Repair crack in Shape-rite crank link (was Opinions on how to repair)
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  1. #1
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    Default Repair crack in Shape-rite crank link (was Opinions on how to repair)

    I have been reviewing my options to repair this piece. It is part of a cast iron rocker arm to a Shape-rite shaper. I have never welded and dont have a welder so that is out. Other options include jb weld, brazing and pinning such as with the lock-n-stitch products. Anything I am missing? how would you guys go about this?

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    Grind back a vee groove on either side of the crack and fill that vee groove with braze.

    Or remanufacture the piece out of steel.

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    Take it to someone that can weld/braze cast iron, or make another. Without knowing how that is used, would it be possible to replace that piece with a large link of drive chain?

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    I second the grinding a vee and brazing approach - probably last you the rest of your life.

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    TIG with pure nickle. Keep it cold as possible and bury it in welding blankets for the night to cool

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    I'd also vee it and braze it. If you have a lathe turn a carbon plug for the hole before you braze it. The plug will keep the braze from getting into the bore and it will not stick to the carbon.

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    Quote Originally Posted by kubiack View Post
    I'd also vee it and braze it. If you have a lathe turn a carbon plug for the hole before you braze it. The plug will keep the braze from getting into the bore and it will not stick to the carbon.
    As in carbon welding plate? where would I get carbon?

    Looks like brazing method is most popular. I have considered just making one from steel and it may come to that if i botch this up (i will take dimensions before I attempt anything). Everything I have read implies that cast iron is sensitive to heating and sudden cooling. Thinking through how I would do this, I would have to braze one side, flip it and braze the other side as the crack runs on both sides of the set screw. That reheating wouldn't be a concern would it?

    That set screw is not critical. I can move it even to the other ear that is not cracked. Is there nothing that could be used in the bore to keep the halves together?
    Thanks for the thoughts on this.

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    My local welding shop keeps Arcair carbon rods in stock in various sizes.

    Arcair Carbon Rods

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    Quote Originally Posted by kubiack View Post
    My local welding shop keeps Arcair carbon rods in stock in various sizes.

    Arcair Carbon Rods
    Ah guess i would have known that if I had ever welded. Thanks.

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    In regards to heat: I've had decent luck brazing cast iron with a decent sized rose-bud rather than a small tip. If the material can take the heat, don't be afraid to heat up a large portion of the part rather than just a little bitty spot. From my experience, that's where cracking really becomes an issue, not so much with how much heat is there but with how evenly it is dispersed and how quickly it dissipates. The heat will help clean the break and let the filler rod really soak into it rather than just adding a ball on the surface. However at this point the other risk is actually melting the iron but as long as you only get it hot enough for the filler to soak in then move on, you should be safe. The complexity of the part will also play into how stable it cools, but that part looks simple enough to just leave it out in the open to cool.

    We have a box of Lye in the welding area just for cooling welded parts. If it's something we're concerned about cracking, we'll pack it in there and it will still be too hot to touch 12 hours later.

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    Quote Originally Posted by M.B. Naegle View Post
    We have a box of Lye in the welding area just for cooling welded parts. If it's something we're concerned about cracking, we'll pack it in there and it will still be too hot to touch 12 hours later.
    Lye or Lime?

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    I would make a new link from steel.

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    You can safely braze the crack. It is an unconstrained crack and it will not crack again.

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    Quote Originally Posted by Dumpster_diving View Post
    Grind back a vee groove on either side of the crack and fill that vee groove with braze.

    Or remanufacture the piece out of steel.
    + another on that - if the weld doesn't work you have another bite at the cherry.

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    I had a problem getting the braze to wet out on CI repair, I found going over it with a needle gun after veeing out made the difference between success and utter failure, sposed to break up the graphite, or something like that.

    Cheers
    D

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    Quote Originally Posted by Demon73 View Post
    I had a problem getting the braze to wet out on CI repair, I found going over it with a needle gun after veeing out made the difference between success and utter failure, sposed to break up the graphite, or something like that.

    Cheers
    D
    Interesting thought that one. I have done a lot of cast iron brazing. I can see how your remedy would work and why. The graphite in cast iron "smears" as it is ground away. You're establishing "bare iron" by doing the needling.

    Joe in NH

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    McMaster-Carr

    McMaster stocks carbon rods.

    I would grind and braze or use a nickel electrode and weld.

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    Adam,

    Quite a while back I purchased a Shape-Rite from another PM member who happened to be local (I live in a machinery desert). Mine appears to have been used in production, was crashed sometime in its life, and has a brazed tool head slide repair that seems quite strong.

    Parts for these are pure unobtainum, BUT, at the moment eBay seller "kwktools" (no affiliation with me) has several Shape-Rite parts listed (door, ram clamp handle, saddle). I purchased a ram stroke pointer from him (mine had the tip broken off) and the transaction went smooth, meaning reasonable price, shipping was fast and the item was as described.

    This particular part isn't listed, but I think it would be worth your time to contact him through eBay and ask if he has the rocker arm. From what I can tell, he is parting out a Model B.

    Here's a link to his currently listed items:
    https://www.ebay.com/sch/kwktools/m....p2047675.l2562

    By the way, do you have the later "Model B", or, like mine, the earlier "HY DUTY". Both are 8" stroke.

    Good Luck,

    Tenaya

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    Quote Originally Posted by Joe in NH View Post
    Interesting thought that one. I have done a lot of cast iron brazing. I can see how your remedy would work and why. The graphite in cast iron "smears" as it is ground away. You're establishing "bare iron" by doing the needling.

    Joe in NH
    Thought I was going mad at one point, was sent some info that suggested shot blasting, I figured the needle gun wasnt a mile away from that so gave it a go, thankfully it worked.
    Heres the trip.

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    Quote Originally Posted by dalmatiangirl61 View Post
    Lye or Lime?
    Lime, sorry

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