I need to drill two long holes to take some 28mm pipe for my Rayburn install. Biggest bits I have are 18mm and 1m long - they have drilled the pilots succesfully but I need to enlarge these now. I literally need it for one job. Where is the cheapest place to pick one up? Screwfix have dewalt stuff for over £100 but I wasnt looking to spend that much! Probably need 30mm or 32mm diameter to give a bit of leeway for the pipe to pass through.
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eLuSiVeMiTe
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Drill 18mm hole into a spoil board and use it as a guide to start the hole. The pilot on the core drill should stop it wondering too much from your original pilot.
eLuSiVeMiTe
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Alternatively turn a smooth pilot to suit. They're just a taper fit on core drills.
zeppelin builder
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how about welding 2 or 4 10mm bits about 2 inches back to the sides of the 18 mmdrill
the flutes arent hard and you only need the tips to cut and the 18 would centre it
123hotchef
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does it need to be 1m long
Yep. These walls are thick!!
123hotchef
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could u do half from each side though? so 500mm?
Johnnybravo
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Sds Max. Sod’s law, I threw one away in the second to last skip. 30mm. Was a cheap and cheerful thing of dubious parentage. Did the two holes I needed,but didn’t look like it would survive many more . Probably would have done for your job though 
Maybe. Its hard to explain but i am trying to hit a narrow space in between old stone and breeze block. With rubble and loose stone in between.
123hotchef
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but the piot is there, soit should be easy to meet now
Seadog
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From my experience of thin walls with loose rubble, that its going to jam a thousand times. Good luck.
brightspark
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been there and got the tee shirt its exasperating 
Kram
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Diamond bits are your answer. Trying to enlarge with sds/carbide tipped hammer drills will be painfull!
Likely cheaper elsewhere but this shop are reasonably good, imported stuff tho.
I think TheRange sell 30m/35mm and long extensions?
10mm hex drive.. make/buy extension... Send a pm if you cant find one, I can make one up.
Yes you need to pull the drill and push the center out very often.
Likely cheaper elsewhere but this shop are reasonably good, imported stuff tho.
I think TheRange sell 30m/35mm and long extensions?
Segmented Diamond Hole Saw Core Bits 6 to 100mm
Suitable for cutting brick, stone, concrete, reinforced concrete, marble, granite, and ceramic.
www.aimtools.co.uk
10mm hex drive.. make/buy extension... Send a pm if you cant find one, I can make one up.
Yes you need to pull the drill and push the center out very often.
So a few pics.
Kitchen side is easy. Thats a breeze block and the holes i need to follow are the two large ones one above the other
This is the other side which is between original outsode wall and rubble and breeze blocks
My pilot holes come into this space you can just see that there are breeze blocks about 12mm away from the old stone wall. This gap is the only place i can go and do this job neatly.
Kitchen side is easy. Thats a breeze block and the holes i need to follow are the two large ones one above the other
This is the other side which is between original outsode wall and rubble and breeze blocks
My pilot holes come into this space you can just see that there are breeze blocks about 12mm away from the old stone wall. This gap is the only place i can go and do this job neatly.
