End Mill Shank Tolerance

epanzella

Active User
Registered
Joined
Apr 8, 2013
Messages
1,974
I just got a 1 inch R8 end mill holder because I have a drawer full of end mills with that shank size that I used to usein my lathe before I got a mill. They all fit the new holder but one. As (bad) luck would have it, the end mill that doesn't fit is one of my favorites. By the seat of my pants I don't think it's even a thou oversize. What's the tolerance on a one inch EM shank?
 
I don't know what the normal tolerance is, but most I have seen run from on-size to about 0.001 under. Normally a bit better than that. Maybe a bit of emery cloth would be of some help.
 
Could be a sharp edge/burr that is stopping the tool going in?
Pierre
 
I don't know either but the ones I have that I have measured were usually like around .0005" undersize, never more than .001".

Have you measured the one that doesn't fit & compared with the others?
 
Most in my meager collection run -.001 or less under size. None measure larger than -.0005 of the size. And most of mine are cheap chinese stuff. A couple are -.002 but they fit in the collet, spin with almost no runout and cut so I don't concern myself with that too much.
 
I agree with Pierre , check for a burr or sharp edge on the endmill and put it up in your lathe and stone the shank if needed . Most cutters are nominal size to -.0005 from what I've seen , but most likely there are exceptions .
 
Did you measure the shank with a micrometer? Is it possible that old favorite has a 26mm shank?
 
There are no burrs and I wired brushed it shiny in case corrosion was taking up space. I had miked it before and it was right at 1.000." I remiked it every 90 degrees this AM and it's out of round??? It's 1.0005 when the mike is lined up with the flats. I don't know how than can even happen? I guess I'll bore out a sleeve to hold the cutter end in a 4 jaw chuch and stone the shank to fit. Thanks for the help.
Ed P
 
Many bigger end mills have a center hole in the end, and non center cutting have one in both ends. They are manufactured between centers. Use that to help with your concentrically and roundness as you stone down the big end. use a nice flat stone and just barely touch it so that the high sides come down first.
 
Many bigger end mills have a center hole in the end, and non center cutting have one in both ends. They are manufactured between centers. Use that to help with your concentrically and roundness as you stone down the big end. use a nice flat stone and just barely touch it so that the high sides come down first.
Thanks for the idea. I put it on centers and stoned it in for a frog's ass fit! Took about ten minutes!
 
Back
Top