Flattening 1/4" Steel Plate?

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
Reply to
Gwhite
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Is it this one?
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If it is, it looks like you may be missing a screw that's supposed to hold the plate down in the center. It also looks like, with the exception of the hole for the squaring guide you could probably turn the plate over and bolt it down to take the bow out of it since it would be straightened when it was forced down against that edge you mentioned. The holes may be countersunk too which would pose a bit of a problem though.
If it isn't like that one, go here and see if you can find another manual that fits:
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Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com
"I'm not grown up enough to be so old!"
Reply to
Keith Marshall
I have spent literally thousands of hours with shears. Square up the fence to the blade, maybe reverse the blade for sharpness or true it up yourself. I always liked to set it up to cut 3 layers of newsprint.. Keep it oiled with something close to sewing machine oil. If it has slight nicks just stone them out. Dang if I had a buck for every stoke I laid on hand and stomp shears well I would still be broke, but, at least my knees would still be good. Keep the guard in place if you have one. Fingers are expensive to replace.
Reply to
daniel peterman
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It's the #12 shear shown in the manuals, but there isn't a screw in the middle of the apron. I suspect this is either a design change, or was only present in the 24" model. The plate has countersunk screw holes, which makes inverting it a problem. In addition, the amount of force required to flatten the bowing would be very hard on the screws. I'd still wan to flatten it a bit in any event.
Doug White
Reply to
Doug White
Keywords:
It has a guard/hold down mechanism, which I plan on keeping in place. However, using it with the bent apron will only damage the workpieces even more than without it, so I need to flatten the apron first. I'll keep the newsprint trick in mind.
The Diacro shears had four cutting edges per blade, and I'm hopeful I can find a couple edges left that are still sharp and unrusted.
I've read a couple postings in the Google archives about using a special hammer to flatten things, and also about using a torch to heat & then quench plates to flatten them. That sounds like a possibility, but I'm not sure my Mapp gas torch is up to the task. Another thread suggested shimming it up and then driving over it with a car, which is an option, but a bit hard to control precisely.
Doug White
Reply to
Doug White
It may be that your shear is just cold, I always found they need to reach a steady temp to really be good. You can block up the end of the holddown with a bit of pine. You really don't need it there except to keep your fingers out of harm's way.
Reply to
daniel peterman

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