Engineer's squares

[cwsmith]

Mac,

I think you'll find the consensus on framing squares being that an accurate one is a rare bird indeed. Everything I see today is aluminum. I don't know how the old steel ones are.

CWS

[bigsteel15]

I just checked the (2) $20 Maximum tri-squares that I have.
they state right on them...accuracy = 0.1/100"
I assumed that meant they would be no more than 1 thou out over the 8" length.
Well one of them is off, becasue when I sqaure them to each other, outside to inside, there is a gap of about 1/32" at the end.

[LCHIEN]

I just checked the (2) $20 Maximum tri-squares that I have.
they state right on them...accuracy = 0.1/100"
I assumed that meant they would be no more than 1 thou out over the 8" length.
Well one of them is off, becasue when I sqaure them to each other, outside to inside, there is a gap of about 1/32" at the end.

Ha, what that means is that there is up to 0.100 inches error per hundred inches of rule so over 8" each could have .0125" off 90°.
So if each was off by .0125 in the same direction it would be a total error of .025" when you "square them off against each other"
which is between, but somewhere closer to 1/32" (.031) than 1/64th (.016).

Sorry but that's the way I interpret it. resolution is specified as a small number but Accuracy is usually specified as being over a certain range., in this case 100".

[lcm1947]

Hmmm, boy this is a problem if you can't buy an accurate framing square. So what do you guys do to setup the TS?

[bigsteel15]

Ha, what that means is that there is up to 0.100 inches error per hundred inches of rule so over 8" each could have .0125" off 90°.
So if each was off by .0125 in the same direction it would be a total error of .025" when you "square them off against each other"
which is between, but somewhere closer to 1/32" (.031) than 1/64th (.016).

Sorry but that's the way I interpret it. resolution is specified as a small number but Accuracy is usually specified as being over a certain range., in this case 100".

Well I guess I'll keep the LV squares on my wish list then.
These are still the most accurate I have right now though.
My birthday is next week (big 4-0) and LOML and parents both have my wishlist via e-mail. Although I'm not supposed to know my parents are making the 12 hour trip to be here for it.

EDIT: So which ones?
http://www.leevalley.com/wood/page.a...99&cat=1,42936
or
http://www.leevalley.com/wood/page.a...01&cat=1,42936

[Tom Miller]

EDIT: So which ones?
http://www.leevalley.com/wood/page.a...99&cat=1,42936
or
http://www.leevalley.com/wood/page.a...01&cat=1,42936

I can highly recommend the second ones (all steel). I have four, and have tested all possible pairings against each other on my jointer bed. No light visible along the blades.

Regards,
Tom

[LCHIEN]

Well I guess I'll keep the LV squares on my wish list then.
These are still the most accurate I have right now though.
My birthday is next week (big 4-0) and LOML and parents both have my wishlist via e-mail. Although I'm not supposed to know my parents are making the 12 hour trip to be here for it.

EDIT: So which ones?
http://www.leevalley.com/wood/page.a...99&cat=1,42936
or
http://www.leevalley.com/wood/page.a...01&cat=1,42936

They both claim squareness to the tune of .001" per inch which is EXACTLY the same spec as the ones you have that you don't like...
that is, .001"/1.00" is the same as .1"/100"

However, if they have good manufacturing control, then most of them should be much better than that.

[mdutch]

...Well one day I broke down and bought a Starrett combination square after holding it and feeling how nicely it slid and locked into position. Well using that new square to test my other ones I was amazed to find that my others were not square at all! The Craftsmen were not at 90 degrees and the Stanley would lock at different degrees except true 90 all along its width.

Same here! I thought it was me.
I'm a bit concerned about the longevity of the Starrett's accuracy, but when the Rockler guy showed me how much variance there is between three $30-70 "engineers" squares he took off the shelf, I was convinced that the Starrett is DANG accurate.

Even had him snap and unsnap it to different angles to make sure it was coming back to the same spot. It was dead-on.

[Tom Miller]

Ha, what that means is that there is up to 0.100 inches error per hundred inches of rule so over 8" each could have .0125" off 90°.

Wouldn't that be 0.008" over 8"?

Regards,
Tom

[Tom Miller]

Hmmm, boy this is a problem if you can't buy an accurate framing square. So what do you guys do to setup the TS?

Framing squares can be made accurate, though I've never done it. Using a punch and a hammer, you whack it near the inside of the vertex to open it up, or at the outside of the vertex to close it down.

I have no idea how much error you can expect to correct by this technique. But given the use of the device, you could argue that anything less than 1/16" over the length would mean the technique is of no practical use.

Regards,
Tom

[LCHIEN]

mea culpa

Wouldn't that be 0.008" over 8"?

Regards,
Tom

GULP! Why yes, it would.

I guess i divided .1 by 8
instead of 8 x .1/100

well in that case, 1/32" is way out.... should have been a max of 2 x .008 = .016 or about 1/64th for two errors.

[bigsteel15]

I love a good ribbing.

Ha, Loring got one wrong.
Put that in your steel pinky ring and smoke it...LOL
I love it when engineers are wrong. I catch my boss (petroleum eng.) in a moment of confusion every once in awhile. Feels good.

You did contradict yourself in your last post Loring.
In the original "HA" post, you multiplied the 0.1" by 12.5 instead of dividing.

That all said, it still seems that my existing try squares are not in the tolerance they claim.
Good thing I didn't pay $20 for them. $10 on sale (what should I expect, except that they be as advertised).
I'll get out the feeler gauges and check it out tonight. Shouldn't have more than 0.016 space.
Maybe I should use my 1-2-3 blocks from LV. they should be **** close to perfect, no?

[Tom Miller]

I love it when engineers are wrong.

Ahhh, but if he's assisted by a fellow engineer, then we come out even.


It's in the rule book.



I can show you if you don't believe me.


And just so this post isn't completely without merit, I found my LV squares to be much better than the spec'ed 0.001"/1".

Regards,
Tom

[LCHIEN]

...
I love it when engineers are wrong. I catch my boss (petroleum eng.) in a moment of confusion every once in awhile. Feels good.

...

One of my professors always said (when an engineering student made an excuse for a mistake) "Bridges will fall, planes will crash..."

[lcm1947]

Well ,I for one don't find it amusing when engineers are wrong. I find it disturbing. Anyway, to get back to the point - not all is lost. I purchased a 12" & 24" rafters/framers squares at Lowes and they are both dead on using the test posted earlier. Course I used a #7 mechanical pencil in the test but that's pretty darn dead on to me. You might have to try several before locating a good one but it can be done. I am so pleased with myself. The 25" was a black one and there is no manufacturers name on it anywhere but the 12" was the regular silver job made by Johnson. Now if I can just locate a good 12" sliding square for less then a weeks paycheck I will be all set. I am also looking at some of the Incra's stuff like the 12" T-square but not sure if I'll purchase it yet. $35.oo is still a lot in my way of thinking plus I really would prefer a 24 to 36" T-square but just may have to build one as I don't think anybody makes even a 24" one. RATS! But just in case someone knows of some outfit making them I'd sure appreciate hearing about it.