[Doug Baker]

I am wanting to make some special reamers that will be the four straight flute style. The problem I have is knowing what the cutting facet angle and clearance angles are. I have hunted around the net to no avail and I am hoping that some subscriber may have that info to share.

Thanks,

Doug Baker

[HuFlungDung]

The facet angle is typically 45°, not that that is particularly critical. The primary clearance could be 5°. and the secondary can be whatever, just so the heel of the facet is not higher than the cutting edge

I usually just check the clearance of the end flute with a dial indicator while the reamer is in the grinder setup. Using a very sharp point indicator stylus, place it on the heel of the facet you have ground and roll the reamer over backwards, allowing the stylus tip to drop over the cutting edge of the facet. You should see a steady incline to the ramp until the edge is reached. I would allow about .005" rise in 1/16" of rotation.

Take into account that you will be grinding the heel of the facet away for secondary clearance, so it is really the last 1/16" before the cutting edge is reached, where the ramp needs to be observed to meet the conditions above.