Which end mill geometry for which job
These five geometries cover most milling work. Each trades rigidity, chip room or surface finish against the others.
| Geometry | Best for | Trade-off |
|---|---|---|
| Square | Shouldering, slots, general profiling | The sharp corner is the weak point and chips under load |
| Corner radius | Profiling where corner strength matters | Cannot produce a true square internal corner |
| Ball nose | 3D contouring, moulds and dies, finishing curved surfaces | Cutting speed falls to zero at the centre, so feed must be reduced |
| High feed | Roughing at high table feed with shallow depth of cut | Suits shallow axial depth only; not a general-purpose cutter |
| Roughing with chip breaker | Heavy stock removal in steel | Leaves a rougher finish and needs a finishing pass |
Helix angle and chatter
The helix angle controls how the cutting force is directed. A low helix of about 30 degrees suits harder materials and heavy roughing, where the priority is edge strength. A high helix of 45 to 50 degrees shears the material more cleanly and improves finish in softer steels and aluminium, but it directs more force upward, which pulls the tool out of the holder and demands a rigid setup.
Variable helix and variable index designs break the regularity of the cutting impulse, which is what causes resonance. On a long-reach operation or a thin-walled part they are frequently the difference between a stable cut and chatter that ruins the surface.
Runout: the number that decides tool life
Runout is the measurement most often ignored and most directly linked to tool failure. A cutter running out of true loads one flute harder than the others, so that flute wears or chips first while the rest still have life left.
We hold 0.005 mm TIR on solid carbide end mills, but assembled runout at the machine also depends on the holder and the collet. Supplying tool, holder and collet together lets us state the runout of the assembly rather than of the tool alone.
Coatings for milling
- AlTiN for hard milling and dry cutting, where the edge runs hot
- AlCrN for hardened steel and high-temperature alloys, with strong oxidation resistance
- TiAlN as the general-purpose choice for steel and stainless under coolant
- DLC or uncoated polished for aluminium, copper and composites, where a slick surface prevents built-up edge
- TiCN for cast iron and interrupted cuts, where toughness matters more than hot hardness
Frequently asked questions
What runout do you hold on end mills?
0.005 mm TIR on solid carbide end mills, measured at the cutting edge. Assembled runout in the machine also depends on the holder and collet, which is why we supply those together and can quote the runout of the set.
When should I use a high-feed mill instead of a conventional end mill?
For roughing at high table feed with a shallow axial depth of cut. The geometry directs cutting force in a favourable direction, allowing very high feed rates, but it is not a general-purpose cutter and does not replace a square or radius end mill for shouldering.
Which helix angle should I choose?
About 30 degrees for hard materials and heavy roughing where edge strength matters, and 45 to 50 degrees for softer steels and aluminium where finish and shear matter more. If chatter is the problem, a variable helix design is usually more effective than changing the angle alone.
Do you manufacture thread mills?
Yes, both solid carbide and indexable thread mills. Thread milling suits large diameters, difficult materials and blind holes, and it produces a thread by helical interpolation rather than requiring a tap of the exact pitch.
Can you reproduce a competitor's end mill geometry?
In most cases yes. Send the tool or a drawing and we will match the geometry, then recommend a substrate and coating for your material and machine. Where a different geometry would serve you better we will say so and explain why.