Engineer's squares

[jnesmith]

So for you guys singing the praises of drafting triangles I just have to ask, how do you know they are square? Is the 90 degrees really 90 degrees the whole length and is the edge flat? What have you checked them with for a baseline or are you just assuming? Not trying to start an argument just curious as it goes back to my point of having something as a baseline to check everything else against.

I guess I don't know. I mail ordered some good quality ones, and have just assumed they are accurate based on all the praise I have read. I haven't had any problems that would indicate they are inaccurate though.

Having said that, I also have 2 engineer squares, a 12" Starrett combo, an Incra "guaranteed" 45 degree square, and a 4" "double square". I use all of them, but love the little double square.

[BobSch]

So for you guys singing the praises of drafting triangles I just have to ask, how do you know they are square? Is the 90 degrees really 90 degrees the whole length and is the edge flat? What have you checked them with for a baseline or are you just assuming? Not trying to start an argument just curious as it goes back to my point of having something as a baseline to check everything else against.

Check this thread http://www.bt3central.com/showthread.php?t=19659 . About halfway down there's a diagram of how to check for squareness. FWIW, I've got three triangles from different manufacturers and NONE of 'em are really square.

[cgallery]

What's your mailing address? I spent 17+ years on a Mayline table, and in that time accumulated a whole drawer full of 'em. Be glad to send you one.

I'll join the chorus of those singing the praises of Starrett squares. I have a 6" Starrett double square that I keep in the front pocket of my nail bags, and it's probably the best single $50 investment in my entire shop.

To what degree are your triangles off?

[BobSch]

The first thing I did when I took my $50 Starrett double square out of the box was check it using this test. Luckily, it passed, with honors.

Luckily? I wouldn't expect anything else from Starrett.

(But I'd still check it...)

[messmaker]

(Okay, not literally. I do have enough triangles, total, to fill at least a small drawer, but only a few of them are inaccurate enough that I learned not to use them.)

Why do you keep an inaccurate drafting triangle? Its like a lock with a lost key;not much good.]

[cgallery]

Luckily? I wouldn't expect anything else from Starrett.

(But I'd still check it...)

Interestingly enough, people I know that work in machine shops don't give Starrett a universal pass. The combination squares are pretty well respected, but some of the other stuff apparently leaves a little to be desired.

Thanks,
Phil

[LarryG]

Phil: I'd have to dig out all my old stuff and check, but I remember one that was off a sixteenth or better over its length (which was probably 8", as that's the size I favored in both 30-60-90 and 45-45-90 triangles). But as Bob says, I don't think I owned any that were PERFECTLY square. My 6" Starrett double square is more accurate than any drafting triangle I ever had.

messmaker: Partly because I use my older triangles as straightedges for X-Acto knife cuts. Partly because I'm an incurable pack rat who cannot bear to throw ANYthing away. (Anyone out there need any 9600 baud modems? VGA video cards? A nice, low mileage, 125 megabyte hard disk? Send me a PM ...)

[BobSch]

Why do you keep an inaccurate drafting triangle? Its like a lock with a lost key;not much good.]

That's for the mooching neighbor who never returns anything, right?

[kwgeorge]

Guys, the point I am trying to make here is that nothing is really a guaranteed 90 degree angle or strait for that mater. So then it becomes a mater of just how much off is the tool and is it livable or even noticeable. In the machining trade strait edges, squares and such are sold to be within a range. Like a strait edge could be sold that they say has a tolerance of .0001” per foot. Normally the more zeros after the decimal point the more money you pay. I have seen strait edges priced in the thousands of dollars. I learned the hard way not to trust what I buy for this purpose without some type of testing else your end results could suffer greatly or just a bit that is allowable. I think anything that you buy or use for tool setup and layout is fine as long as you trust it and have some way to test it. This could be using some mathematical methodology (I leave that to the Loring type guys) or at the very least the owning of one such tool that you have confidence in to test all others against.

Like others though I have issues with the Aluminum squares as they flex and wear out also to really use the ruler section as a guide it really should be hardened steel so it does not bend and flex and damage easily in the shop. Now one I bought not to long ago was from Grizzly and it is cast iron and is pretty darn true when tested against my Starretts;

http://www.grizzly.com/products/g5726

Now Woodcraft sells what I believe to be the same one for $69.99 instead of the Grizzly $26.95

http://www.woodcraft.com/family.aspx?familyid=434

In any case I just think you should have some method of checking tools used for setup and layout rather than assuming you bought something decent. Voice of experience.

Ken

[cwsmith]

Tom Miller,

I was given a set of three, so-called "machinist squares" a few years ago and only the smallest one (about 2", as I recall) seemed accurate. The other two were off about a 1/32 from base to tip. With the largest one being about 5 or 6 inches, I considered it significant. They weren't branded and I imagine they were quite inexpensive. But with that sample, and my satisfaction with drafting triangles, I couldn't see exploring it more.

KWGeorge,

From a drawing point of view, you check a triangle by placing it's base against a straight edge (or parallel, as on my drawing board) and you scribe or draw a vertical line, then flip the triangle over and if the triangle is true, there should be NO variation.

