Weld or Braze ?

One of my never-ending projects is the restoration of a '39 Harley . One of
the broken parts is the transmission sprocket cover . It's made of cast iron
, and one of the bolt hole/cover standoff's is broken out . I have machined
a part out of mild steel , and ground out the jagged edges on the cover to
fit . Both pieces will be bolted to the tranny end cover for correct
alignment .
I was planning on brazing it , but am concerned that heat distortion will
be a problem . I'm also concerned about strength , as this cover supports
the throwout bearing for the clutch . I'm limited on arc welding eqpt to a
flux core wire feed (Lincoln Weld Pak) , but the guy at the machine shop
around the corner from work will likely weld it for cheap if I decide to go
that way .
Reply to
Terry Coombs
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Brazing is really cool, but I would be uncomfortable doing it on a highly-stressed part. I'm no expert, but if I were left to my own devices I'd probably make the repair part out of cast and see if I could find somebody willing to get it hot and weld it with a cast-iron stick -- or I'd restore that old forge I have out back and do it myself (which may be worse than just using JB weld, given my welding skills :).
Reply to
Tim Wescott
I brazed the lower kingpins back into my '58 Chevy 4X4 front axle , been several years and they're still hangin' in there . This part isn't what I'd call highly stressed , and there are 3 other bolts .
I've never machined cast , but I think I know where there are some old window balance weights ...
The problem with getting it hot is that the cover I'm using to align it is also cast , and is highly machined . It also has a brass bushing (countershaft , which mounts the kicker arm) and a (loose roller) bearing race in it for the mainshaft . I have no idea what stresses are in the cover , and if I warp it , I'm screwed . Parts for this tranny are rare and expensive . -- Snag aka OSG #1 '76 FLH "Bag Lady" "A hand shift is a manly shift ."
Reply to
Terry Coombs
Both pieces will be bolted to the tranny end cover for correct alignment . I was planning on brazing it , but am concerned that heat distortion will be a problem
Reply to
If it is cast iron. you need to use a nickel rod. Pre heat the parts to around 400 deg. in a oven to " boil " out all the oil. Then while hot weld.
I used this method years ago to make a vega steering box work on my 29 dodge street rod. The oven baking and nickel rod were mentioned very specificly in all the articals I found on welding cast iron.
The Part has over 200,000 miles on it and has withstood the shocks of Idaho, Washington, Oregon and worst California roads.
Steve E.
Reply to
Steven E. Eyrse
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*Don't*! Window counterweights are probably the worst possible cast iron in existence. Unknown alloy, chilled in casting, full of carbide inclusions, probably destroy a brazed carbide lathe tool. (At least it did for me, the one time that I tried to use it for anything other than as window counterweights.
You might be able to heat it up enough and cool it slowly enough to make something machinable out of it -- but for something which you really care about -- buy some good quality cast iron. It is not *that* expensive.
Good Luck, DoN.
Reply to
DoN. Nichols
It would be primo material (white CI) to make malleable iron out of - just heat it to 2000F or so over 24 hours, then cool as slowly.
Get x-rays of the stuff before machining though, since it's full of holes.
-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @
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Reply to
Tim Williams
What about JB welding it in place, then tack welding it and remove the JB and finish it off the cover?
Reply to
Nick Hull
A well-made brazed joint in cast iron can be around 65,000 psi tensile strength. (Many bicycle parts are brazed, and while bicycles may seem like toys, a 15 lb bicycle frame can handle a 240-lb rider stomping on the pedals and bounding over cobblestones.)
If you're looking to minimize heat distortion, I'd take a look at silver brazing options -- many silver fillers flow when the base metal has barely reached a dull red glow, less than 1400F.
Reply to
Joshua Putnam

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