Corner Radius End Mills

AIMS Industrial stocks 25 corner radius end mills from Sutton Tools, in solid carbide and HSS, covering micro diameters from 1mm through to 20mm-plus, with corner radii from 0.1mm up to 5mm across 2, 4, 5 and 6-flute configurations. Corner radius end mills — also called bull nose end mills — have a small radius blended between the peripheral cutting edge and the flat bottom of the cutter, rather than the sharp 90-degree corner of a square end mill. That radius takes the single biggest source of stress off the most vulnerable point of the tool, which is why it's the default choice for roughing hardened steel, dies, moulds and anything where a square end mill tends to chip out at the corner. For a deeper dive on the standards and selection criteria, see our Carbide vs HSS End Mill: When to Upgrade.

Every corner radius end mill on this page is genuine Sutton Tools stock, held in our Sydney warehouse for same-day dispatch on in-stock lines. If you're not sure which radius, flute count or coating suits your job, call our team on (02) 9773 0122 or send us the material and application through Request a Quote — we'll match it to the right part number.

Quick Reference — Corner Radius End Mills at AIMS

Corner Radius vs Square, Ball Nose and Corner Chamfer End Mills

A standard square end mill cuts a sharp 90-degree internal corner but that sharp edge is also the weakest point of the tool — it's the first place a cutter chips under load, especially in hardened steel, stainless or titanium. A corner radius end mill blends a small radius into that corner instead, spreading the cutting stress over a curve rather than concentrating it at a single point. The result is a stronger edge that holds up far better under roughing loads and abrasive or hardened material.

It's worth being clear on where a corner radius end mill sits relative to its relatives, because the terms get mixed up constantly on the shop floor:

• Corner radius (bull nose) end mill — flat across the bottom, with a small radius blended in at the corner only. Cuts a flat floor with a filleted wall-to-floor transition.
• Ball nose end mill — the entire bottom of the cutter is a full hemispherical radius, with no flat area at all. Used for 3D contouring and curved surfaces, not flat-floor work. See our Ball Nose End Mills range.
• Corner chamfer end mill — an angled flat (not a radius) at the corner, typically used for deburring and chamfering edges rather than tool-life protection. See Corner Chamfer End Mills.
• Square end mill — sharp 90-degree corner, used where a true sharp internal corner is required by the part design. See Square End Mills.

If your part needs a flat floor with a small fillet where it meets the wall — or you're roughing tough material and don't want to keep replacing chipped square end mills — a corner radius end mill is the right call.

Choosing Flute Count

Flute count trades off chip clearance against edge strength and finish. Across this range Sutton stock corner radius end mills in 2, 4, 5 and 6-flute configurations:

• 2-flute — the most chip clearance of the range, suited to slotting and softer or gummier material where evacuating swarf matters more than edge count. Stocked in the micro end mill line down to 1mm diameter.
• 4-flute — the general-purpose choice across most of this range, balancing chip clearance with edge strength for steel, alloy and general workshop milling.
• 5-flute — less chip room but more cutting edges engaged at once, giving a smoother finish and higher metal removal rate in steel — the AlNova, Xceed and Alnova HA/HB ranges here are 5-flute.
• 6-flute — the most edges in the range, for finishing passes and high-feed work in steel where surface finish and edge life matter more than raw chip clearance.

As a rule: more flutes suits harder material and finishing operations where you want more cutting edges sharing the load; fewer flutes suits softer material and roughing operations where chip evacuation is the limiting factor.

Choosing a Coating

Every carbide corner radius end mill in this range carries a PVD coating matched to the job it's built for:

• TiAlN — the general-purpose coating in this range, giving solid heat resistance for everyday steel and alloy milling.
• AlCrN — Sutton's "Ultra AlCrN" line, rated for higher cutting temperatures than TiAlN, so it's the pick for hardened steel and tougher alloys where heat build-up is the limiting factor on tool life.
• TiSiN — used on the micro-diameter end mills in this range, where a very hard coating helps a small-diameter tool survive high-RPM, light-chip-load cutting.

If you're not sure which coating suits your material and you'd rather not guess, get in touch and we'll talk you through it against the job.

Sizing — Diameter and Corner Radius

Corner radius end mills in this range are specified by cutting diameter and corner radius together — for example a 1mm diameter with a 0.1mm radius at the micro end, up to 20mm diameter with radii to 5mm in the larger AlNova and Xceed ranges. Diameters run from 1mm micro tooling through to 20mm-plus metric sizes, plus imperial sizes from 3/16" up to 1" in selected lines. Corner radii commonly stocked include 0.1, 0.2, 0.3, 0.5, 1, 1.5, 2, 2.5, 3 and 4mm, varying by product line and diameter — check each product page for the exact radius options available on that model.

As a starting point: if the drawing doesn't specify a radius, a small radius (0.1mm to 0.5mm) delivers most of the tool-life benefit with minimal effect on floor and wall geometry. Where the design calls for a larger fillet — common in die and mould cavities — match the radius to the print rather than defaulting small. The radius can't exceed roughly half the cutter's diameter, so smaller-diameter tools are limited to smaller radii regardless of what's technically available in the range.

Solid Carbide vs HSS

Most of this range is solid carbide (VHM), which runs faster, holds an edge longer and handles harder material than HSS — the right default for CNC machining centres and most modern milling work. AIMS also stocks corner radius end mills in HSS slot drill & endmill format, a lower-cost option that suits manual milling machines, lower-volume work, or jobs where the extra cost of carbide isn't justified by the run length. If you're running a CNC and pushing higher feeds and speeds, carbide is almost always the better economic choice despite the higher unit price — it just gets there through tool life rather than sticker price.

