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
> --
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Talk to a local contractor with a drill. I just had a 4" dryer vent drilled
through
a stone wall (not concrete 10" of stone) took about 15 minutes for a guy wi=
th
the right tools. He was working on some other things here and said sure no
problem
and he was right.

This is a problem not worth thinking about.

w..



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