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View Full Version : rotary manual shear



darryl
05-13-2013, 01:15 AM
Now and then I have need to cut some thin sheet into fairly round discs. A bit more elegant than hand shears might be a rotary shear, so having seen one a couple months ago, I bit the bullet a few days ago and brought one home.

http://img.photobucket.com/albums/v136/heinrich/rotaryshear_zps383c1720.jpg (http://smg.photobucket.com/user/heinrich/media/rotaryshear_zps383c1720.jpg.html)

As expected, it's a piece of crap- probably a bit worse than I expected actually. My plan was to replace the lever with a crank, which will be easy enough, then add a bit of a table to one side that I can set a pivot point into. I'd drill a hole in the piece of sheet, set a bolt through it, then crank the shear around until a round disc emerges.

So- I take it all apart of course, to check it out. The serrated cutter disc is mounted on a fairly decent sized hub in the top part of the tool. Aside from the ratchet handle to turn the disc, it seems good enough that I can leave it as is for now. The bottom cutter disc has about the crudest setup you can imagine- it's crooked to start with, and looks like it will break about the second time I use it. I want to make an improvement here.

It seems that when there's enough pressure between the two discs so they remain in contact when shearing, there's too much friction and the bottom disc doesn't want to turn. I'm thinking to mount the disc on a shaft with bearings, then give that a means of raising and lowering the disc. There would be a fair amount of side pressure on the bearings, but well within axial ratings for bearings that would actually fit in the room I have for them.

Maybe that's too much work for a piece of crap tool, but it would surely make it work better- no?