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An idea for drill sharpening jig
sorveltaja:
Here the threads copied. About half turn for both, so When looking drill at the working end, cutting surface
there is more than enough: appears to be ~90 degrees:
NickG:
I'm a bit lost with this now! :scratch:
What is the rest of your contraption going to look like? Can't quite picture how it's going to work.
With the cheap grinding jigs, you angle the thing up at 59 degrees or whatever, the drill is held against a little thing that contacts the flute, then the jig is swung side to side grinding an arc. I think it depends how far down the flute you set it to hold the drill still that varies what relief you put on the cutting edges! But it'll be interesting if your thread jig removes the need for that, having said that, how are you going to make sure it's in the right position when you start grinding?
Nick
sorveltaja:
--- Quote from: NickG on September 30, 2009, 07:39:18 AM ---I'm a bit lost with this now! :scratch:
What is the rest of your contraption going to look like? Can't quite picture how it's going to work.
With the cheap grinding jigs, you angle the thing up at 59 degrees or whatever, the drill is held against a little thing that contacts the flute, then the jig is swung side to side grinding an arc. I think it depends how far down the flute you set it to hold the drill still that varies what relief you put on the cutting edges! But it'll be interesting if your thread jig removes the need for that, having said that, how are you going to make sure it's in the right position when you start grinding?
Nick
--- End quote ---
After reading texts that I wrote earlier, I must admit, that it can be quite confusing.
No other adjustments required, except drill tip angle (for example 59 degrees). Jig keeps drill's touching point with grinding wheel diagonal, if it works as I assume.
An animation of the process could maybe clarify the idea :borg:.
Here are the basepart, and drill holder. Red circle shows broken M3 tap(yet another SS 316 experience). As it is stuck there, why not use it as a guide for brass part's thread grooves:
Parts together with drill bit:
sorveltaja:
Mock-up, that shows the progress so far:
It needs support for the drill, and locking mechanism, that is to be used by the screw, that shows under the plywood piece.
I guess, that it would be simpler to combine the tube and plywood elements to one part.
tinkerer:
Trying to wrap my head around this. I am thinking you want to have the trailing edge of one flute at a lower rake than the leading edge. (that may not be what you are trying to accomplish) I believe, in production both, edges have the same rake. I think the most important part of sharpening a drill bit is consistency for both flutes, which is difficult to do by hand, thus the machines. Drills for steels, aluminums & plastics have different angles. plastics-25-30, aluminum, copper & brass 45-50 and steel 40-45. It is very important that both flutes have exactly the same cutting angles, cutting edges and lip clearances. Large dia. drills should have a back cut. To test the drill it should give an equal removal of material from both flutes.
It seems drilling aluminum gives the most problems. A lubricant called Boelube (you can google it and find many suppliers) is used by aircraft manufacturers and airline maintanence. It has a low melting point and lubricates as the heat builds up. I have drilled thousands upon thousands of holes in aluminum with no difficulty using the correct lube and techniques. Using the proper dia. pilot drill, then stepping up to final size with core drills or reamers also. Manufactures and airlines use the sharpening machines with good results and save a ton of cash doing so.
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