Calvin,
It sounds like it needs to be annealed. Electrical welding (MIG, TIG, or Arc)
create very high temperatures in localized areas. After the welding the heat is
wicked away into the surrounding metal resulting in a very hard area in the
vicinity of the weld. This is way welds will often crack in vibration
environments. The answer is to heat the area in an oven to 1600 degrees and
then let it cool slowly. If you have a heat treating house in your area, they
do this all the time, and should charge much. You can try it yourself by
heating the entire flange and adjacent exhaust tubing with a torch until it is
red hot. This will require an Acetylene torch. Keep it red for about 10 min.
Then reduce the heat input slowly until it is no longer red. Try to take 5-8
minutes for the cooling. Then let it air cool. Do not put it in water.
Craig Wright
Calvin Krug wrote:
> I'm hoping one of you mechanical-types can help me out. I recently had a
> steel exhaust manifold flange welded, and now I'm trying to redrill the
> hole for the stud. I can't find any drill bits that will cut through the
> welded steel. I've tried regular high speed drill bits, titanium-coated,
> cobalt, and most of them won't even touch it. Yes, I'm using cutting oil.
> I've managed to get about 1/8" through, but the more I try, the less effect
> I seem to have. Any ideas?
>
> Calvin Krug
> trying to rebuild my MGB
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