Applications

Corner radius end mills from this range are used for peripheral and slot milling in hardened and difficult-to-machine steels, contour and profile milling where a filleted corner is required, semi-finish and finish milling of 3D profiles in dies and moulds, and general roughing where corner chipping on a square end mill is costing tool life. They're common in toolroom, mould-and-die, and general precision engineering work across Australian machine shops, fabricators and maintenance workshops running CNC machining centres or manual mills.

Brand Stocked

Every corner radius end mill in this collection is genuine Sutton Tools — an Australian-owned cutting tool manufacturer AIMS has stocked for years. We don't mix in grey-market or unbranded alternatives on this range; what you see on the product page is what ships.

Companion Ranges

Corner radius end mills are usually one part of a broader milling cutter kit. These AIMS ranges cover the rest of it:

• End Mills & Milling Cutters — the full milling cutter range across all corner styles
• Square End Mills — sharp-corner end mills for true internal corners
• Ball Nose End Mills — full-radius cutters for 3D contouring
• Corner Chamfer End Mills — angled-corner end mills for deburring and chamfering
• Slot Drills — for direct plunge and slotting work
• Carbide Drill Bits — for hole-making alongside your milling operation

Order From AIMS

All 25 lines in this range are genuine Sutton Tools stock, held ready to ship from our Sydney warehouse. If you need help matching a diameter, radius, flute count or coating to your job — or you're after a quantity price — call our team on (02) 9773 0122, reach out through Contact Us, or send your requirements through Request a Quote and we'll get back to you with the right part number and pricing.

Frequently Asked Questions

What is a corner radius end mill used for?

A corner radius end mill is used wherever a square end mill's sharp corner would chip or wear out too fast — hardened steel, tough alloys, and aggressive roughing operations. The small radius at the corner spreads cutting stress over a curve instead of a single sharp point, which dramatically extends tool life in demanding material. It's also used where the part design calls for a small fillet where a wall meets a floor.

Is a bull nose end mill the same as a corner radius end mill?

Yes — bull nose end mill and corner radius end mill describe the same tool: a flat-bottomed cutter with a small radius blended into the corner rather than a sharp edge. "Bull nose" is the more common shop-floor term; "corner radius" is the more precise engineering description. Both terms are used interchangeably across the trade and by tooling manufacturers.

What's the difference between a corner radius end mill and a ball nose end mill?

A corner radius (bull nose) end mill is flat across the bottom with only the corner radiused, so it cuts a flat floor. A ball nose end mill has a full hemispherical radius across the entire bottom, with no flat area at all, and is used for 3D contouring and curved surfaces rather than flat-floor work. If your job needs a flat floor, use a corner radius end mill; if it needs a curved 3D surface, use a ball nose end mill.

What flute count should I use for a corner radius end mill?

It depends on the material and operation. Fewer flutes (2) give the most chip clearance and suit slotting or softer material; 4-flute is the general-purpose choice for steel and alloy work; 5 and 6-flute tools carry more cutting edges for better finish and higher metal removal rates in steel, at the cost of chip clearance. As a rule, go with more flutes for finishing and harder material, fewer flutes for roughing and chip-heavy operations.

Which coating should I choose — TiAlN, AlCrN or TiSiN?

TiAlN is the general-purpose coating for everyday steel and alloy milling. AlCrN (Sutton's "Ultra AlCrN" line) handles higher cutting temperatures, so it's the better choice for hardened steel and tougher alloys where heat is the limiting factor. TiSiN is used on the micro-diameter tools in this range, where a very hard coating helps a small tool survive high-RPM, light-chip-load cutting. If you're unsure, tell us the material and we'll recommend a coating.

What corner radius sizes does AIMS stock?

Corner radii across this range commonly run from 0.1mm up to 5mm, varying by product line and diameter — the smallest radii (0.1–0.3mm) are on the micro end mill lines, while larger radii (1mm and above) are available on the bigger diameter ranges. Check the variant options on each product page for the exact radii stocked for that model.

What diameters are available?

This range runs from 1mm micro-diameter end mills through to 20mm and above in metric sizes, plus imperial diameters from 3/16" to 1" on selected lines. Diameter and corner radius are specified together, so the radius options available depend on which diameter you select.

Should I use solid carbide or HSS?

Solid carbide runs faster, holds an edge longer and handles harder material — it's the right default for CNC machining centres and most current milling work, and it's what most of this range is stocked in. HSS costs less up front and suits manual milling machines or lower-volume jobs where carbide's extra cost isn't justified by the run length. If you're on a CNC pushing real feeds and speeds, carbide almost always wins on cost-per-part despite the higher unit price.

Can a corner radius end mill cut a slot like a square end mill?

Yes — corner radius end mills handle general slotting and profiling the same way a square end mill does, except the finished floor-to-wall transition carries a small fillet instead of a sharp corner. If your part needs a true sharp internal corner, use a square end mill instead, or finish the corner with a separate operation.

Can corner radius end mills be resharpened?

Yes, but it's a more specialised job than resharpening a square end mill — the radius profile has to be maintained accurately through the regrind, which needs CNC tool grinding equipment set up for radius profiles. Most workshops send corner radius tooling to a specialist regrind service rather than attempting it in-house.

What's the minimum order or do you sell single end mills?

We sell individual end mills as well as bulk quantities — there's no minimum order to buy a single corner radius end mill from this range. For larger or recurring quantities, get in touch through Request a Quote and we'll put together a price that reflects the volume.

How quickly can AIMS supply corner radius end mills?

In-stock lines from this range ship same day from our Sydney warehouse. If a specific diameter, radius or flute combination isn't showing as in stock, call us on (02) 9773 0122 and we'll confirm lead time before you order.