Drilling granite wall

Green grinding wheel.

Lidl fom Sunday this week, £44.99 will do you.

Cheers, Jim

In which case that is much better than the fixed speed ones. Obviously still a bit large and lumpy, but sometimes that is an advantage.

Does it allow you to lock the chisel in a rotational position of your choosing?

Indeed, even the poorest SDS will run rings round a normal hammer drill.

on 01/06/2022, Rod Speed supposed :

Silly idea and doomed to fail.

The technique is to drill with a thin drill from one side and then enlarge the hole from both sides. Worked perfectly in my daugter's cotswold stone cottage.

In message <t79slr$hlf$ snipped-for-privacy@dont-email.me, Harry Bloomfield Esq snipped-for-privacy@harrym1byt.plus.com> writes

I rather liked TNPs *U through an opening/window suggestion. Unlikely to be precise enough for this job without great alignment care but perhaps useful for thinner walls and where extreme accuracy not needed.

It is amazing how many times you hear the "drill from both sides" suggestion... as you say, something very difficult to do in reality unless you can at least get a pilot hole right through the wall.

charles formulated the question :

What does work, is a small pilot hole bursting through at the far side, then a much larger core cutter, where the core is cut from both sides.

Yep and 10mm is a pilot hole size.

Fine when you want a 4" core through a wall, but useless for a 10mm hole!

(you will be hard pushed to find a long SDS bit in anything less than

Have you got a 10mm drill long enough?

Gosh - that's what I suggested.

Which, you might appreciate is not actually much use for the OP who only wants a 10mm hole through 400mm of masonry.

This is not a time for cheaping out, or dodgy "drill both sides" hacks.

Just buy a long 10mm SDS bit like:

Yes.

Is it generally better to start off with something shorter if available to get the position and line you want? Or is it just me who finds it difficult to start with very long bits?

When I've been using a 1 metre long drill I've used a bit of wood set up with a spirit level to run the drill bit along when staring the hole.

and in a 600mm wall you only have to be out by a few degrees from square (up, down, right or left) to guarantee failure

Masonry drills don't always follow a smaller hole, so it's not a foolproof method. It helps to use a series of drills of gradually increasing size. 10mm SDS drills are available at any reasonable length, so I would always start with 10mm, then drill 12mm from both sides, then

In the old days drill sets with extension pieces were used. They seem to have fallen out of favour.

Bill