Cob: Re: Cutting holes in cob

[baco@pacinfo]

I wonder if a pressure washer and wet/dry vac would do the job...

Brian Bray
Eugene, Oregon


----- Original Message -----
From: "Shannon C. Dealy" <dealy at deatech.com>
To: <coblist at deatech.com>
Sent: Friday, July 04, 2003 11:15 PM
Subject: Cob: Cutting holes in cob


> On Fri, 4 Jul 2003, Taylor Publishing-DirtCheapBuilder wrote:
>
> [snip]
> > Elishiva said  the cured cob was so hard it took 3 long weeks with a
> > pick ax (tough manual labor) to open a small window portal through the
> > thick cob.  They assumed it would be easy too...we all keep trading this
> [snip]
> > Anyone else have an easier time of it? We need anecdotal evidence so the
> > real work tally can be known.
>
> The difficulty is going to vary greatly depending on your mix
(particularly
> if there is alot of rock in it), how dry it is, and how you approach
> making the changes.  Depending on what you are trying to do, different
> tools and approaches may be better.  Some things I have done:
>
>   - 3" hole through a wall using a hole saw and electric drill, worked
>     fine until it hit the core of the wall which still hadn't dried,
>     then the cob would fill up the hole saw and I would have to stop every
>     minute or two to clean out the hole saw blade unit.  Time to drill
>     a 3" hole through 16 inches of cob was about 30 minutes.
>
>   - removing cob from under a window frame to relieve stress due to
>     an unexpected degree of shrinkage and settling.  Used an old
>     (junk) broad bladed wood chisel and hammer to cut the cob away.
>     It took quite a bit of time, but mostly due to making small cuts
>     in order to avoid damaging the window frame.   It works quite well
>     for precise triming of areas.
>
>   - Reciprocating saw (sometimes called a "saws-all") with a heavy duty
>     blade works pretty good for many applications
>
>   - Small hole in a hurry (such as for running wire through a wall), a
>     piece of solid steel rod longer than the wall is thick can be driven
>     through the walls with light weight hand sledge in about a minute.
>
> I haven't had need of any larger scale holes, though I will need one about
> a foot across in the near future.  I suspect that the fastest approach
> might be to get or make a large broad bladed chisel with a really long
> shaft and drive it through the wall repeatedly to cut the outline of the
> hole, then knock the center out with a large/heavy sledge hammer, and trim
> the hole afterwards with a reciprocating saw.  Alternatively, it might be
> possible to do it directly with a good reciprocating saw and some really
> long blades (though probably you would have cut the hole from both sides
> in order to get all the way through the wall).  It might be interesting to
> try using a wood splitting wedge (I think I have seen some with long
> handles) and a sledge hammer to cut the hole.
>
> FWIW.
>
> Shannon C. Dealy      |               DeaTech Research Inc.
> dealy at deatech.com     |          - Custom Software Development -
>                       |    Embedded Systems, Real-time, Device Drivers
> Phone: (800) 467-5820 | Networking, Scientific & Engineering Applications
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>