Handling of Precision Squares

[eKretz]

It is pretty common for squares to be a little off in that direction in my experience. The thin cross section there doesn't resist movement due to residual stress or whatever causes it. I know I have several that are a bit off that way that have never been dropped or abused in any other way. They are square in the other direction as long as they are held perpendicular at 90° to the part.

[JoeLee]

Looks like something inadvertently bent it. Hardened steel shouldn’t warp. How would Starrett fix that?

Well, when I called and inquired they quoted me a flat fee of $175 to repair it. I didn't ask how they went about it. If I were to take a guess I would say perhaps they roll the dice..... try to spring it in an arbor press, is that doesn't work I wold have to say they press out the pins, put a new blade in, pres in some new pins and grind it all in. I can't see where that is even feasible considering the time involved.

That blade is not just a straight strip, it's actually a flat square pressed into the base so it will stand straight up. I think there are like three pins along the base.

JL.............

[JRouche]

Well, when I called and inquired they quoted me a flat fee of $175 to repair it. I didn't ask how they went about it. If I were to take a guess I would say perhaps they roll the dice..... try to spring it in an arbor press, is that doesn't work I wold have to say they press out the pins, put a new blade in, pres in some new pins and grind it all in. I can't see where that is even feasible considering the time involved.

That blade is not just a straight strip, it's actually a flat square pressed into the base so it will stand straight up. I think there are like three pins along the base.

JL.............

Yes Sir, yu arew correct. They are pinned in there, from the shop. They are not supposed to be ever unpinned though, ever.

That three foot square is pinnen and I would never think of un-pinning it. To the grinder at US Starrett? Yes, if I cared. I dont care. . It was a one off use for a build. Now its a fuking giant starrett square living in my house.

Dont do that..

I have HF squares that line up just as well. Try not to go overboard. JR

[RSG]

I have a cheap set and the largest one had the same issue with a warped blade over time.

[Stargazer]

I have a cheap set and the largest one had the same issue with a warped blade over time.

I wonder what causes the warping. Maybe it's the way they're pinned? I have a ~100 year old combination square whose blades hasn't warped.

[Stargazer]

It is pretty common for squares to be a little off in that direction in my experience. The thin cross section there doesn't resist movement due to residual stress or whatever causes it. I know I have several that are a bit off that way that have never been dropped or abused in any other way. They are square in the other direction as long as they are held perpendicular at 90° to the part.

Just trying to understand here: How can the square remain within .0001 in the xy axis and be out in the z axis? Wouldn't that warpage introduce a sine error?

[Doozer]

Just trying to understand here: How can the square remain within .0001 in the xy axis and be out in the z axis? Wouldn't that warpage introduce a sine error?

Ever heard of a cylindrical square ? Mind blowing concept for some.
They have warpage in a complete circle !

-D

[eKretz]

Just trying to understand here: How can the square remain within .0001 in the xy axis and be out in the z axis? Wouldn't that warpage introduce a sine error?

Only if the square is not perpendicular to what is being measured. The squares are very rigid in the other direction because of the relatively massive width of the vertical blade compared to its thickness. Think of it this way: set your square up against a vertical surface that is in alignment to the blade so that the base of the square is perpendicular to the surface in the axis that the square is sitting on. Now tilt the square so that the narrow edge lifts on one side. Will the blade stay in alignment with the vertical surface? Yes it will - as long as that base is set perpendicular to the surface it's checking. If it's not you'll see a larger gap form along the blade the further you move it from vertical. The warpage of the blade in that direction works exactly the same way.

[Rich Carlstedt]

I wonder what causes the warping. Maybe it's the way they're pinned? I have a ~100 year old combination square whose blades hasn't warped.

Steel is made as a liquid and when cooled , it solidifies . However , it is not stable and develops "strains" (Stress)
These strains can cause warping as they self relieve or if Stress Relieved by a process.
As the temperature drops the residual austenite changes to a much more stable martensite in the steel. In the process, the steel can move (!)
Let me give you a real life example.
I was in Canada and we slit steel sheets in our production machining operation and we shut down for two weeks at Christmas.
During the shutdown, all Power was lost at the plant when the power lines went down , and the factory temperature dropped 80 degrees
for a few days . When we started up, all our carbide slitter knives broke on one slitter. These were 7 inch diameter knives (20 + ) ($$)
The 5 inch shafts they were mounted on the slitters had warped with the temp drop and cracked all the closely set Knives.
The slitter manufacturer had offered Cryogenic treated shafts , but we did not have them...lesson learned
So the original shafts had never been exposed to "Colder" temps than "room temp" and when the freeze came they moved.
So why did the squares warp ? most likely they became colder in storage than previously experienced .
You young fellows do not know what Detroit did over 50 -100 years ago , They would have all their engine blocks set out side for months to "weather" before
machining them.. it was really an attempt to eliminate warpage by low temp exposure so machining did not create more problems with warped blocks.
Improved casting additives eliminated that problem later

Rich

[Mcgyver]

that post reminds me of one of the site's classics.

https://bbs.homeshopmachinist.net/fo...stress-vs-time

Are we talking indoor temp or out door temp. too funny.

