Trust my protractor?

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Doug,
Legit question - not jerkin your leg on this one or baiting you and I agree with your statement below about not regretting purchasing Starrett.
I own one, it's the off-the-shelf, $70 square and the certificate says it's accurate to within .002" over the length of the 12" blade. So maybe it is square and maybe it isn't but certainly close enough for my woodworking use.
So the question is - if you care to respond:
If it is off by the full .002" (max allowable error) and I haven't checked it yet, then what would that equate to in degrees from being square (90)? This assumes the blade is .002" wider/narrower at one end, which is possible but probably unlikey.
Bob S.

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.0095 degrees.

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I take it then by the no response Doug, that square really isn't square if its a Starrett. But I won't dog you on this as you did me over the word "must" since I knew what your intent was and I don't have to *prove* I was right...;-)
Bob S.
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Reminds me of an old one:
In this world, there are often two sides to an issue. One is right, the other is wrong. It can be difficult to determine which is which, and we can debate it for some time. In the interest of brevity, I have a simple solution to determine who is right, and who is wrong. I'll take the former, you take the latter. Case is settled.
Michael

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wrote:

9 hours. See my other post in this thread.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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A bit late but I just caught this...
Lesee, a computer geek away from his 'puter 9 hours....nahhhhh.... Withdrawl symptoms start at 4 hrs and are unbearble after six. At 9 hours - you're not breathing anymore so it musta been closer to 8 hours...
Bob S.
wrote:

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wrote:

Yeah, it prolly was more like 7. Couldn't be helped though: time in the shop, then go pick up the kids from school, run one of them over to baseball practice, fix supper, eat supper, prayer service at church with SWMBO, pick up kid from baseball practice... time flies.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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wrote:

Angle of error = arctangent ( 0.002 / 12 ) = 0.00955 degrees
So it's within less than 1/100 degree of perfectly square.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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Well ... close enough. My marking knife would make more of a deviation than that over the 12" length.
Bob S.
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well, I'm glad you included the Incra, as that's MY "guaranteed square". 'twas a X-mas gift that I ask for when folks asked for ideas. I got the 5" one so that I can place it next to the BS blade to set the table perpendicular. Not that that's the only thing I use it for, of course.
dave
Doug Miller wrote: If the

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and Starrett; they're both as close to dead-on perfect as I need them to be. I found the Starrett combination square preferable because (a) I needed an accurate, easy-to-read rule as well, (b) it combines accurate 90 and 45 degree angles in one tool, and (c) it's cheaper than buying an Incra 90 *and* an Incra 45 *and* a rule.
-- Regards, Doug Miller (alphageek-at-milmac-dot-com)
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Doug, I've got one of the worlds LEAST accurate combo squares; a Stanley. I should probably toss it into the recycle bin. I sure as heck won't use it on a WW project. It's a LITTLE less accurate than 0.00955 degrees! :)
dave
Doug Miller wrote:

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Au contraire there Dave. There was an article last year in one of the trades where the Stanley was actually rated very highly - if it's the yellow bodied one. The article also showed how to true and tighten them up. I was surprised at how accurate they said some of the lower cost versions were.
Bob S.

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mine is painted black and is from around the mid 70's.
dave
Bob S. wrote:

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ohhhhhh........well JOAT has some yeller paint I'm sure he'd loan ya....
Bob S.

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Geez, if it isn't square, make it so. I've filed a bit on my "Japanese" combination square so it matches, and ditto some lumps on speedsquares. You talk all the time about fettling planes, why shy from squares?
The first square I can remember, an old metal Stanley from dad's 50's shop is now square, and in use at my house. I have a feeling dad never used it much after the many drops it suffered from me.

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Silvan,
Don't confuse made in the USA with being accurate. There are many POS items made in the USA. The same way there are many highly accurate items not made in the USA.
Use the draw two lines method other have mentioned here. Us a marking knive to get a very thin line and see which one lines up.
About every 6 months or so, I get out all my squares and make sure they still agree. I have a couple of fixed squares that I use for setup in the shop and they get banged around sometimes, So I check them against the square that stay in the toolbox. If everyone agrees, them I'm good. If there is a disagreement, then I use the double line method to find out who got bent.
I also recommend that you check your rulers against each other. I got some hook rules one time that were 1/16" off. Not back unless you plan on doing some fine woodworking, hahaha.
Bernie

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