Thread: Hand-sharpening of drill bits

Originally Posted by KevinB

I need to sharpen some dull drill bits.
I don't want to pay dozens of dollars for some fancy-doodle mechanised system B

Is a bench grinder too fancy?

Kevin I have a commercial jig not used yet as i have not set it up but there are many plus and with your skills easy to make.

Originally Posted by underfoot

Is a bench grinder too fancy?

Have a look at this site, it explains how a drill works/cuts.

Please read it completely and fully comprehend what is actually written there.

There is NO mystery about it at all, once you fully understand how a drill actually does the cutting, then you sharpen the drill accordingly.

Drill Sharpening

If you really want to go the route of using a jig, then here is some further reading for you.

Drill Sharpening

Top link, thx!!

I was taught how to do it by hand and the description in the link is excellent!

Originally Posted by Sebastiaan56

Top link, thx!!

I was taught how to do it by hand and the description in the link is excellent!

(This is supposed to be the "What he said" smilie, but it won't load). Anyway, I agree, it is a very good description.
+ The "neutral rake" used for brass is the same as for acrylic.
We were taught to throw away any blunt drill under 4mm diameter as "they aren't worth the bother and you will probably destroy the hardening anyway".

Originally Posted by Crunchie

We were taught to throw away any blunt drill under 4mm diameter as "they aren't worth the bother and you will probably destroy the hardening anyway".

That may have applied to carbon steel bits, but the new HSS babies will burn you long before you can get them hot enough to destroy the temper.

Hand sharpening bits is a handy dandy skill to have. Takes practice, but is worth the effort to learn a million times over once you get the knack of flicking your wrist just so and holding your mouth the right way.

OK, I read the sharpening post twice. And some who did it all his working life has shown me the basics years ago.

Let me see if I have it right though, He has 118 degrees over the cutting edge. When he talks about 5 degrees is he saying that the angle over the trailing edge is 118 + 5 + 5 = 128 degrees.


Peter

Let me see if I have it right though, He has 118 degrees over the cutting edge. When he talks about 5 degrees is he saying that the angle over the trailing edge is 118 + 5 + 5 = 128 degrees

No, all he is saying is that there is a 5 degree relief behind the cutting edge so the trailing part of the drill doesn't rub in the hole.

Originally Posted by _fly_

Let me see if I have it right though, He has 118 degrees over the cutting edge. When he talks about 5 degrees is he saying that the angle over the trailing edge is 118 + 5 + 5 = 128 degrees.


Peter

Whoo there, hold the horses, there is NO need to try and get the absolute exact perfect angles, that's for the drill manufacturers to get right.

All you got to do, is make sure you have a cutting edge on the drill and relief behind the cutting edge, so that the cutting edge can cut.

If you want to get all involved in the exact angles, well your going to be extremely disappointed, what with all the dud bits your going to ruin, trying to get those EXACT angles.

If it cuts after you've sharpened it, then your good to go, as you get better at sharpening drill bits, then go back and have a try for the exact angles.


So, near enough will be good enough for starters.

OK, that makes sense now. I'm just trying to reduce a bit behind the cutting edge.

Originally Posted by mardtrp

If it cuts after you've sharpened it, then your good to go, as you get better at sharpening drill bits, then go back and have a try for the exact angles.


So, near enough will be good enough for starters.

I disagree. Why learn bad habits. A properly sharpened drill bit will drill better, faster, cleaner holes and will retain it's edge for longer.
If it's worth doing etc...It only takes a minute to check the angle and adjust if it's off. It's also worth finding a chart with appropriate angles for different materials. A couple of degrees can make a big difference to how a drill performs.
I may be pedantic but that's my 2c worth.

Oh and to answer the OP, I wouldn't even consider sharpening drill bits with a file and stone unless you have an awful lot of time to kill.

drill point sharpening.jpg

drill point geometry.jpg

These are copies of the pages from the engineers black book and show the various details for sharpening drills.

The actual angle isn't that important as that the leg length is the same.
See what you think.

Robert

Originally Posted by NCArcher

I disagree. Why learn bad habits. A properly sharpened drill bit will drill better, faster, cleaner holes and will retain it's edge for longer.
If it's worth doing etc...It only takes a minute to check the angle and adjust if it's off. It's also worth finding a chart with appropriate angles for different materials. A couple of degrees can make a big difference to how a drill performs.
I may be pedantic but that's my 2c worth.

Oh and to answer the OP, I wouldn't even consider sharpening drill bits with a file and stone unless you have an awful lot of time to kill.

Before this becomes totally inflamed, please go and read the original question again.

All he wants to know, is how to sharpen a drill because he can't do it.

Now why try and get all pedantic, about a couple of degrees on the drill tip angle, hey, if he can just sharpen one drill bit and it cuts, then he's starting to get the idea of how to do it.

Once you got the idea of how to do it, then start getting pedantic about it, don't get all pedantic to start with, or he'll just bugger up heaps of drills and turn him of the idea totally.

How about cutting him a bit of slack to start with, instead of trying to be so pedantic about this.

Its not an art you acquire overnight, I spent hours at grinding wheels when I was an apprentice fitter/machinst, I was taught by the best old guys who really knew how to sharpen drills ,its all in the wrist movement.