How to choose end-mill
Choosing a solid carbide end mill starts with the job, not the catalogue: what material you are cutting, what feature you are making, and how far the tool has to reach. Once those three are clear, the series, diameter, flute count, profile and length follow almost by elimination. This is the order we work through when a customer asks us to pick one — and the order in which our solid carbide end mills for metal are sorted.
1. Series: Match the Tool to the Material
No end mill cuts everything equally well. Steel, stainless, cast iron, aluminium and titanium wear a tool in different ways, so manufacturers build series for material groups. European catalogues mark them with the ISO 513 letters and colours: P steel, M stainless, K cast iron, N non-ferrous, S heat-resistant alloys and titanium, H hardened steel.
The differences between series are rarely visible — they are in the carbide grade, the coating, the helix and the edge preparation. Two rules cover most of it:
- Steel, stainless, cast iron (P, M, K) — coated tools, usually 4 flutes or more. The coating carries the heat these materials put into the edge.
- Aluminium and non-ferrous (N) — uncoated tools with polished flutes, 2 or 3 flutes. Aluminium welds itself to a rough or coated edge; a polished flute lets the chip slide off.
An aluminium end mill in steel wears out in minutes; a steel end mill in aluminium packs its flutes and breaks. Start with the manufacturer's material recommendation — if the series is wrong, nothing else will save the tool.
2. Diameter and Shank
"End mill diameter" normally means the cutting diameter (DC). On standard sizes — 6, 8, 10, 12 mm — the shank (DCON) is the same. On intermediate and small sizes the shank is usually larger than the cutter, so the tool fits a standard holder and stays rigid.
Take the largest diameter the feature allows. A larger tool is stiffer, deflects less, chatters less and removes more material per pass. The limits are the feature — a 16 mm cutter will not make a 12 mm slot — and the machine: spindle power and torque, especially with driven tools on a lathe. Price climbs with diameter too.
The shank has to match the holder. Carbide end mills come with shanks to DIN 6535: HA is a plain cylindrical shank for collet, shrink-fit or hydraulic chucks; HB has a ground flat for the clamping screw of a Weldon holder, so the tool cannot pull out under heavy roughing.
3. Number of Flutes
More flutes mean more cutting edges per revolution — a higher feed at the same chip load and a better finish on the wall. The price is chip space: each extra flute leaves less room for the chip and needs more power and torque.
- 2 flutes — aluminium, plastics and slotting, where the chip has nowhere to go but up the flute.
- 3 flutes — the standard for aluminium: faster than 2 flutes, still enough room for the chip.
- 4 flutes — the standard for steel and stainless. Slots in steel at moderate depth; in aluminium the flutes pack.
- 5–6 flutes — side milling and finishing. Fast on a light radial step, not built for full-width slotting.
Catalogues show this with two pictograms — shoulder milling and slotting. If the slotting pictogram is missing, the tool is not meant for it.
4. Cutting Profile
- Square end — sharp 90° corner. Vertical walls, flat-bottom pockets, shoulders, slots, facing. The sharp corner is also its weak point.
- Chamfered corner — the same jobs, with a small protective chamfer on the corner. Noticeably less prone to chipping than a sharp corner.
- Corner radius — leaves a radius between wall and floor and lasts longer still, because the weakest point of the edge is gone. In steel and stainless it is usually the better default than a square tool.
- Ball nose — hemispherical tip for 3D surfaces, contours and full-radius slots.
- Chamfer mill — a pointed tool with a 60°, 90° or 120° included angle for chamfering and deburring edges along the contour.
5. Length, Reach and Neck
Within a series the standard tool has a balanced ratio of cutting diameter, flute length and overall length. Other lengths exist for specific jobs — go longer only when the part demands it, because stiffness drops fast with length.
- Short flute — enough when the full flute length is not needed; stiffer and cheaper.
- Long flute — for tall shoulders and deep walls in one pass. Less rigid and more prone to vibration; reduce the step-over or the feed.
- Long shank — when the holder or the clamping would collide with the part. The cutting part stays standard.
- Reduced neck — the body behind the cutting edge is ground below the cutting diameter, so the tool reaches deep pockets and ribs without rubbing the wall.
Whatever the length, clamp the tool as short as the part allows. Every millimetre of overhang costs rigidity.
Summary
- Series by material first — coated for steel and stainless, uncoated polished for aluminium.
- The largest diameter the feature and the machine allow, with a shank that fits your holder.
- 2–3 flutes for aluminium and slotting, 4 for steel, 5–6 for side milling and finishing.
- Corner radius or chamfered corner over a sharp one whenever the part allows it.
- The shortest tool and the shortest overhang that reach.
See our solid carbide end mills, or send us the material, the feature and the machine, and we will suggest a tool.