Loooooong drill needed

[Tim+]

To alter the wiring of some downlighters in our kitchen/dining room, I need to pass a wire from downlighters on one circuit across to a couple of lights currently on another circuit.

The problem is it's a vaulted ceiling with no access above (short of lifting roof tiles) and I'll have to cross a couple of ceiling joists. I could cut the plasterboard and "stitch" the wire over and then replaster but I'd rather not. If I could find, make or adapt an existing drill to make one at least 700mm long, I could probably drill obliquely from both ends through the existing downlighter holes and thread a wire through.

Does this sound reasonable? I've found drills up to 600mm on line but they're not going to be long enough.

Tim

[Murmansk]

Would one of these be any good?

[Dave Liquorice]

I've a set of 1m SDS drills but they are crap at drilling timber...

Best bet I should imagine is drill extension pieces rather than a single piece drill.

[polygonum]

Masonry/SDS - no problem:

if that was a bit expensive:

[Tim+]

That's my thinking but haven't found anything suitable yet.

Tim

[Tim+]

Yeah but, masonry drills absolutely suck at drilling wood. You might as well use a blunt stick. Don't have an SDS drill either. :-(

Tim

[Dave Liquorice]

Auger bit accesories?

[John Rumm]

The spade bit extension shafts are about 300mm long and can be cascaded. Hence you can drill one in, and then stick another on. You can repeat several times if you need to.

[Tim+]

I found bits up to 600mm but I don't know if you can get extensions that will fit. As it's a "one off" job, I'm wondering if it might be easier/cheaper to just make a crude drill.

Tim

[Owain]

Do drain rods have enough strength in torsion?

Owain

[Nightjar]

As you only want to drill wood: Take a long piece of carbon steel rather smaller than the diameter you want. Heat one end and flatten equally from both sides (e.g hammer and anvil) until wider than the hole you want. Grind to a V-tip of the correct diameter. Back off the edges of the V tip to form a cutting edge. Harden and temper. You now have as long a drill as you want. It won't be brilliant, but you won't have spent a lot of money for a one-off use and will do the job well enough.

Colin Bignell

[Tim+]

Hmmm, that could work. Cheers.

Tim

[mike]

Either of these any use?

[polygonum]

You needed an excuse! I didn't specifically look, but you always used to be able to get some pretty darned long non-SDS masonry bits. Or it is an excuse to do what you really want to do and buy yourself an SDS...

There are extension pieces that are usable with various flat bits or augers. I saw up to 600 mm. Can they be combined without too much danger?

[Tim Lamb]

I have extended flat wood drill bits by brazing on a bit of tubing or socketed rod.

Not tried anything that long though and I expect the usual drill speed would cause such a long shaft to whip. Might be possible in stages where the previous hole supports the shaft.

[Andrew Mawson]

What I have done several times in the past is to turn the shank end of the drill down in the lathe, and braze it into an axially drilled hole in a suitable diameter and length of mild steel. If you are in striking distance I'll do it for you - takes less time than to type this! I'm TN33 (East Sussex) if it helps.

AWEM

ps I used a wood auger recently that had a hex shank. Using suitable socket and socket set extensions I made up a rather wobbly long auger that went through the timbers of my barn ok.

[PeterC]

If you get the bit in a non-SDS chuck just right there's very little wobble. I use this method if I want a 'slack' 6mm hole and don't have a 6.5mm drill. _However_ the small wobble on a 150mm bit might be too much to handle on a

1m bit.

[polygonum]

Makes me wonder, is there any effective DIY way of sharpening a tungsten carbide tip on such a drill? Sort of converting it to a Bosch multi construction style. :-)

(I do appreciate that if it were that easy to get good results, it would have been talked about many times. But was thinking that it might be possible to manage significant improvement.)

[Tim+]

Sounds doable. I'll give this a go first. Cheers.

Tim

[Tim+]

they look good. Auger would be nice but pricy I imagine. I'm going to have a go at making a crude drill first though. If that doesn't work then I'll go for the Hall-fast one.

Many thanks again.

Tim