I purchased a 3/8" end mill holder from Little Machine Shop some time ago (which I've been very happy w/ btw!) and have been using that with single-ended endmills for a while. I purchased some double-ended end mills the other day, but after they arrived, discovered that they're a bit too long for my holder/spindle. I have an older-style Taig mill (non-ER16) and a 3/8" end mill won't fit up inside the spindle, so as a result I can't get the longer double-ended end mill far enough up into the holder to get the set screw to clamp down on the flat (because the other end hits the internal taper of the spindle before it can get far enough up in there).

I can get the end mill far enough up inside the holder to get a good solid hold on it in the holder, and can clamp the set screw down against the round part of the shank. I have successfully done a test cut on steel with it, but just want to be sure that this isn't a "bad idea" in some manner or another. Worst case I can envision is trying to take too big of a bite and having the end mill perhaps spin in the holder (since the set screw isn't on the flat), but am hoping that those wiser than me in my noob-ness can give me the 'yea' or 'nay' on this. (Oh, also, because of the extra length, I have to cut with my Z-axis higher than normal, but still have several inches over my table/vise, so its very useable from a z-axis perspective - but I suspect that this extra z height though could allow some extra machine flex that wouldn't be there at a lower z height...)

Thanks!

I'd say that since you've tested these and they work okay, just keep on going. If the endmills are high speed steel, you could grind a small flat in the appropriate spot for the set screw. This would eliminate the possibility of them spinning in the holder and taking out both the holder and endmill.

This might not be the best combination, but you've proved that it works. Just follow your instincts and stay away from the really heavy cuts.

Glenn

you may want to watch for the bit working its way down also. I have had it happen a few times without weldon shank tooling. Never had one come out or spin but have had it increase the depth of cut along the axis. Without flats I almost always use a collet now. but you can do like Glenn said and grind a small flat onto it or even mill a flat onto it with a carbide mill if its hss. Just my two pennys though.