On Wed, 15 Sep 2010 13:21:37 -0700, Tim Wescott
wrote:



Yup. You could use a countersunk screw, but there's not much meat there
to thread a fastener into. You could do something like #4 screws
(countersunk, of course) into the sides -- but I only suggest that
because I have a master's degree in engineering, not because it actually
has a chance of working.

No need to apologize for bailing out at MS?? level, Tim. G

4-40 flathead screws with Loctite would work just fine. Even 2-56
screws would probably suffice. It's not a fix a grease monkey would
think of, but it'd be easy peasy for a machinist or gunsmith.

A good braze would be stronger, but all that's needed here is
"enough". Gunner sez a dozen pounds. Call it 50 for a bit of margin.
A bad braze with micro cracks in the surrounding casting, bad wetting,
or foaming of the braze alloy would very likely fail, and the
likelihood of getting a bad braze is significant for folks like me and
Gunner having no experience brazing with TIG. Torch brazing ain't on
the menu here unless the head is stripped and preheated, and even with
that there is significant risk of warping. The advantage to TIG, if
it works, is that you're in and out of there quick as a surgeon with a
golf date, leaving a very limited heat-affected zone. The question is
what happens in that very limited HAZ. Any crack upon cooling is a
failure. Cast iron varies a lot in tolerance; some castings can be
welded or brazed without difficulty while others are impossible. I
have successfully repaired fractures in the intricate cast iron
lattice work on the treadle of a vintage Singer sewing machine,
totally failed on the exhaust manifold of an '80's vintage Japmobile.

So I'd either learn and verify a TIG brazing process experimentally on
scrap stock, or I'd drill, tap and use flathead machine screws.

I'd go with TIG if I could find some cast iron to practice on, because
I have lots of time, 3 working vehicles and no urgent need to be
anywhere other than medical adventures with Mary and Mayo. If I were
in Gunner's sit, I'd go with machine screws.