Engineer's square

Bill wrote:

I found this to be one of the most useful measuring/marking tools I've acquired--I use it constantly.
http://www.leevalley.com/wood/page.aspx?c=2&pD279&cat=1,42936
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On Mon, 23 Nov 2009 21:18:25 -0500, Bill wrote:

I think that's the same set I bought at Woodcraft. The precision of (IIRC) 0.0006" is marked on the blades, but no indication of whether that's overall or per inch. In either case, I set the 6" up against a pricey machinists square on a flat surface and there was absolutely no light between the blades. I'm happy.
--
Intelligence is an experiment that failed - G. B. Shaw

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If it only says .0006, it's per inch, not total error.
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Larry Blanchard wrote:

The precision should be per inch.
While they are on the lower end of accuracy for squares used for setting up metal cutting tools, their precision goes beyond anything that is likely to be detectable in woodworking. Face it, there's nothing magic about machining two pieces of steel flat and sticking them together at right angles--they can do that as well in India or China as they do in the US and Japan and the EU.
The place to spend the bucks is with a combination square--there the cheap ones usually aren't square out of the box and if they are they don't stay square very long--since they have moving parts, maintaining precision is more difficult than for something that is permanently welded/brazed. I finally spent the bucks for a Starrett and I'm glad I did. Browne & Sharpe and Mitutoyo also make good ones.
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On Tue, 24 Nov 2009 06:56:42 -0500, J. Clarke wrote:

I've got one of the first squares from Stanley Rule and Level Company. They put the handle and the blade in a jig and poured molten metal into a matching set of holes. After all these years, it's still right on!
--
Intelligence is an experiment that failed - G. B. Shaw

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Accuracy of that double square is stated as " better than 0.001" per inch"
http://www.leevalley.com/wood/page.aspx?c=2&pD279&cat=1,42936
Bob S.
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BobS wrote:

A few years ago, long before I found this forum, I bought two carpenter's squares, 24" and 8", believing that I was starting my woodworking tool collection. I assume they may be good for deciding flatness and maybe cutting some square (replacement) pieces of drywall and as a replacement for a steel rule (?). I anticipated using them as a try square on wood, but from what I've read here they don't make the grade.. Does anyone here use carpenters squares for anything (besides stairways and roofs)? Probably precise enough to use on outdoor furniture, huh--or better than that?
Bill
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Bill wrote:

I've found engineer squares quite useful for machine setup. I carry a 2" one in my shop apron for quick double-checks on various settings such as jointer fence, etc.

Probably not so much. A good tri-square (combination square) would work better

Probably would recommend one of them first or in combination with the engineers squares

They wouldn't be engineers squares if they were graduated.
Dropping them is definitely not a good thing.

IMO, the set of engineer squares, with a combination square, and a good straight-edge are a good start.

--

There is never a situation where having more rounds is a disadvantage

Rob Leatham
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Bill wrote:

I'm cheap. For machine set up I use an inexpensive plastic drafting triangles purchased at one of the local office supply places. I find them more than adequate for woodworking.
--
Jack Novak
Buffalo, NY - USA
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Nova wrote:

And you never risk dulling a tooth or blade?
--

-MIKE-

"Playing is not something I do at night, it's my function in life"
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You'll never regret buying a good square. However, they're only good 'til the first drop, so consider how (and where) you'll be using it. For the purposes you describe, I don't think you can go wrong with the Groz. If you're still not sure, buy the Groz, take it to your shop and see how much or if it's off square, and if that doesn't meet with your minimum requirements, take it back and tell them it's not square and step up to the Starett.
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Joe wrote:

The only "test" I can think of is the one I learned for a carpenter's square: You use the square to draw a perpendicular line to the edge of a board, then you flip the square over and draw another line. The lines should be the same or parallel. Repeat several times for higher confidence. How does that test measure-up here???
Bill
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On 11/24/2009 01:46 PM, Bill wrote:

If you don't already have a known-good square, then that test works. You need to make sure that the edge you're referencing the square against is straight. If you're using a wooden surface, a knife will give a finer line than a pencil.
If you've got a known-good square (a drafting triangle works fine) then take it and the one being tested and place them both facing each other against a known-straight edge. Hold it up against a light and see how big the gap (if any) is between the two blades.
Chris
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wrote in message

that's the test I would use, but with a very sharp marking knife instead of a pencil.
jc
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wrote:

I use my Starrett combination square. It's a little bit better than using an index card.
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I found that a nice 4" double square is a pleasure to use, and very handy. They usually go for $40, but I've seen sales for $20.
I use that more than a fixed engineering square.
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message writes:

If you wish to check that your TS blade is vertical, for instance, do you just use the base of the double square? It would appear that the base has the potential to have more "integrity" than the angle it forms with the rule. I like that it is graduated--seems very usable indeed.
My thanks to everyone who has helped with this thread!
Bill
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"Bill" wrote:

No tools required, just a piece of scrap and a miter gage.
Lew
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writes:

If the angle it forms with the rule is not square, return it or throw it away. If I were in your position, I would buy a GOOD combination square a they are very versatile. You won't find a good one at Home Depot. I would suggest Starrett (though I have a Mititoyo). There are several top end combo squares that are as accurate as a Starrett but Starrett will, at a very reasonable charge, fix it if you damage it. Expect to pay $75 to $100 for it. Seems expensive but well worth it. The cheap ones that you find at your local home center are near useless. When setting up a machine, you need accuracy. If the machine is not set up right, it will transfer this inaccuracy to the work piece. After making many pieces, all the errors will ad up to the point things won't fit. This is particularly bad for the less experienced as they may not know what the problem is, They will likely think it is something they're doing wrong when it really is a badly set up machine. You often here people say within 1/64 is close enough for woodwork. For some things it is but for many things, 1/64 off might as well be a mile.
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"CW" wrote:

Just curious.
Since most of the above applies to metal working machinery, how does it transfer to wood working tolerances?
You can machine a metal piece +\- 0.001" and come back a month later and find the piece to still be within spec assuming ambient temperatures are similar.
Machine a piece of wood to the same +\- 0.001" in the morning and it will be out of spec in the afternoon.
Basic reason any material that gets machined, gets glued up the same day, at least in my boat yard.
IMHO, expecting to maintain wood tolerances greater than +\-1/64" over any length of time is a stretch.
Lew
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