cobalt is through the full body, so resharpened cobalt remains cobalt. Keep the point angle consistent (118° or 135° to match the original geometry) and maintain the clearance angle behind the cutting edge.

When to replace instead: Coated bits (TiN, TiAlN, black oxide) lose their coating on resharpening. If the coating was the reason you bought them, you are better off replacing them. Small bits below 6 mm are difficult to sharpen accurately and inexpensive to replace. Carbide-tipped masonry bits are not practically resharpened at trade level — the carbide tip requires diamond grinding equipment. Replace them. Spade bits, brad-point bits and Forstner bits can be sharpened with a file or dedicated sharpener if you know the geometry, but for most trade applications, replacement is faster.

Storage: Loose bits rolling around a toolbox is the single fastest way to blunt sharp drill bits. Index cases, individual plastic tubes, or a foam-lined roll are all better options than a loose pile. Bits stored touching each other chip each other's cutting edges through vibration alone.

Drill bit shank and chuck compatibility — the quick check

Before buying bits, confirm the shank type matches your drill. The most common incompatibility is SDS-plus bits in a standard keyless chuck — the shank will not seat or grip correctly. The second most common is 1/4" hex shank impact-driver bits in a smooth-jaw chuck — they will typically seat and turn, but round shank bits grip more securely in a standard chuck.

Standard round shank: Compatible with all keyed and keyless chucks. The universal default.

1/4" hex shank: Designed for quick-release hex bit holders and impact drivers. Will seat in a standard chuck but not preferred for larger diameters where torque transfer matters.

SDS-plus: Requires SDS-plus chuck only. Not compatible with standard drills without an adaptor (adaptors compromise hammer performance).

SDS-max: Requires SDS-max chuck only. Not compatible with SDS-plus without adaptor.

Once you have matched the shank type to your drill, check the maximum bit diameter your drill is rated for. Most 13 mm keyless chuck drills handle HSS bits to 13 mm. Rotary hammers are rated by their SDS-plus capacity, typically 4–26 mm for standard tools and up to 52 mm for larger SDS-max machines.

Frequently asked questions

What is the difference between HSS and cobalt drill bits?

Both are high-speed steel twist bits, but cobalt bits have cobalt alloyed into the steel at 5% (M35) or 8% (M42). The cobalt increases the bit's red hardness — the ability to hold a cutting edge at elevated temperatures — to approximately 650 °C, compared to ~600 °C for standard M2 HSS. Cobalt bits are harder and more heat-resistant, making them the correct choice for stainless steel, hardened steel and high-tensile fasteners where standard HSS bits glaze and blunt quickly. For mild steel, aluminium and timber, standard HSS performs well at lower cost. Cobalt bits can be resharpened without losing their properties, because the cobalt is throughout the steel, not in a surface coating.

Can I use a metal drill bit on wood?

Yes. Standard HSS twist bits cut timber without damaging the bit. The hole quality will be adequate for most rough carpentry applications — framing, rough cable runs, general construction. Where they fall short is in clean entry and exit holes: a standard twist bit tends to wander slightly on entry to timber and produces some tear-out on exit. For joinery, furniture and any work where the hole edge is visible or dimensionally critical, a brad-point (lip-and-spur) bit produces a cleaner result. In practice, most trades carry both — HSS twist bits for general cutting and brad-point bits for timber work where finish matters.

Can I use a wood drill bit on metal?

No — at least, not effectively. Brad-point bits have a soft-steel centre spur that will immediately deflect on metal. Spade and auger bits are made from carbon steel without the hardness required for metal cutting. Forstner bits will be ruined on the first contact with metal. For occasional accidental mis-use the damage may be limited to blunting the bit, but deliberate use of timber-specific bits in metal is not workable. Use HSS or cobalt for metal.

What drill bit do I use for concrete or brick?

Carbide-tipped masonry bits for standard brick, mortar and render. Use with hammer mode on a standard drill for holes up to approximately 8 mm in standard clay brick. For holes larger than 8–10 mm, or for drilling into concrete or dense block, use an SDS-plus masonry bit in a dedicated rotary hammer drill. The independent hammer action of an SDS rotary hammer is significantly more effective than the hammer mode of a standard drill for harder masonry. Never use masonry bits on ceramic tile.

Do I need a hammer drill for masonry drill bits?

Not always, but it helps significantly above small diameters. Masonry bits will rotate without hammer action, but the percussive impact fractures the masonry material much faster than rotation alone. For small pilot holes (4–6 mm) in soft brick, rotation-only may be adequate. For anything larger, or in concrete and hard block, hammer mode on a standard drill or a dedicated SDS rotary hammer is the correct approach. Using a standard drill without hammer mode on dense concrete is extremely slow and risks overheating the drill motor.

What does the colour of a drill bit tell you?