Between 1966 and 1989 I was on the drawing board almost every day using the parallel and triangles to do technical illustrations for some of the biggest companies in the North East. I never took a liking to "drafting machines" for illustration work and preferred using the parallel and triangles. My favorite triangles were made by Dietzgen, but I think they are out of the business now. I have Dietzgen, Post, Alvin and a few odd names. The worst triangles were the C-Thru brand; I see they are still around, so I hope they are improved. I also have a precision set of stainless steel Theo. Altenedor & Sons which were almost $100 a piece, as I recall. Rule 1: Never use the parallel or triangle edge to directly guide a cutting blade! (One slip and you may as well throw it out.)

Since the late 80's, all my illustration work has been done on the computer, so the triangles were wrapped and put away. I've found new use for one or two of them as I progress into woodworking.

CWS

[Tom Miller]

Tom Miller,

I was given a set of three, so-called "machinist squares" a few years ago and only the smallest one (about 2", as I recall) seemed accurate. The other two were off about a 1/32 from base to tip. With the largest one being about 5 or 6 inches, I considered it significant. They weren't branded and I imagine they were quite inexpensive. But with that sample, and my satisfaction with drafting triangles, I couldn't see exploring it more.

I can see why you choose to steer clear of the "inexpensive" machinist squares!

When I decided to give them a try, I chose to buy them from Lee Valley for two reasons. Reason #1: I recall they gave some indication of the accuracy spec, unlike a lot of other vendors. Reason #2: Given their reputation, I felt that their accuracy spec meant something.

If you decide to give 'em another try, I can heartily recommend the Lee Valley ones. But it sounds like you're doin' fine.

Regards,
Tom
(I can just picture some guy sorting machinist squares as they come off the assembly line. "Lee Valley, Lee Valley, Lee Valley, yikes! Harbor Freight! Lee Valley, Lee Valley...") Let the flame wars begin! <ducking and covering>

[gjbivin]

It never ends

The "squareness" test (flipping the square along a straightedge) is certainly the way to test the square, but it depends on the straightness of the straightedge, which is just as problematical as the squareness of the square. I guess you could snap a chalkline and test the straightedge against it to see if it deviates. Or maybe a laser level could be used to guage the edge somehow. A more practical idea is to test the square using both sides of the straightedge or with different straightedges, and compare the results.

[cwsmith]

Gary,

If the straight edge is not straight, then even a good triangle would look like it is off. Then you'd have to check the triangle using another straight edge or at a different spot on the straight edge. But, there is no way you'd ever get a bad triangle to look good, whether the edge was straight, bowed, dipped, etc. Finding a good straight edge is probably a lot easier than finding a perfect square.

CWS

[Thom2]

I guess I'm from a different school of thought

If I have squares that are perfectly accurate, then I have nothing to blame for my mistakes, I like having something to blame

In all seriousness tho', I don't own a starrett yet, but someday I'm sure I will. For now tho', I've got a 4 piece set of "made in India" import machinist squares that I think I bought from Hartville Tool that are my "go to when I need a really square, square, square". I think they were $29 on sale and they are totally accurate enough to allow me to compensate with bad technique.

I also own a few el'cheapo combination squares, as well as 2 really decent ones. I love the little 4" that was my grandfather's, it's just handier than the dickens. I also own drafting triangles, Staetler (sp?) if I'm not mistaken. I also own a tape measure and know how to use the 3-4-5 method and variations there-of.

My point thru all this typing is that my method of checking square is dependent on the job at hand. For slop-**** work like carpentry, or that trash can corral I just posted, my el-cheapo squares are more than good enough and I don't risk having a crying party if I run over one of them with the truck because I left it in the driveway. For machine setup I use my import machinist squares, they're plenty good enough for me to get things plenty close enough for my experience level. What they aren't off in tolerance, I'll make up for in bad technique.

So after all that blabberin',

1.) have a decent set that you keep put away for 'special occassions'
2.) have a fairly accurate "go-to" square that you'll use all the time, but won't break your heart if you drop it on the concrete floor
3.) have a few el-cheapos that you can totally abuse for those instances where it just doesn't really matter

after all ... Huey Lewis said it best ..... it's hip to have squares (or was that BE square? )

and to answer Scott's original question, I have the 4pc set from Hartville Tool and I find myself reaching for all of them at one point or another.

[lcm1947]

Thanks to that test I just learned that both of my large framing squares are off by about 1/16' and the cheap 12' sliding square purchased from Lowes is off about the same. Too much for me to continue to use. My three Woodcrafters rosewood handled engineer squares however are dead on - thank God as well as the small I think it's a 6' sliding square also from Lowes. What I really found interesting is that both the recently purchased $2.97 orange plastic speed square I bought from Lowes is accurate as well as my 20 some odd years old Swanson speed square. They are not dead on but certainly less then 1/64". Probably couldn't hope for better then that anyway. The framers squares however are my biggest worry as I set my 3100 with them. Any body know of a good accurate framing square - if they even make such an animal.