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Sharpening multi flute endmills

Peter Colman

Stainless
Joined
Sep 22, 2004
Location
Rugeley UK
I normally sharpen the end of 4 flute endmills using one of those attachments that takes a 5c collet and has an angled base to sit on the mag table of my surface grinder.
This is fine until I try to sharpen a cutter with 6 flutes, I end up damaging the adjacent flutes. Have I missed a trick or am I being stupid?
Peter
 
I have not used that method for a long time, so my memory may be hazy. I recall making an attachment for my B&S No. 2 surface grinder that locked the longitudinal table travel and included a fine adjustment device. The trick for doing a 6-flute was to position the edge to be ground under the center of the wheel so that the cutting edge got hollow ground at an appropriate angle and the wheel did not touch the adjacent edges. Use the downfeed to grind the new edge and use the cross feed to bring the fixture toward you and away from the end mill. Then index to the next edge and repeat.

Larry
 
Larry
I have tried that, but you need a very small wheel to not damage adjacent teeth in the centre where the cutting edges meet.
Even if you use a conventional tool and cutter grinder (like a Clarkson) I can't see how to overcome the problem
 
I'm sure there's a better way, but I have used that type of fixture and just sharpened on the end as much as I could get without hitting the adjacent tooth and then relieved the whole center by hand with a Dremel/stone. The ends are sharpened concave so only the outside part cuts anyways... works fine and that's the important part.

Ted
 
At work once,I was told to sharpen up some endmills on Elliott t/c grinder. Took me most day to do a few cutters! It's definitely a special knack to it. A cup wheel seems to be favourite for something like the Clarkson. I'll have to try mine out one day,when I have a wheel for it!
 
I've sharpened them using a spin fixture, a sine plate, and using the side of the wheel. It takes some playing around to get it right, and using the side of the wheel will tend to burn more.
 
If I had to Surface grind end-mills I would set a spin index on the chuck at 5 to 10*off 90* depending if the end mill was to be a plunge cutting on conventional cutter in the direction to give clearance (but end to the right), set perhaps a .030 shim under the away/far end of the spin index base so giving some dish, set my tooth to be ground in a vertical position, set some block -ins ahead of the spin index so it would not go flying, lock the table position so the arc of a dished wheel would arc near the cutter across center. Use a mirror to be able to se the end of the cutter, then grind with the same method as would be used on a TC grinder. The secondary I would put on by hand on a bench grinder dressed to about 20* andle.

To get the flutes to the same height I would first V block hold the end mill and flat grind the end, then with the spin index grind watch to see the flat land just be ground away.

Common to worry about side wheel grinding so I try to use a 3/4 wide and use it down to 1/2 so having greater strength/ one could flip up the wheel guard face and use a cut wheel.
 
I use a dish wheel with...I dunno, maybe a 45 degree included angle and diamond on both faces. I actually sneak in with the back side of the wheel to grind the flutes sharp. The vertical part of the wheel attends to the face of the tooth (well actually stay slightly away), but I can actually gash in with this wheel and create the new chip space after shortening the endmill. I just do this by hand, but it could be done with more care on a cutter grinder. I'm typically doing this just for a roughing cutter, so I'm not real paranoid about getting all the flutes equal. Hell, I call it a variable relieved endmill, and it's worth extra :D
 








 
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