[Steam-engine] Repro Castings

[James Mackessy]

Hi Andy and All;
     We have a small brass and bronze foundry near us and we have had some
valves, nameplates and other things loose cast from original parts. We build
up
threaded areas with electrical tape, fill holes with a stiff putty, similar
to modeling
clay, and cast from there. The thing you need to be aware of is shrinkage.
The
reproduction parts will be smaller than the original, so threads and bosses
that
mate with other parts will need to have a little "machining stock" built up
on them.
Allowances for shrink vary with the thickness of the metal and size of the
casting
within a limit set by the material being cast. For example, a cylinder head
in cast
iron that needed to finish out at 12" diameter would require a pattern
12-1/8" in
diameter, plus any allowance for machining stock off to finish. The 1/8" is
the
shrinkage per foot that can be expected from cast iron. For many parts it is
not
necessary to worry about it if the repro is slightly smaller, but for items
that must
fit existing mating parts, pay attention to the mating areas. We have found
that in
some cases to get a matching part, we have had to make a pattern with the
proper allowances built in so the finished castings match the original
dimensions.
Some foundries will take care of all this for you, but it's good to make
things as
easy on them as possible. Dropping complicated patterns and core boxes off
at
a foundry that doesn't want that kind of work can lead to a long wait and a
large
bill. On the other hand, if you bring a few pictures of your project along
and are
lucky enough to find the right foundry, you can generate some enthusiasm for
the
job and learn a lot in the process. Good Luck!
Best Regards;
Jim Mackessy
Syracuse, New York, USA
----- Original Message ----- 
From: "Andy glines" <pioneersop96 at yahoo.com>
To: "Steam" <steam-engine at lists.stationary-engine.com>
Sent: Tuesday, February 15, 2005 3:30 PM
Subject: [Steam-engine] Repro Castings


> I am gathering a few pieces that I need to have
> reproduced in order to complete the restoration on the
> huber.  For now, I intend to use original castings as
> patterns.  How do I need to prepare these castings
> before shipping them to the foundry?
>
> =====
> Andy Glines
> Evansville, IN
>
>
>
>
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