Here in the UK you can hire a "core drill" with or without a SDS drill to d= o=20 this job. Core drills to buy are around =A340 for a 107mm diameter by 150mm= =20 deep You could even consider asking a local plumber or gas engineer if they can= =20 do the job for you and save some money as they often have these for making= =20 holes for the boiler flues. Dom -----Original Message-----=20 From: RussellMc Sent: Tuesday, August 20, 2013 12:46 PM To: Microcontroller discussion list - Public. Subject: [OT]:: "Drilling" concrete - ideas sought Short: Ideas sought for low cost low effort way of cutting a say 4"/100 mm dia hole (or larger) through 6" / 150mm concrete. Aggregate but no steel. Can take some days if effective and wholly hands-off. Note: 20mm tungsten carbide tipped drill bit + hammer-drill is low cost (but costly on me) but far far from low effort. _________________________ I'm enlarging a drain hole through the base of a wall in an old concrete swimming pool. A walled garden will/may happen in due course: http://bit.ly/SECRET_GARDEN So far it's a malodorous ex-duckpond. Concrete is about 6" / 150mm. Reasonable amount of aggregate but no obvious steel where I am drilling. I have drilled a hole with a 20mm carbide tipped bit and can enlarge that somewhat by butchery. I need a substantially larger hole that can handle mud sludge and garden ooze that will invariably happen even with care. I'd guess a 100 mm square hole or a wider lower slot would suffice. (200mm x 50mm maybe - may be a bit low). Access is reasonable but not stunning. I can make a large enough hole in time with successive 20mm holes. These are hard on the bit, the drill and me - quite a suibstantial amount of effort required for one hole through. I've been thinking about other possible methods that could be achieved at modest cost. Any superior ones would be welcome. - Fire / heat : - Set up gas air feed through the hole with flame burning within the hole proper if possible. Expectation is that the concrete strutcure will be weakened and aid mechanical enlargement. - Gas torch on wall face.I recall concrete "spalling" under a tight gas flame. No experience of "gas cutting" concrete. - Electric radiant heater against wall. Hmm - electric paint stripper worth a try. Could heat Nichrome element in hole. Cut: - DIY hole saw: Most hole saws are not targeted at this sort of depth - and a suitable carbide or diamond faced one is liable to be costly for one off use. I could probably "relatively easily" [tm] fabricate a rotary cutter with a long arm (6"+) and a carbide cutter from a drill or similar on the end such that the cutting face is large than the driving rod so that it can cut a 6" plus deep hole. Single arm may do. Two for balance not a terrible idea. 3 maybe even better. Arm flex not important if cutter can be maintained against wall. Drive this at moderate speed with whatever motor suits, and mount the assembly on a hinge or parallelogram assembly and apply spring pressure or weight so it sits against wall and drills. Slow (hours to days) but unimportant if it works. Can water lubricate with hose misting. - Water jet? Best available would be domestic "water blaster". This worked excessively well on a stucco surfaced house long ago when due care was not taken :-). I'd expect it to be too slow on concrete. I don't think this justifies me trying to implement or hire or ... a garnet / grit / ... cutter. - Perhaps a swinging impactor / chisel would allow a hole to be slowly chiselled - horizontal pile-driver style. Not hard to set up given a slow turning shaft. Cut / burn hybrid: - LASER: Do not have CO2 which may well work. Have large glass HeNe of yore - but probably in 10 mW if that range =3D forget it. Hmm. DVD LASERS? Freeze? Dissolve? Explosives: No :-). While my experiences of long ago are probably still up to fabricating sometjing that would 'do the job', how large a job it did would be uncertain, possible repercussions are severe and regulatory authorities would be sure to not come to the party. Or ... ? Or hire something (again) :-). Russell --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist=20 --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .