Why small tools break
Below about 2 mm diameter, the tool shank is slender enough that runout at the holder translates almost directly into a bending load at the cutting edge. A holder that is entirely adequate for a 10 mm cutter will break 1 mm tools repeatedly.
The other common cause is a feed rate applied from a larger-tool habit. Small tools need a feed per tooth matched to their size, and running a 1 mm cutter at a 10 mm cutter's feed is an instant breakage.
- Check runout at the tool, not at the holder
- Use a precision collet or shrink-fit holder matched to the small shank
- Reduce feed per tooth with diameter; do not scale it from a larger tool
- Use a spot or pilot operation so the tool does not walk on entry
- Keep the tool as short as the feature allows to reduce overhang
Materials and what they demand
Medical work concentrates on stainless steels, titanium, cobalt chrome and, for instruments, hardened stainless.
| Material | Challenge | Tooling direction |
|---|---|---|
| 316L and 17-4PH stainless | Work hardening, galling | Sharp PVD-coated edge, firm feed, no dwelling |
| Titanium grade 5 and 23 | Heat at the edge, spring-back | Sharp AlTiN edge, low speed, generous coolant |
| Cobalt chrome | Abrasion and work hardening | AlCrN or AlTiN, strong edge, conservative speed |
| Hardened instrument stainless | Abrasion | AlCrN hard milling or grinding where hardness exceeds 50 HRC |
Surface finish as a functional requirement
On an instrument or an implant surface, finish is not cosmetic. A surface that is too rough traps contaminants and resists cleaning; a surface that is over-polished can lose the texture needed for a coating or a bond to key into.
Achieving a specified finish comes from the combination of tool geometry, edge condition and the finishing parameters, not from a separate polishing operation. A worn tool will not produce a specified finish no matter how the parameters are adjusted, which makes finish a tool-life indicator as much as a quality characteristic.
Cleanliness and documentation
Burrs on a medical component are a functional defect rather than a cosmetic one, and a loose chip inside a device is a field failure. Tooling that produces a clean exit burr reduces the deburring burden, and through-coolant delivery helps clear chips from small features.
Where the finished device is regulated, the tool batch records form part of the traceability chain. We supply material and coating certificates and dimensional records, and can serialise records where your quality system requires it.
Frequently asked questions
What is the smallest tool you manufacture?
0.5 mm in solid carbide micro drill geometry, and small end mills from the same size. Below that, runout at the holder dominates the result, so we supply matched precision collets and holders alongside the tool.
Why do my small tools keep breaking?
Almost always runout at the holder or a feed rate scaled from a larger tool. Check runout measured at the cutting edge rather than at the holder, use a precision or shrink-fit holder, and set feed per tooth from the tool diameter rather than from habit.
Which coating for machining 17-4PH stainless?
A sharp PVD coating such as TiAlN or AlCrN with a fine edge preparation, run at a firm feed. The objective is to cut rather than rub, because dwelling on the surface work-hardens it and makes the next pass harder than the last.
Can you help achieve a specified surface finish?
Yes. Tell us the required Ra and the feature, and we will propose a geometry and edge condition to produce it. Finish is largely set by the tool rather than the parameters, so a correct tool removes the need for a separate polishing operation.
Do you supply tools for implant manufacturing?
We supply tooling to machine implant materials, but we are not a medical device manufacturer and do not claim a validated medical manufacturing environment. Any regulatory requirement on your process needs to be stated at quoting so we can say whether we can support it.