End Mill Configuration

[runner42]

I have broken 5 small end mills in cutting a slot in steel, each time the failure point was at the junction of the shank and the cutting end of the end mill. This was using Chinese end mills with small cuts and slow feed rates. The configuration of these were the shank was a larger diameter than the cutting diameter so in manufacture there was a stress point introduced at the junction so they easily broke. With this in mind I obtained end mills where the shank diameter is the same as the cutting diameter and still Chinese they can be more robustly used without breaking. This type of configuration appears to be peculiar to small end mills and I assume to make the shank diameter larger is to reduce the range of Collets used. I share my experience should anyone obtaining small end mills suffer the same mishap.

Brian


       

[uuu]

I rather prefer the end mills with a wider shank. I have broken some of the plain ones (usually my fault - clumsy programming), and they go right up at the collet. In some cases a small bite has been taken out of the collet. It might also be that the wide-shank ones are a bit stronger as there's less leverage at the possible break point.

I'm happier buying more cutters and fewer collets.

Wilf