Hi Russell, You -might consider- some sort of acid for this task as well. No I am not talking about LSD, muratic or hydrocloric acid -might- do the trick. y. On Tue, Aug 20, 2013 at 1:46 PM, RussellMc wrote: > 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 obvio= us > steel where I am drilling. I have drilled a hole with a 20mm carbide tipp= ed > bit and can enlarge that somewhat by butchery. I need a substantially > larger hole that can handle mud sludge and garden ooze that will invariab= ly > happen even with care. I'd guess a 100 mm square hole or a wider lower sl= ot > 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 wor= th > a try. Could heat Nichrome element in hole. > > Cut: > > - DIY hole saw: Most hole saws are not targeted at this sort of depth - a= nd > a suitable carbide or diamond faced one is liable to be costly for one of= f > 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 su= ch > 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 day= s) > but unimportant if it works. Can water lubricate with hose misting. > > - Water jet? Best available would be domestic "water blaster". This worke= d > excessively well on a stucco surfaced house long ago when due care was no= t > 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 yo= re > - 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 u= p > 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 > -- > 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 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .