Sharping roughing end mills

[sizmo]

This is for the professional tool grinders. I am trying to sharpen some roughing end mills . I know you grind in the gullet . Useing a 7 inch wheel 1/4 wide dressed a radius on face .l kicked around the head to grind in the flute . The mills look and feel sharp but wont cut like they should. CANT figure out what i am doing wrong. Useing a Chevalier 610 grinder with air bearing fixture I have seen it done using a lot smaller wheel around 2 in dia never a 6 or 7 in . wheel but cant use any thing smaller .Grinder uses 1 1/4 a wheel hole size. HELP.

[HuFlungDung]

When you began the grind, I suppose you started with a very light cut to ascertain the position of the wheel? Now it is very simple to take lots off the front of the tooth face because it is 'easy going', but not so easy to get the wheel down in the gullet and remove a considerable amount of material to keep the rake face of the gullet exactly the same shape as it was before. I suspect you have decreased the positive rake of the tooth face, which makes the tool less free cutting.

Solution? I don't know if the large wheel diameter is the cause of the problem, but try another tool, and be very observant of how much you are taking off the tooth face. You might have to just change the start angle of the tool in the indexer.

I suppose if you have an optical comparator, you could slice off a section through an original tool, and a resharpened one, to compare the exact contour you have achieved.

[Donald]

Sizmo,
I've always used a saucer stone wheel for grinding inside the flutes of roughters. And I'm not sure what sizs of tool your attempting to sharpen, but it should be between 6 - 11 degree's of rake.

I've dressed a radius on the outer diamter of the wheel that would fit the contour of the existing rake of a tool that hasn 't been ground. And make sure you spin the head that the wheel spindle is on to match the helix\spiral.
Then adjust the height of the wheel ( probably
Try to twist the tool ( held in the collet and the airbearing ) into the wheel so that you feel the diamter of the wheel in the bottom of the flute and just touching the cutting edge of the tool.
If the outside diamter of the flutes still has dull in it then lower the wheel just a few thousands ( 0.005 - 0.015 ) and twist the tool into the wheel more and repeat until all the dull is out of the tool.
If you drop the wheel to much and you will make the tool very aggressive and possible will grab and snap or break off.

Hope this helps
Don

[Willbird]

You almost need a smallish wheel, or the helix angle combined with the larger dia wheel really mess's stuff up :-)

Bill

[mc_n_g]

A shaped saucer type wheel should be used 1 to 2 degrees offset from the original helix angle to lightly remove material from the front of the cutter surface. This can be very tricky without a proper set up. Plus there is only so much you can take off before the roughing mill is useless.
It is kind of like trying to resharpen a tap. Extremely tricky to perform unles you have done it before to get the proper hook angle.