Neat trick for drilling hard materials

[awemawson]

Had a chap in today installing a woodburner, and he needed a 5 mm hole drilled in a cast iron collar for a self tapper to hold the stainless liner. Having melted the ends of his drill bits he asked for help! Fairly obviously the cast collar had chilled when cast and was as hard as a witches titty.

I took it to the workshop full of confidence that I had a suitable carbide tipped drill designed for tool steel. Chagrin - no drill small enough. So I thought why not try a suitably sized masonry drill - after all they are carbide tipped. Worked an absolute dream. And this was a masonry drill I'd been drilling hard brick with yesterday on hammer action! Certainly one to remember for the future.

[mattinker]

I have used masonry bits on hard steel, I found that resharpening the on a "green" stone, to make them resemble twist bits made them even better!

Regards, Matthew

[Fergus OMore]

I've just been 'Nauseate-ing'  on grinding on a Model Engine 'doo-dah' and really the trick with carbide drills is to use a diamond wheel rather than a green grit which fills everything with abrasive dust.
My first incursion was a wornout wheel that a local optical maunfacturer had rejected after doing a million lenses. There was enough of the grit left to work and a mate of mine has it on his Mark 1 Stent. People like Chronos are now selling better wheels.

Norman

[mattinker]

OK Norman, I should have said, re-shaping masonry bits to make the more like twist drill bits with what ever you have to grind carbide!

Green gives of a lot of dust  but is do-able, diamond wheels are better, what ever you avoid
 breathing the dust , carbide grinding is nasty!
 
Regards, Matthew

I've just been 'Nauseate-ing'  on grinding on a Model Engine 'doo-dah' and really the trick with carbide drills is to use a diamond wheel rather than a green grit which fills everything with abrasive dust.
My first incursion was a wornout wheel that a local optical maunfacturer had rejected after doing a million lenses. There was enough of the grit left to work and a mate of mine has it on his Mark 1 Stent. People like Chronos are now selling better wheels.

Norman

[Fergus OMore]

Yes, but you could think in terms of Four Facet Grinding.

I simply don't like carbide except for drilling brickwork etc but one of these horrid drills ( my opinion) and they could be used as lathe tools with a single cutting edge.

After all we Brits are in a state of Economic Depravity- or something like that

N

[jcrous]

I have also done it before after I have seen such drill bits on show at a trade show. They were carbide tipped and drilled through brake lineings and files at high speed.

I sharpened a concrete drill bit on a green stone to a positive rake and it worked. Just dip the tip regularly in water to prevent the brazing to melt. One con is that it chip quite quickly.

[Arbalist]

I've used glass drills to open up holes in hard materials.

[Miner]

You do NOT want to dip any carbide into water while sharpening. Thermal shock is a very real risk and carbide will not tolerate it. The same can happen while machining with it and applying coolant or cutting fluid too sparingly. Either use lots or cut dry.

Pete