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How to sharpen drill bits


simonr

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This is a fairly frequently asked question, but is difficult to explain in words.

I've drawn the diagrams below in the hope that it will help.

Although the subject of sharpening drills is HUGE, what I've drawn below will do for 99% of holes through most materials, especially mild steel.

If it doesn't work so good on a particular material, try making the drill bit more or less pointy.

If the drill bit keeps going blunt, slow down the drill speed.

sharp1.gif

And my top tip for easier drilling with big (>10mm) bits:

sharp2.gif

Si

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Although the subject of sharpening drills is HUGE,

:D

Nice one Si, I hope this makes it to the Technical Archive

Web thinning should also be considered when a drill is getting shorter due to regrinding as the shorter the drill the thicker the web gets, giving a much greater length chisel edge which in turn creates more heat and requires more power to drive. Be carful when thinning the web (reducing the chisel edge) it is not unknown for the drill bit to split vertically up the drill if the chisel edge is too small.

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:D

Nice one Si, I hope this makes it to the Technical Archive

Web thinning should also be considered when a drill is getting shorter due to regrinding as the shorter the drill the thicker the web gets, giving a much greater length chisel edge which in turn creates more heat and requires more power to drive. Be carful when thinning the web (reducing the chisel edge) it is not unknown for the drill bit to split vertically up the drill if the chisel edge is too small.

Cheers!

People have talked about drills splitting up the web - but I've never seen it! Must try harder!

Agree re the web getting thicker along the length of the drill - but figured most people will loose or break the bit before it becomes an issue & decided to keep it as simple as possible!

Si

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Nah me neither - thats a good tip <groan>

I sharpen my drills on a linisher, I find it a lot easier than the side of a grinder wheel.

I used to work with a guy who could grind a ø6" drill to perfection on a linishing belt, and then add chip breakers and web thinning with a 1mm grinding cut off disc!

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  • 5 years later...

Hello there

There is a small drill bit holder that can be bought. It holds/clamps the bits at the correct angle, it has variable angle settings and I have sharpened up to 16mm (reduced shank) with no problems it might do bigger but 16 is my largest. :blush: It might be a Draper tool.

I could never get the angle correct before for sharpening. Ended up buying new bits for each job, but not any more.

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When I was an apprentice one of the first things we made was a drill bit angle gauge. Then we spent a whole week grinding drills..........Oh what fun.

You can buy the little angle gauges and with a bit of practice grind drills very well.

Then I was taught to grind "fish tail" drills, bit like the spot weld drills which are brilliant for sheet metal as a normal drill can make a triangular hole in thin sheet.

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