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Welding cast steel

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Welding cast steel

Postby croshaul » Wed Sep 27, 2017 9:46 am

I have some old Harley panhead rocker arm blocks.These are two piece bearings for the rocker arm.The top being brass and the bottom cast. The fit is gone and I would like to rebuild them if possible.The question is what do I use? I'm thinking silicon bronze might work but I have never used it. I only need a couple of thousandth and will machine the fit. What do you think?
Thanks, Ron
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Re: Welding cast steel

Postby noddybrian » Wed Sep 27, 2017 12:51 pm

I do machine work & welding & my first thoughts are a few thou is not much to build up & machine back - may start getting inclusions or have trouble machining that near the weld / parent metal transition - is it possible to bore over size to allow taking up the slack with a bush or bore oversize to allow more depth of buildup to be sure of machining a good surface ?
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Re: Welding cast steel

Postby croshaul » Wed Sep 27, 2017 7:14 pm

Thanks Noddy, these parts are halved and carry a shaft at about 13/16" and there are no parts that I know of that are oversized. It would be great if there were O.S. shafts and I really don't know why, it would be a reasonable and practical.

Anyway, for now I have to do it this way.
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Re: Welding cast steel

Postby noddybrian » Fri Sep 29, 2017 5:53 pm

OK - I've not seen your exact engine part but speaking in general if you have the facility to machine then if there is sufficient material bore the half blocks out round & bigger then machine an interim bush to the original shaft size to take up the difference - I never heard of oversized rocker shafts either - they are also normally very hard so not easy to replicate - if you need to build the brass half as well as the cast steel you cannot use bronze / tig but this will work fine on the cast - I would personally not try tig at all on something like this if I had to build it up I would oxy / acet braze it - never failed me yet - if this is a common problem on older Harley's then maybe ask around on a Harley forum to see what other solutions people are using ? though I bet if you can wait till others here catch up & respond there are bound to be some fellow tractor owners ! - however you tackle it best of luck & hope you succeed.
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Re: Welding cast steel

Postby croshaul » Fri Sep 29, 2017 10:43 pm

I can build them up with braze, silicon bronze or 70 wire, what I am concerned with is what is a better bearing surface.
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Re: Welding cast steel

Postby noddybrian » Sat Sep 30, 2017 3:10 am

Many rockers have / had brass bushes in so I would say braze should work fine as long as everything is cleaned / fluxed & it takes well - the silicon bronze will puddle with the base metal so machining back to only a few though depth will leave a random blend of steel / bronze that will likely be inconsistent & not that good a bearing surface - ER70 should work if you want to keep with the original design of steel - hopefully some else is going to chime in on this as schedules allow maybe with more insight.
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Re: Welding cast steel

Postby croshaul » Sat Sep 30, 2017 12:04 pm

Thanks Noddy, good reasoning.I was apprehensive about using the ER70 when the base was steel already,but cast I think,I will give the nod to the ER70.Thanks
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Re: Welding cast steel

Postby Kevin_Holbrook » Sat Sep 30, 2017 3:01 pm

contact this guy http://tatromachine.blogspot.com/


he has a lot of weld repair videos on YouTube as well
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Re: Welding cast steel

Postby croshaul » Sat Oct 07, 2017 11:56 am

The recommended way to fix this problem is to split the journal and sand each face on a flat surface and ream to size. I had some that were as much as .010 sloppy,fit is a about a.001. I ended up chucking them in my lathe took a light cut and ran a 7/8" reamer through the journal. Which is the correct way to do it.

When I asked the pro's if there were ever OS shafts made for this, I was treated to a free lesson on how to do it correctly.I guess there really is such a thing as a stupid question!
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Re: Welding cast steel

Postby noddybrian » Sat Oct 07, 2017 3:38 pm

Glad you have it sorted - I don't think it was a dumb question - some engine parts are available in over / under size to take up wear - trying to build that little up & machine back was not really viable but you have now achieved a good result - I'm not sure how easy it is these days to buy but faced with worn bearing fit surfaces such as yours on obsolete engines we often would bore a little oversize to restore round then tin & white metal the cleaned surface & ream & / or hand scrape them to fit.
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