Amateur Machinists' Tools, Techniques and Materials

Archive for November, 2013

Drill Doctor

Posted by hammerscale on November 22, 2013

I’ve owned a Drill Doctor for a while and find it quite an asset to the shop. Recently, after sharpening a fairly large diameter bit with the DD I found it rubbing instead of cutting. I recognized this immediately as negative relief. In other words, the cutting edge, though sharp, was lower than the following edge. I had never had this issue grinding small bits, and a few attempts at fiddling with the DD settings proved fruitless. As much as I hate to admit it, I had misplaced the user guide, so off to the www.

My search brought me to the following video;


This addressed directly the issue at hand, and the girl with the French manicure pointed me towards the solution.  First, I followed the directions to grind completely (spark out) which seemed to help, but only minutely. I then adjusted for greater relief as instructed, choosing the maximum setting.  After grinding, the bit was just beginning to cut, and I could see some small chips lifting off, but the bit still rubbed when pushed.

As I had adjusted the bit’s maximum relief in the DD chuck, the third attempt I set using ” seat of my pants” adjustment. I rotated the bit manually just a small amount further in the chuck, maybe 1/8 of a turn.  This did the trick, as after grinding the drill bit cut thru steel like butter.

This adds a little trial and error for setting up a bit in the DD, just something to be aware of.

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