I miss Nick and Lazlo and of course Forrest, those were guys who knew what they were talking about. I think Nick got fired or went off in a huff....but what happened to Lazlo (Robert)? Forrest we don't see much unfortunately but he popped up on PM not too long ago, basically saying i'm 80 and slowing down. Friggin time.

[psomero]

Steel is made as a liquid and when cooled , it solidifies . However , it is not stable and develops "strains" (Stress)
These strains can cause warping as they self relieve or if Stress Relieved by a process.
As the temperature drops the residual austenite changes to a much more stable martensite in the steel. In the process, the steel can move (!)
Let me give you a real life example.
I was in Canada and we slit steel sheets in our production machining operation and we shut down for two weeks at Christmas.
During the shutdown, all Power was lost at the plant when the power lines went down , and the factory temperature dropped 80 degrees
for a few days . When we started up, all our carbide slitter knives broke on one slitter. These were 7 inch diameter knives (20 + ) ($$)
The 5 inch shafts they were mounted on the slitters had warped with the temp drop and cracked all the closely set Knives.
The slitter manufacturer had offered Cryogenic treated shafts , but we did not have them...lesson learned
So the original shafts had never been exposed to "Colder" temps than "room temp" and when the freeze came they moved.
So why did the squares warp ? most likely they became colder in storage than previously experienced .
You young fellows do not know what Detroit did over 50 -100 years ago , They would have all their engine blocks set out side for months to "weather" before
machining them.. it was really an attempt to eliminate warpage by low temp exposure so machining did not create more problems with warped blocks.
Improved casting additives eliminated that problem later

Rich

In my Mechanics of Materials course in college, the prof described it as "stress and strain are like when your wife yells at you" and we were all deeply unsatisfied as this had no correlation to materials theory. Later that year, the department went to fire him and eject him from the building but he barricaded himself in a classroom and stayed holed up for an hour or two before he got bored and left.

I like your explanation better 😆

However, wasn't the reason for the leaving castings out (I've heard it called "seasoning") so that you get multiple temperature swings, rather than just cold?

[Mcgyver]

However, wasn't the reason for the leaving castings out (I've heard it called "seasoning") so that you get multiple temperature swings, rather than just cold?

pretty sure that has been debunked

[George Bulliss]

that post reminds me of one of the site's classics.

https://bbs.homeshopmachinist.net/fo...stress-vs-time

Are we talking indoor temp or out door temp. too funny.

I miss Nick and Lazlo and of course Forrest, those were guys who knew what they were talking about. I think Nick got fired or went off in a huff....but what happened to Lazlo (Robert)? Forrest we don't see much unfortunately but he popped up on PM not too long ago, basically saying i'm 80 and slowing down. Friggin time.

Thanks for the reminder. Just viewing a few of the posts in that thread brought on a headache.

I'm not sure what happened to Lazlo either and was just thinking of him the other day. He had planned to submit a few articles and we often chatted via email, but then he just disappeared.

As to Nick, if I'm remembering correctly, he asked to be banned. He had a very hard time understanding that I had no ability, let alone the desire, to police the entire board to ensure each and every post was accurate – at least, accurate according to his standards. I was inundated with emails and PMs from him and as time went by they got nastier and nastier. I'm pretty good about letting such things roll off but it became a daily distraction and frustration, so even if I'm incorrect and he didn't ask, his days were numbered. He had a good number of supporters and I know we lost a few people over my banning him.

[Mcgyver]

yeah, i liked him mostly, but there was no possibility of any way other than his.

sorry about that George....take a couple of Tylenol and send me the bill

[J Tiers]

pretty sure that has been debunked

Yes, someone linked an article here a number of years ago. Looks like the paper was linked in the linked thread, but I cannot access it, repeated "problem loading page".

It was not that it did not work, it does, at least to an extent. But the temperature swings were not sufficient to do much. Something like a 10% reduction in stresses sticks in my mind. Cryogenic treatment gets much colder, and does a bit more, but while it works a little better, it was also not really that effective, as I recall.

I expect the idea was that the colder temps would be enough to get the material to exceed its elastic limit, on the "cold increases internal stresses" theory. If so, cryogenic temps would be better at that.