Hole for pipe through wall

rt18 · 4 Nov 2007

I got this 22mm copper pipe, sitting in a 25mm hole in my cavity wall. But it needs to be sleeved, see. So I need to make a bigger hole, right? But you can't get masonry bits any bigger than 32mm (from ScrewFix anyway, and even that one's a special).

I got a diamond core cutting set for putting 100mm holes in me walls for extractor vents etc., but that uses a guide drill bit of about 10mm diameter. So, if I tried to put a 38mm core bit through the old hole, the guide bit would just waggle about in the 25mm hole, making it very difficult to hold straight. I bet this would produce an awefully messy result.

My question is: Without drilling a fresh new hole next to the old one, how do make my 25mm hole a 35mm hole?

EliteHeat · 4 Nov 2007

You could make a guide for the larger hole, or you could just get a mate to help steady the drill until it digs in a bit - works for me anyway.

Terrywookfit · 4 Nov 2007

Buy a 28mm Diamond core drill for 22mm pipes or 35mm for 28mm pipes etc etc etc !!

chrishutt · 4 Nov 2007

rt18 said:
I got a diamond core cutting set for putting 100mm holes in me walls for extractor vents etc., but that uses a guide drill bit of about 10mm diameter. So, if I tried to put a 38mm core bit through the old hole, the guide bit would just waggle about in the 25mm hole,..

Why not drill the bigger hole slightly away from the existing one? Then you can use your existing drill. Alternatively, can't you stick a bit of wood dowelling or similar in the existing 25mm hole to give your 10mm pilot drill something to bite into? Once you started the diamond drill 20mm or so into the wall it won't need the pilot drill to continue in a straight line.

rt18 · 4 Nov 2007

Cheers everyone.
Seems I'll give the 38mm core bit a go. Will try to pack hole with a 25mm dowel or similar to give the pilot something to bite, otherwise will have to use sheer determination to keep it straight

namsag · 4 Nov 2007

Why do you want to drill a hole as big as 38mm to take a 22mm pipe ... A 28mm (inch) hole and a bit of 28mm (inch ) pipe as a sleeve is suffient

ChrisR · 4 Nov 2007

22mm pipe needs a 32mm sleeve in the regs - I read it the other day. Reason - answers on a postcard

Small cores are dead easy to do without a pilot bit.
Angle the drill at about 30 degrees (up at the sharp end) and let the bit spin in your cupped hand. If you're a poof, start slowly.
Once you have the lower half of the circle cut into the wall, bring the drill up and in you go. I usually use a 24v cordless SDS for littluns.

See later.........

namsag · 4 Nov 2007

What regs chris it is not in the corgi book and raised this point with them the other week and there answer was as long as it can move freely

ChrisR · 4 Nov 2007

Saw it in the Viper book, table copied from the BS I assume.
Latest BS6891 I have is 1998 which I guess is not the latest. That doesn't give sizes.

gas4you · 4 Nov 2007

I've never heard of this reg either

. I always just sleeve with next size up copper tube and seal internal end.

twgas · 5 Nov 2007

I just chisel out enough for the end of the bigger drill, then away you go

rt18 · 6 Nov 2007

...for a laugh, thought I'd report on how I managed to increase size of the hole

First of all, had no way of creating a dowel of wood large enough to sit in the existing 25mm hole (and didn't fancy hand sawing a circle out of mdf), so I took the 38mm diamond core drill straight to the hole. Result? A score in the plaster about a metre long in a straight line across the wall!

Turns out I can't just "use sheer determination to keep it straight"

So I invented a tool instead. Took a 38mm wood hole saw, and managed to attach it to a 22mm flat wood bit!

Using the flat wood bit as a guide in the hole, I was able to use the hole saw to create the beginnings of the larger hole, but only in the plaster of course. That gave me enough depth to get the diamond core bit in and off I went

Bodged, but successful

Biggles.. · 6 Nov 2007

For those questioning pipe size sleeves, a pipe require 3mm air gap all round(domestice pipe size, upto 6mm for commercial) therefore 22mm OD cannot be sleeved with 28mm OD because the internal would be about 26mm. 22mm requires 28mm ID.

But we all know what gets fitted.

chrishutt · 6 Nov 2007

lcgs said:
For those questioning pipe size sleeves, a pipe require 3mm air gap all round...

Why?

Biggles.. · 6 Nov 2007

Not entirely sure, thermal expansion?structural movement?. Have asked and no-one can give a "its because".

Unforunately those are the rules so thats what you should go by.

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Hole for pipe through wall

namsag

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