Tin Knocker Stomp Shear Pneumatic Conversion

[tailstock4]

These are some pictures of my pneumatic conversion of a Tin Knocker 1652 shear which I believe is a copy of a Pexto shear. This shear was originally a stomp shear which I got tired of stomping on – especially with 16-gauge steel. I’m sure there have a few of these conversions posted, but I decided to share these pictures because of something I did different on this conversion.

Sometimes on these small shears, pneumatic hydraulic conversions can push the table top out of alignment. This table top sets clearance with the shear blades. To reduce stress on the table top and shear itself I made two towers underneath that the pneumatic cylinders attach to. These are welded to two cross members that attach to the underside of the sheer feed. These are freestanding and not attached to the top in any way. I believe this isolates most of the leverage and force to the lower portion of the sheer. The cylinders are 4”, and the arms are 1” plate steel. The rotating shaft is 2” 1018 cold roll solid.

This shear will easily shear 16-gauge x 48” sheets without much drama or bouncing around. No, I would not recommend it for any kind of production setting, of course. But for fabricating jobs in my shop it works great.

 

[tailstock4]

A few more pictures...

 

[Bondo]

Nice job, always nice having a mechanical vs leg powered machines.

 

[52 Ford]

Looks like a pretty solid conversion. Like Bondo said, nice job!

 

[dkmc]

Looks like it's well thought out. Have you done any force calcs compared to foot operated forces?

 

[tailstock4]

Looks like it's well thought out. Have you done any force calcs compared to foot operated forces?

No, I didn’t do any actual calculations. I knew that the 4” cylinders would work. I found these in an auction, so I got them cheap. I used the longest arm possible given the amount of stroke the cylinders have. I made a heavy cardboard template that was cut out to go over the 2” cold roll. Then I worked out the actual arm length and shape given the space limitations. The two tabs on top of the arms that the turnbuckles are attached to were positioned to attain full stroke of the shear. If anyone is interested in the particulars, I can take measurements.

One of the things I believe that helps this shear work really well in addition to the two cylinder towers is the solid 2” cold roll shaft and the 1” thick arms. This eliminates the twisting affect that the original treadle assembly had as it was only 1 7/8” pipe and 1/2” thick lever arms. When I would jump on the treadle on heavy gauge steel, it would start to shear, run out of inertia, and then I would have to jump again which would misalign the stock and aggravate the twisting situation – problems I’m sure that anyone who has used one of these would be aware of.

Thanks for the nice comments. I hope this helps someone if they decide to make the conversion. It really wasn't that hard to do only taking about two days. Using a gantry helped with the heavy lifting as the shear has to be disassembled some what.