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Machining fix for apparent misalignment in old stomp shear

JasonPAtkins

Hot Rolled
Joined
Sep 30, 2010
Location
Guinea-Bissau, West Africa
Hey all,
This happened a while ago and my shop is open-windowed in dusty west Africa, don't let the dust and cobwebs distract from the question. I'm building a new shop that will be closed so it can stay a lot cleaner, which means I'm not spending as much time in this one, hence the cobwebs.

One of my less experienced guys was using my old pexto gap shear, which is an awesome machine and never given me any trouble. However, while he was using it one of the cast holddown arms broke. I assumed operator error (maybe he jumped on the pedal before snugging the holddown firm or something). So I machined a new one.

However, when I tried to install it I realized that the arms are both hanging crooked, which I think caused the stress that snapped the casting. The two arms are pulled toward the center of the shear by the points where they attach to the holddown.
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So it seems like the two handles need to be pulled together a bit where they attach to the top round rod. However, I question that diagnosis because I presume they're pinned by a dowel pin whose bore on the round rod has been in the same location for 60 years since the thing was made. Am I missing something here?

I initially thought to loosen the collar on the round rod and shift it left or right, but that would only help if they were skewed in the same direction. That's not the case though, the two connecting rods are pigeon-toed.
 
I thought those had one “arm” and multiple fingers from two hands? The cams have sloppy linkage to allow misalignment.
 
I thought those had one “arm” and multiple fingers from two hands? The cams have sloppy linkage to allow misalignment.
The cam to the connecting rod linkage is sloppy, yes. It's not sloppy enough, however, as the dowel pin that connects the link arms to the holddown can't both be inserted at once, and this lateral force is precisely what broke the eye off of the original cast connector causing me to machine a new one, so clearly it's not a new problem.
 








 
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