Wednesday, April 24, 2013

How to make a TRP (Tension Release Pin)

A while back I was working on a machine that needed a tension release pin.  I can't remember what machine or why it needed a pin.  I think, actually, that the machine had a pin, but I wanted one a little bit longer.

I had some small nails that looked to be just about the right size.  So I got out the  nippers and cut one to size.  It worked quite well.

Recently, a reader emailed me about the tension release pin on a Singer 301.  I promised that I would cut  a TRP to the correct size and send it off in the USPS.  I finally got to it today.

I took the tension assembly out of the Singer 301A long bed that I bought last spring.  I had performed some aluminum rot surgery on it then and  never really finished that job.  I have yet to prime and paint it.  But the surgery was apparently a success.  No evidence of further corrosion.  At least on this spot.  Since the weather is going to be nice this weekend I think that I will finish this job and prime and paint the repairs.  Don't know why I didn't do it in the first place...

TRPs have a darling little nub on one end that prevents the pin from falling out of the tension assembly.  I cannot replicate that nub, so when using a custom made TRP, one must be careful not to let it fall out.

The TRP is 1 1/8 inches long.

The nail is 1 1/2 inches long
I cut off the sharp end and filed it down so that is was smooth.  Then I lined up the two pins next to each other in the  nippers

 And cut it to size.

I stuck the nippers and nail inside a large yogurt container when I cut the nail.  That prevented the nail and cut piece from ricocheting around the shop.  I did not do that when I cut off the sharp point.  Luckily the nail didn't fly far.  Who knows where that little pointed sharp piece is.

I did have to cut the nail again because the first time I didn't get it short enough.  Better that than the other way, eh?  

This pin will fall out of the tension assembly, unfortunately.  I guess one could put a tiny little dollop of JB Weld on one end to prevent that.  Hmmm may have to try that.  


  1. If you use common nails (softest metal) you can take a hammer and place the nail end on some flat thick steel surface (I used the head of a 5 lb pounding maul), you can hammer the the end of the pin (like a blacksmith) to make the stop-flange. It's easy - takes about 30 seconds.

  2. In reference to my former comment: I would make the stop-flange end first; do a little clipping and sanding (if necessary) and then measure to the flat end before making the final clip to length.

  3. Awesome, I am going to try that when I get my hands on a pair of nippers. As for replicating the nub, do you have a vise? I'm wondering if you can smush (technical term) the nail head flat, and if that would work well enough to hold the pin in place.

    - Rain

    1. Another good idea. I think I will try that.

  4. You guys make me think of my grandma; Use it up, wear it out, make it do, or do with out! Good job! Way to make do with what you've got!!! Good ole brain power!

  5. Thanks for this tip. I have a monster vise. I'll try pinching one end of the nail to the proper flatness. Regards, Ron