# How Square is your Square?



## paduke (Mar 28, 2010)

A geat topic for all woodworkers to consider. 

For 84.00 USD a 4 piece set of squares can be purchased that are accurate to 0.0006. Which says it ain't truly square. As we strive for accuracy, a thread regarding how "slop" is tolerated and what techiques are employed for accuracy should be fun and informative for all. :no:

I will add my own techniques if the thread is of interest to others


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## Marco (Feb 21, 2009)

I have a framing square that I check to make sure is square Check & Repair A Framing Square - NewWoodworker.com LLC and use it when the project is big enough. I also have 4 plastic clamp it squares from Rockler Clamp-It® Assembly Square with 5'' Bar Clamp (Sold Separately) - Rockler Woodworking Tools that I know are square for smaller projects. When building tables/boxes/drawers measuring from corner to corner then corner to corner will put me close to square and if the box is big enough the clamp it squares help. When squaring up the table saw sled I cut a 12 to 20 inch wide piece of sheet good with the factory edge to the fence 16 or so inches long then take that cut piece, flip it and press it against the sheet good that it was cut from. If it is flush then the Table saw sled is square.One Cut Method For Squaring Miter Gauges / Crosscut Sleds / Sliding Tables 

I"m not saying my projects are perfectly square but since NASA isn't the clent it's square  

I hope others will post their squaring techniques as I would like to incorporate them.


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## Cherryville Chuck (Sep 28, 2010)

Accurate to .0006 is pretty good for a machinist, overkill for woodworking. With that said, I have read numerous times how to make a common framing square accurate if it is not, which tells me that they often are not. A cheap one that I bought recently is proof. If you put it on a factory edge of something like mdf, it will not follow the same line when flipped over.


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## argoknot (Dec 7, 2009)

I seldome use a big square. My tools of choice are a protractor and a 45/90 triangle. I find that using them is as accurate as you can get for woodworking.


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## OPG3 (Jan 9, 2011)

I build some pretty accurate items from time-to-time in my prototype shop. Here is how I think about squareness: it is a great "bull's eye", but it is silly to lose sleep over it when one is working with _*lumber*_- the part can be perfect one day and slightly off when the humidity changes. On dovetails and finger joints - it is great to be super-precise and certainly common-sense dictates the need for squareness of construction. In the case of accurate to 0.0006, heck nobody out there can show me someone who can look at a pencil line for accuracy of that tightness. Get real! If you cut something "square" and flip it over and it still aligns visually - you're either good enough or in need of an optometrist. There are better things to worry about than 0.0006"... *OPG3*


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## Dal300 (Jul 14, 2011)

0.0006?

Aircraft engine rod and main bearing don't get that precise.

I dealt with Truck, Bus and Auto engines for about 40 years.... 0.005 was the outside limit on a lot of them and 0.0015 was the smaller limit.

Try hanging an exterior door with the 0.0006 tolerance.... it might work great when you do it, but in a couple of hours it'll stick tighter than you could ever believe.

I like to have 'em tight, but too tight isn't good for Mr. Happy!:wacko:


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## harrysin (Jan 15, 2007)

I've said it so often on this very forum, precision metalworking accuracy for wood is ridiculous, as has been stated, the weather changes and with it the wood.


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## xplorx4 (Dec 1, 2008)

I got a set free from a guy getting rid of tools, wood and all. I could care less about the .0006, or whatever but the small size is nice for getting into tight spots and for checking fences on joiner, router, TS, DP and band saw I doubt mine are anywhere near .0006, been dropped!!


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## papawd (Jan 5, 2011)

I have real nice sqaure from Woodpeckers tools and often find myself using the cheap ole Stanley depending on what I am building


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## bobj3 (Jan 17, 2006)

HI Harry


I will 2nd. that 

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harrysin said:


> I've said it so often on this very forum, precision metalworking accuracy for wood is ridiculous, as has been stated, the weather changes and with it the wood.


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## paduke (Mar 28, 2010)

As Harry says such precision is for metal not wood. 1/64th of an inch is 0.015625
Yet somebody is buying some very pricey precision tools judging by the tool catalouges. I can barely see a 64th with my eyes. I do better seeing it with my finger tips. 

So how close is close in your shop?


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## AxlMyk (Jun 13, 2006)

I like to be accurate, as I spent 20 years repairing precision tools.
But I use the cheap plastic drafting triangles, and a Wixey angle finder for setup.
Works for me.


