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Perfectly ground Twist Drills every time.

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Ady112/05/2015 14:43:49
3859 forum posts
522 photos

I recently got some good drills from the relative of a long gone British Aerospace engineer who did stuff like gyroscopes and tooling for surgeons

His drills all have a tiny land ground at the point to extend the drilling point workzone



John Stevenson12/05/2015 15:29:18
5068 forum posts
3 photos

That's called point thinning. Very common because as a drill reduces in length the central web gets thicker for strength.

Vic12/05/2015 15:35:25
2607 forum posts
20 photos

I never knew that John. wink

AndyP13/05/2015 16:17:17
189 forum posts
30 photos

I got one of the Holzmann drill bit sharpeners mentioned today and have been playing with it this afternoon. Seems a solidly built unit and the "plastic" bits are thick and hard rather than flimsy. There is a video on the German parent website here .

I am not sure about the angles it produces though, the first grind, I'll call it cutting looks too shallow to me and the clearance angle grind which is done second barely touches the back of the cutting edge.

First picture shows after the main grind of the cutting edge...


And after the clearance angle has been ground


Not sure whether to return it or not.


Chris Shelton13/05/2015 16:48:37
92 forum posts
46 photos

Hi Andy,

I also bought one in the end, very pleased with it, but before you grind the clearance angle, you need to reset the drill position in the holder again.



Edited By Chris Shelton on 13/05/2015 16:49:14

AndyP13/05/2015 17:13:30
189 forum posts
30 photos

Hi Chris,

That certainly takes more off but neither the instructions or the video mention resetting the bit between grinds, the video clearly shows doing one then the other all in one camera shot. It doesn't look right to me :-


Chris Shelton13/05/2015 18:00:49
92 forum posts
46 photos

Hi Andy

Not sure how to put youtube links on the forum, but if you look at the tradetools tv review of a re-badged version of the drill sharpener, he states you should reset the drill after sharpening.


AndyP13/05/2015 22:20:08
189 forum posts
30 photos

Thanks Chris, so it does, link here , now that is annoying, 2 sets of contradicting instructions for what appears to be the same device. I feel more inclined to believe the manufacturer though.


Bowber13/05/2015 22:30:42
169 forum posts
24 photos
I learnt to do mine by hand while an apprentice. I was a jig and die maker at K shoes and had to drill thousands of holes a week so we learnt to do them by hand, it's been handy since as I. get to resharpen my crappy cheap drills.
Dave Halford14/05/2015 12:49:38
921 forum posts
9 photos

I would have said from the second pic the drill has been thinned too much. The cutting edge looks to have gone in the center.

I've got a Holzmann myself and I've noticed it's quite sensitive to hand feed variation which can give an off center grind effect if you don't take care.

It shouldn't need resetting for the second grind unless the second grinding station is set too high.

All I have done is regrind on the same setting if it looks off and that seems to fix it.

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