The colour indicates the surface coating or treatment — it does not tell you what material the bit cuts. Black = black oxide treatment on HSS (not a wood-specific bit). Gold = TiN (titanium nitride) coating on HSS — a minor hardness improvement that is lost on resharpening. Silver/bright = uncoated HSS or masonry carbide tip. The common belief that black bits are for wood, gold for everything, and red tips for concrete is incorrect. Identify the correct bit by its tip geometry and material specification, not its colour.

Is a titanium drill bit actually better than HSS?

Marginally, and temporarily. TiN (titanium nitride) coating adds approximately 3–5 micrometres of harder material to the surface of an HSS bit. This provides a slight improvement in surface hardness and lubricity, which can extend bit life in general metalwork. However, the coating is entirely removed when the bit is resharpened, permanently eliminating the benefit. For high-volume metalwork where bits are regularly resharpened, cobalt HSS is a significantly better investment — the cobalt is in the steel throughout the bit, not in a removable coating. For occasional use, TiN-coated bits are a reasonable choice at modest cost premium over uncoated HSS.

What drill bit should I use for stainless steel?

Cobalt HSS, grade M35 minimum. Standard HSS bits will work-harden the surface of 304 or 316 stainless steel almost immediately, creating a zone harder than the bit itself. Cobalt bits maintain their cutting edge at the higher temperatures generated by stainless. Technique is equally important: slow speed (approximately 60–80 RPM for holes 6 mm and above), firm continuous feed pressure, cutting fluid applied before starting, and no stopping mid-cut. Stainless steel work-hardens under interrupted cutting — if you pause and restart, the rehardened entry zone will blunt or stop the bit. Drill through in a single continuous pass where possible.

What drill bit do I use for ceramic or porcelain tiles?

For glazed ceramic wall tiles, a carbide spear-point bit works at low speed with no hammer action. For porcelain floor tiles (significantly harder than ceramic), a diamond-coated bit with continuous water cooling is required. Porcelain has a hardness of approximately 6–7 on the Mohs scale — harder than most ceramics and aggressive on carbide-only bits. In all tile drilling: no hammer mode, low speed, do not apply excessive downward pressure, and keep the bit wet for diamond bits. Starting the hole at an angle to the surface, then correcting to 90°, helps prevent the bit from skating before it bites.

What drill bit should I use for rendered brick?

A standard carbide-tipped masonry bit is sufficient for drilling through render. Render is a sand-and-cement mix that is softer than the substrate beneath. The decision point is what lies under the render: if it is standard clay brick, a carbide masonry bit with hammer mode on a regular drill handles the full depth. If it is dense concrete block, switch to an SDS-plus masonry bit in a rotary hammer for the block portion. If you are unsure, drill slowly through the render layer and assess the resistance as you reach the substrate. Increased resistance and slower progress typically indicates concrete block.

What is the difference between SDS and SDS-plus drill bits?

In Australian trade usage, "SDS" almost always refers to SDS-plus — the 10 mm shank standard used in the overwhelming majority of rotary hammers from 2–8 kg. The original SDS specification was superseded by SDS-plus, which is now the standard system for this size range. SDS-max is a larger and heavier system (18 mm shank) used in heavy demolition and large core drilling. SDS-plus and SDS-max bits and chucks are not directly interchangeable. A small number of older tools use the original SDS or a proprietary system — check your drill's manual if unsure.

What point angle should a drill bit have — 118° or 135°?

Standard general-purpose twist bits to DIN 338 use a 118° point angle. For hard metals, sheet metal and precision work, a 135° split-point (web-thinned) bit is preferred — it is self-centring, requires less starting pressure and is less likely to walk on a smooth surface. For timber and general workshop use, 118° is the standard. If you are buying a single set for mixed use, 135° split-point HSS bits are a good choice as they perform well across metals, plastics and timber without requiring a centre-punch on smooth surfaces.

How do I know when a drill bit needs replacing or resharpening?

The clearest signs are: noticeably more pressure required to advance the bit; squealing or screaming in metal instead of a steady cutting sound; smoke or burning smell in timber; the bit wandering on entry despite a centre punch; or a blue/straw discolouration on the tip (heat damage from running too fast or too dry). For HSS and cobalt bits 10 mm and above, sharpening restores performance. For coated bits (TiN, black oxide), resharpening removes the coating — replacement is usually more cost-effective. For carbide masonry bits and small bits below 6 mm, replace rather than sharpen.

Browse drill bits at AIMS Industrial: We stock HSS twist bit sets, cobalt drill bits for stainless and hard metals, carbide-tipped masonry bits, SDS-plus bits, step drill bits, countersink sets and hole saws — all available for same-day despatch from our Milperra warehouse. View the full drill bit range.

Related guides: Drill Bit Size Chart: Metric, Imperial & Fractional | Step Drill Bit Guide | Tap & Die Guide: Cutting Threads in Metal | Choosing the Right Drill Bit

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