[SCzEngrgGroup]

I've recently bought several REALLY nice 1/2" 3-flute solid carbide endmills, but they don't have any flats on the shanks. Is it OK to use these in an endmill holder? Will they stay put under aggressive use?

Regards,
Ray L.

[Geof]

Grind a small flat on the shank of the tool. My experience is that they will not stay put under heavy cuts without this.

[SCzEngrgGroup]

Grind a small flat on the shank of the tool. My experience is that they will not stay put under heavy cuts without this.

Which raises an obvious question - Why don't they put the flats on ALL endmills? Why would you NOT want them? How are these intended to be held?

Regards,
Ray L.

[Geof]

Which raises an obvious question - Why don't they put the flats on ALL endmills? Why would you NOT want them?...
Regards,
Ray L.

You certainly do not want a flat on the shank when the tool is buzzing round at more than 10,000rpm, and even at 10,000 sometimes you can detect the unbalance as a result of grinding a flat on a cutter larger than 1/2".

[SCzEngrgGroup]

You certainly do not want a flat on the shank when the tool is buzzing round at more than 10,000rpm, and even at 10,000 sometimes you can detect the unbalance as a result of grinding a flat on a cutter larger than 1/2".

So how would these be held in a "real" CNC machine?

Regards,
Ray L.

[Geof]

Collet holders of various types and shrink fit holders. Generally when spindle speeds are very high the important points are balance and very low runout and the cutting load is not as heavy as can occur at slower spindle speeds.

[Andre' B]

Here are some examples of a higher end collet holders where you do not want any imbalance or distortion from having any kind of flat on the tool shank.
http://www.gohpi.com/HPI2007Update0807MX.pdf
http://www.albrechtchucks.com/docs/a...ing_chucks.pdf

[gus]

I grind a small flat in 3/4 carbide end mills and notice no imbalance at 12k. The diameter of the tool is much smaller than the holder thus the small material [it is really the smallest flat] is not important.

I never use collets for anything important.

I have been considering one of those hydraulic holders or milling chucks, but they are spendy