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Proof of Concept for S-Cam repair

This was my first try at adding "bearing material" to a S-Cam journal. It's a super epoxy with a high ceramic content. 

It's very tough on cutting tools. And needs good prepping, which I didn't do.

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S-Cam Repair

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Photo Information for Proof of Concept for S-Cam repair

Taken with OLYMPUS IMAGING CORP. u1010,S1010

  • 6.6 mm
  • 1/30
  • f f/3.5
  • ISO 200
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I used to grind crankshafts and considered having it welded and then ground. If it was someone else's money, I might. But, there are two journals on each S-cam and a lot of heat is generated during welding journals. My biggest concern with welding and then grinding the journals is that I don't know anything about the hardening and heat treating used on the S-cams. 

There was several ways I could have "repaired" the s-cams. The epoxy approach was Plan A. It was the least destructive to the base material. The epoxy was $45 and claims to be suitable for repairing this type of bearing. If this stuff flakes off I can always get more aggressive/destructive with grinding then sleeve it - still no loss of base "hardening". The last and most aggressive/destructive of the original part is grinding, welding, then grinding again.

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You could weld it up and grind it  back to size then send it for heat treat if the epoxy doesn't work out.

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I like your thread and photos.  I have a '64 B61T with thread damage where the S-cam shaft and brake chamber mounting bracket attaches to the axle.  The right side has one bolt in the bracket and a weld to hold the bracket to the axle.  The left side has two bolts and that is it.  The bracket is pulled away from the axle where the bolt is missing.  I bought a new 5/8"-18 x 1-1/2" bolt, that matches what's on the left side, to try.  The bolt enters the hole but the threads are getting knocked down badly.  What is the thread count of a stock bolt?  Is it the fine thread or course thread?

 

rightside_scam_bracket_2.JPG

rightside_scam_bracket.JPG

rightside_scam_bracket_1.JPG

rightside_scam_bracke2.JPG

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My chamber support bracket has three flanges. I added some cracked-weld pics: S-Cam Repair & Cracked welds

5/8"-18 is what's on my axle tubes - the threads were badly butchered. I still haven't found a 5/8"-18 thread chaser - 9/16" seems to be the biggest.

  • A thread-chaser is not, and never will be, a tap
  • A thread-chaser re-forms the existing threads
  • Dulling a tap can make it a thread-chaser
    • Use a on a wire-wheel on a bench grinder to dull the tap.
    • Be really, really aggressive in dulling the tap - you want the "dull tap" to re-form the existing threads, not cut new ones.
    • With fine threads, false starting the dull-tap/chaser is easy so take your time 

If the hole is beyond saving, there's always helicoil repair - which is a lot easier said than done for a 5/8" bolt, on really hard/tough steel. Not a job for the biggest 1/2" drill.

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