Bent Square Fix?

darita · Apr 21, 2013

I just bought an 18" Starrett square that has a very slight bend in the blade. It's not a kink in the metal, just a bend. Is there a way to bend it back flat without messing it up? Is it something I can do at home or does it need to be taken to a machine shop? It still measures square, but I hate knowing that the bend is there, although you can't really see it unless you look for it. By the way, I use this square to set up my woodworking machines. Thanks for the help and thanks for having me in this forum.

RDL · Apr 21, 2013

"slight bend" is not the best information. It would better to volunteer more information such as a picture, measurements, describe if the length of the bend ...

What tools to you have to fix it? Do you have a press in which you can measure the displacement? Only an experienced person would freehand this. A lesser experienced person should apply forces in "little doses" and incrementally. The placement of the two holding points will depend on the bend. Some may even advise to shrink the bulged side but I find high heat risky.

AdamC · Apr 22, 2013

No, you can't fix it. You might be able to straighten it some, but it probably is out of square now and will be more or less so after you screw with it. It may or may not be good enough for what you are using it for so I'd hesitate to suggest it is trash, or must be reground.

The key to buying second hand gear is that you need a way to determine what you bought. You need master tools. If its a no 20, I know how expensive these tools are new. So I feel for you.

My recommendation is to get another square that you can trust, and use that only to inspect the squares you use. Funny how often I hear about people saying such and such is good enough for woodworking. If you want to make nice square projects no little or no gaps, you need pretty close tolerances.

darita · Apr 22, 2013

AdamC said:
No, you can't fix it. You might be able to straighten it some, but it probably is out of square now and will be more or less so after you screw with it. It may or may not be good enough for what you are using it for so I'd hesitate to suggest it is trash, or must be reground.

The key to buying second hand gear is that you need a way to determine what you bought. You need master tools. If its a no 20, I know how expensive these tools are new. So I feel for you.

My recommendation is to get another square that you can trust, and use that only to inspect the squares you use. Funny how often I hear about people saying such and such is good enough for woodworking. If you want to make nice square projects no little or no gaps, you need pretty close tolerances.

Thanks for the reply, Adam. Right now, I'm comparing to a good 24" Starrett and it looks pretty good. It's as close to dead on as my untrained eye can see and that's good enough for me. I just want to know the best way to straighten this thing without throwing it out of square.
I hear the same thing from many woodworkers who don't believe precision is that important in woodworking machines and I don't understand that. The error you take out of your machines, the less error is transferred to the wood. Yes, wood moves, but I'd rather the wood move from square, rather than from out of square. I can't afford new measuring equipment, but I can afford a few essential, used squares.

allloutmx · Apr 22, 2013

grind it back to square

AdamC · Apr 22, 2013

darita said:
Right now, I'm comparing to a good 24" Starrett and it looks pretty good. It's as close to dead on as my untrained eye can see and that's good enough for me.

I think you are better off leaving it alone. And I realize how much you might want to "fix" it if it is only off a small amount. But please do bear in mind, if it's the square I'm thinking of, it was originally good within .0001"/6". For it to remain good, the bend would have to be PERFECTLY perpendicular to the beam length. Let's say it's close to that since you aren't detecting a big problem with your 24". The fix would have to move it back exactly perpendicular. You probably won't get it to move BACK (along the same axis as the original bend), just due to work hardening alone.

So (hand) forming and regrinding is the right fix, but I don't know of too many grinders that can achieve the original spec accuracy. I'd be be inclined to spot it from calibrated granite and bring it back by hand.

darita · Apr 22, 2013

AdamC said:
I think you are better off leaving it alone. And I realize how much you might want to "fix" it if it is only off a small amount. But please do bear in mind, if it's the square I'm thinking of, it was originally good within .0001"/6". For it to remain good, the bend would have to be PERFECTLY perpendicular to the beam length. Let's say it's close to that since you aren't detecting a big problem with your 24". The fix would have to move it back exactly perpendicular. You probably won't get it to move BACK (along the same axis as the original bend), just due to work hardening alone.

So (hand) forming and regrinding is the right fix, but I don't know of too many grinders that can achieve the original spec accuracy. I'd be be inclined to spot it from calibrated granite and bring it back by hand.

Can any machinist do this or do I have to go to a specialist?

MikeS-54 · Apr 23, 2013

OP, a picture is worth a thousand words.

I get the impression that the bend is in the thin direction of the blade and has nothing to do with being out of square.

darita · Apr 23, 2013

Here's the best pic I could get. Hope you can see it. The bend is just about dead center. I can't see how it got there, as there is no other damage to the square.

allloutmx · Apr 23, 2013

darita said:
Can any machinist do this or do I have to go to a specialist?

It sounds to me like you want it pretty good, so i would definitly give it to a grinding specialist. When i first started here i bought a cheap 3pc square set...i handed it off to our senior grinder to do his thing. ive got a few thousand hours of grind expierience and to get something that thin and long back to square..yowch. measuring squareness of a square isnt easy in itself. most accurate way we use is our light squares but even then...its as best as you can see. dont get me wrong, its not impossible, but to fix it right, id have it ground back by a specialist.

allloutmx · Apr 23, 2013

correction...its bent the wrong way from what i was thinking..you might be able to peen it back to close then regrind... thats a bummer

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