I just picked up a used DiAcro 12" shear. It's in pretty good condition, with a little surface rust. The one thing that has me concerned (and puzzled) is that the "apron" in front of the blades is bowed up in the middle. This is the platform that the sheet metal sits on as you feed the stock into the cutting area. There is a ~1" wide section before you get to the blades that's part of the casting, but the main work area in front is a piece of plate steel (probably cold rolled) about 16" wide by about 10" deep. It's held down on each side by a 1/4-20 flathead screw.
This piece bows up about 50 thou a little to the right of center, so there is a step down to the level of the casting & fixed blade. I haven't had time to check if it's bowed across the full depth from front to back or just towards the front edge. There's no obvious signs that the thing was dropped on anything, but it may be that someone picked it up on a fork lift by the underside of the plate or something. The forces required to bend the plate must have been substantial, and I'm surprised the two screws weren't damaged.
The step where the plate meets the casting will mar things when metal is clamped by the hold down system, so I want to flatten the plate out. My first guess is to support the side edges with wood, place a block underneath so it doesn't deflect to far, and then start hopping up & down on it. If I can get it to bend at all, I figure I can tune the deflection by adjusting the thickness of the block in the middle.
Does anyone have any idea how much force it would take to bend a plate like this? Am I likely to be able to flatten this out as described, or is there a better approach? I'd actually like to overshoot a bit and leave it ever so slightly concave. That way the screws on the ends will pull it down against the casting (there's a lip it's supposed to sit on).
Thanks for any suggestions & comments!
Doug White