Drill Sharpening Jigs - Advice please.

John

I'm glad you think that will be helpful.

Of course its possible that your jig uses a combination of pivot angle and drill angle to get the required extra grind depth.  If I recall things correctly the angle of drill edge rotation from the vertical used by the Picador type and the pivot angle of the General type are both about 15 degrees.  I measured them a few years back but can't find the results, somewhere lost in computer space.  I guess a combination of around 7.5° each should work and has some point positional advantages relative to the grinding wheel.

Worst point is that the grind is damnably sensitive to drill point projection.  The further the point projects the greater the "cone" radius, the smaller the clearance angle and the less the geometrical increase in depth with swing angle.  It takes very little extra projection to destroy the geometry.  The standard design is barely able to cope with the small projection possible at the bottom end of the range.  Ages back I looked into creating an offset pivot position to allow a bit more projection, say 50 thou or so but decided it was  too much work for something I didn't really understand.  Plan was to fit an offset end to the pivot pin, might have done it if the pin had been screwed in rather than cast in.

I suspect the American Delta and Atlas types with their horizontal pivot pins do operate with a little more drill projection.  These more complex versions seem a bit more effectively engineered but apparently are too costly for the market.

Clive 

 This is just an idea for discussion, as I have not yet the skill or understanding to complete the task

The idea if possible would easily off set the cost of a machine if some of the prices mentioned are a viable option or at least help to justify the cost.

As small CNC mills / lathes are now becoming more available in the Model Engineering environment would it be possible to use a small diamond wheel and write a G-code program to sharpen a drill.

The size of the drill and the angle could be entered as data the datum could be the end of the drill the centre line of the quill or headstock is already known by the machine.

As I am writing this I can see that the position of the flutes would also have to be located.

Has anyone any further thoughts on this? Is already done?