Collet vs holder run out

As you move to smaller end mills, runout matters a LOT more. 0.001" for a 1/2" end mill is no big deal, but is enough to snap a 1/8" carbide end mill. So anything under 1/4" I mount in an ER32 R8 collet chuck and tap in the cutter to lower the runout to near zero. Watch this video starting at 10:35 in the timeline:
 
davidpbest said:
As you move to smaller end mills, runout matters a LOT more. 0.001" for a 1/2" end mill is no big deal, but is enough to snap a 1/8" carbide end mill. So anything under 1/4" I mount in an ER32 R8 collet chuck and tap in the cutter to lower the runout to near zero. Watch this video starting at 10:35 in the timeline:
Click to expand...
I watched that video three hours ago. I have been doing that when holding work in an er40 collet chuck for a few years. I hadn't though about it with a cutting tool.

I'm more interested in the practical accuracy of an end mill holder vs r8 collet
 
davidpbest said:
Then watch this:
Click to expand...

Saw that one too. I'm not using the Tormach system. If that is the one where he chucked the holder up in the lathe his methodology was terrible. He should have dialed in the holder in two places.
 
Batmanacw said:
Saw that one too. I'm not using the Tormach system. If that is the one where he chucked the holder up in the lathe his methodology was terrible. He should have dialed in the holder in two places.
Click to expand...
OK, I'll shut up now. Happy New Year.
 
davidpbest said:
Then watch this:
Click to expand...
The surface of the end mill holder that John is using for a mount isn't intended to be a precision surface. Certainly, the addition of the tape doesn't help. While John Adjusts for zero runout inside the bore of the end mill holder, if there is a cant to the mounting, there will be angular runout and a measurement outside the bore will show TIR. To determine this, he should have checked at different distances from the end mill holder.
 
RJSakowski said:
The surface of the end mill holder that John is using for a mount isn't intended to be a precision surface. Certainly, the addition of the tape doesn't help. While John Adjusts for zero runout inside the bore of the end mill holder, if there is a cant to the mounting, there will be angular runout and a measurement outside the bore will show TIR. To determine this, he should have checked at different distances from the end mill holder.
Click to expand...
If he dialed it in two spots in the bore it would have worked fine.
 
That is true assuming he can actually zero runout at two places in the bore.
 
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