Learned a lot today

[rock_breaker]

Apparently I successfully sharpened a 4 flute end mill today. The sharpening was done on a Enco Tool and Cutter sharpener that came from an estate sale. The machine has multiple adjustment capabilities as the shaft holding a grinding stones on each end can be rotated horizontally and vertically. With the motor mounted on the spindle frame it can be raised and lowered vertically as well. Two tailstock assemblies were among the accessories: one is an indexing R-8 tool holder that held the subject 1/2" 4 flute HSS double end mill. An attempt at sharpening was made earlier but the mill did not perform well. This time after re-reading Harold Hall's" book again, the center was ground prior to grinding each flute at approximately 15` to develop a concave center and the relief angle was 15` also.
The end mill was tested by trueing up the adjustable plunger bar for a rotary indexer that I am trying to make utilizing a 40 to 1 worm gear that was surplussed by the cement plant I retired from. The bar came out smooth and true.
The reliability of the end mill will determine if I did in- fact get the job done close to correctly. This has been one of the learning challenges encountered while making the indexer. There are other mills in my tool box but this was a task (skill) I need to learn.
Have a good day
Ray

 

[4GSR]

A 1/2" is a decent size to practice on. Larger ones are much easier to sharpen. 3/8" are ok anything smaller, well good luck sharpening them.

A couple of pointers I've found to help are. Make sure your finger is at the centerline of the spindle and or lower by a fraction or so. If you have a height gage handy, turn the scriber upside down so it points upward. Set it at the center of the endmill. Then move out to the flute to sharpen and adjust the finger so the leading edge of the cutting edge is even with the tip of the height gage. When that's done, go to the opposite flute and check where the cutting edge is in relation to the height gage. If its high or low, adjust the height gage at about half of that difference to new center height. Go back and adjust the finger height so the leading edge of the end mill to sharpen is at the new height of the height gage. Last re-check the back side flute, it should be the same. If not adjust again until both cutting edges are at the same height.
Once this is done, then you can adjust the angle the radial clearance for the first and second land on the cutting flutes of the endmill. I prefer to use the old Weldon chart, I'm sure there are others out there that are very close to the same. Sharpening the ends, I hate to do on smaller end mills, especially one's that have chipped corners. Rater than grinding all the length off to get rid of the chipped corner, I usually grind a 45 degree edge break on the corners. On grinding the ends, a 1-1/2 to 5 degrees is all you need for clearance angle on the ends. 5 degrees is plenty of clearance for the first relief cut follow by about 10-20 degrees for the secondary cut in my opinion. I usually try to match up to the existing angles when sharpening, but not always followed. I've ground face angles from about 15 to 45 degrees for specific applications, too.

Hope this helps, sounds like your getting a handle on end mill sharpening. Next thing you know, you'll be an expert!

Ken

 

[rock_breaker]

Thanks Ken, you have added things I have overlooked and I appreciate the help. I have a 4"recessed wheel for this work and a 6" wheel that I used to sharpen a 7/16" drill bit today. Surprisingly it came out about as good as I have done in about 30 years. Enco's picture of a drill grinding attachment is of a General or Craftsman swinging holder usually found beside bench grinders. The tailstock holding the R-8 tool holder is fastened on a mill table that has a coarse movement of the table, I need to master this or find an alternate feeding method.
I was once told an "expert is a guy carrying a briefcase over 50 miles from home.".
Have a good day
Ray