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## iflyfish2 (Nov 13, 2011)

*My 2 Bits*

I use 4 different types in addition to a .05mm pencil lead:

1) Combo square--some machine setup, checking dado depth, squaring small pieces

2) Engineering square--machine setup, jig setup

3) Handmade wooden square--larger stock and layout

4) Finger tip--if it feels close, I can live with that.

I worked in a cabinet shop that set door gaps for inset doors to around 3/32". Their clientele was in the northern suburbs of Chicago--Wilmette, Evanston, places like that. If they could do that, then that's what I shoot fore. I'm working with wood, not metal.


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## gav (Oct 12, 2009)

I have an old Maples square from my Grandfather, and I used to trust, but not any more. It's seen better days.
I wanted to buy a new one but when I went to the hardware store, I compared all the squares and none were the exact same as the others. Not just small differences either. How I am I supposed to know which one was square ? I then when to a department store and compared the plastic triangles against each other, and they almost all were the same.
Now I only trust a plastic triangle, or a copy I've made of it for square.


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## Phil P (Jul 25, 2010)

gav said:


> How I am I supposed to know which one was square ? I then when to a department store and compared the plastic triangles against each other, and they almost all were the same.
> Now I only trust a plastic triangle, or a copy I've made of it for square.


Hi Gav

There's a very simple, very old test, if you didn't know it. Offer up the square to a straight edge and mark a line using the inside of the blade. Flip the square over and line up the inner edge of the blade with the line you've just drawn. If the edge of the blade and the pencil line don't line up then the square isn't (square). BTW did you know that woodworkers squares are generally only made with the inside edges square (or approximately)? That's why I now use a couple of low cost engineer's all steel squares. 

Regards

Phil


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## bobj3 (Jan 17, 2006)

Amazon.com: Incra GSQR5 Guaranteed Square 5-Inch Precision Square: Home Improvement

http://www.amazon.com/Incra-GSQR5-G...dp_top_cm_cr_acr_txt?ie=UTF8&showViewpoints=1

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## wbh1963 (Oct 11, 2011)

Considering that I picked up my first RAS a few days ago, the timing of this topic is quite coincidental. 6 out of 15 steps in setting it up involve using a square.

The first step laid out in the manual for the RAS is to "make sure the framing square is true". The book specified the 'draw a line & flip the square' technique for checking it.

My collection of squares is humble and basic. I use the 6 inch plastic square the most, but also use a generic steel framing square and a 12" plastic one.

When the pieces will fit together and the item being made functions as needed I generally consider it to be 'square enough'. I consider 'appearance' to be a form of function and 'joint integrity' often relies on squareness.

The 'wow' reaction to the .0006 tolerance of the set mentioned didn't survive the sticker shock of the price tag, especially when working with wood. I don't mean to say that the product isn't worth the price to some people for their applications, simply that it has no appeal to me. 

The other thing that came to mind when wondering 'how square is my square' is the realization that the whole concept of squareness is angular. Absent a line length to feed into the equation, the .0006 tolerance end to end can not be translated to degrees, which is what squareness is all about!


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## RJM (Apr 11, 2010)

I use a framing square that I beleive is accurate but I'll have to check. For setup, I have a Wixley angle gage and a pair of 1-2-3 machinist blocks (accurate to .0002 over the 3 inch span) that I use to make sure all other measuring devices are square. I also have various size plastic drafing triangles that are good for measuring 30°, 45°, 60° and 90° angles, although I haven't ever checked them (at least not recently).

I'm sure the OP knows that accuracy to 1/2 a mil is not needed for woodworking (I've read many of his posts) but it's nice to be able to know that your setup tools are accurate (Read This).

Also, good measuring tools (i.e. scales, protractors) have to be made with a high degree of accuracy to prevent accumulated error. BTW, good box levels are accurate to .0005 inches/inch and these are used for ... framing!


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## annaatkins (Nov 30, 2011)

harrysin said:


> I've said it so often on this very forum, precision metalworking accuracy for wood is ridiculous, as has been stated, the weather changes and with it the wood.


I agree, precision looses it's sense when it comes to wood. Cause no matter how precise you are wood's still gonna change!


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## RJM (Apr 11, 2010)

annaatkins said:


> I agree, precision looses it's sense when it comes to wood. Cause no matter how precise you are wood's still gonna change!


 
Try making a box with miter joints on all 4 edges of all 6 sides and get back to me. Make it easier by using MDF.


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