By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

Perfectly ground Twist Drills every time.

All Topics | Latest Posts

Search for:  in Thread Title in  
Ady112/05/2015 14:43:49
avatar
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

drill-land1.jpg

drill-land2.jpg

John Stevenson12/05/2015 15:29:18
avatar
Moderator
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...

first.jpg

And after the clearance angle has been ground

after.jpg

Not sure whether to return it or not.

Andy

Chris Shelton13/05/2015 16:48:37
avatar
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.

HTH

 

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 :-

reset.jpg

Chris Shelton13/05/2015 18:00:49
avatar
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.

Chris

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.

Andy

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.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Support Our Partners
EngineDIY
Eccentric July 5 2018
cowells
emcomachinetools
ChesterUK
Warco
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest