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I Forge Iron

Friction caliper fail


51 Papy

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Not a fail but not a success.  First pair attempted.  I had filed the two legs flat and to thickness.  The two washers were filed flat and the same thickness.  I used a 5/16 round for the rivet.  When riveted they froze up. I expected that.  I then stuck them in the fire got them red and worked them so all the faces mated up and then tightened the rivet up.  I did this a couple of times.  Resistance seemed to be about the same through the range I wanted them to open so I lightly set the rivet and let cool.  Needless to say they were either froze solid or did not have enough friction to hold the dividers/calipers in place.  I know I did something wrong just don't know what.  The legs started to get thin and the rivet broke.  They now have a thumb screw going through the two legs and into a backer plate.  They work fine just not what I was hoping for.  Anybody want to tell me what I did wrong?

Thanks

Papy

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Once the frozen joint was loosened up from working hot, I would have let the whole thing cool completely before fine tuning the rivet. You tighten the rivet hot, what happens when it cools? That's right- it shrinks and tightens up. All my friction calipers just need a little cold tappy-tap on the rivet when they loosen up. That should do it for you.

Steve

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Ayup, you messed with it too many times. No biggy, we've all done it. ;)

Stash has the right of it. What causes it to tighten up is the section that has been punched, the arms of the calipers in this case, shrink more than the rivet.  

Frosty The Lucky.

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