I’ve always wondered why are there sets of squares out there. Isn’t a square a square? aren’t they all the same? Can’t you just have 1 and be done with it since if something is square…well – it’s square, right?
A recent check made me realize I probably have more squares than any other tool in my toolbox (excluding chisels and drill bits of course). How did that happen?!?
When I first started woodworking, I got myself a 12” square from the BORG. it’s an Empire Pro 12” combination square. It was always square and did it’s job well. In fact, I still have it and use it on a regular basis to this day and have nothing bad to say about it. it simply works and is very affordable It’s just that at some point, I stopped at an estate sale and found a 12” Starrett equivalent which I reviewed here (as compared to the Empire Pro square). In fact, It started to grow on me after writing the review. It’s not that the Starrett was any squarer, it’s just that it’s operation was smoother, and it’s finish more refined, easier to read, and at a higher (64th) graduation, not that I read 64th much, but when you need to it’s nice to have it, and so I repurposed the Empire square to household jobs (it has a level in it, so it does come in very handy around the house) and kept the Starrett at the toolbox.
A 12” combination square is a very handy and versatile tool. It can check for square, it can check for 45s, it can be used as a straightedge in certain situations and it can transfer square and parallel lines 12” deep into parts:
...But, since it IS this long and it does have this reach, it also means that it’s more cumbersome and less friendly to use when working with smaller parts, or for checking parts for square, not to mention good luck trying to keep this in your front pocket all day long (yes I can think of a joke or 2 and I know you can too). Enter the eBay found 6” smaller version:
Same functionality in a smaller footprint and much easier to handle as the head is smaller and can fits nicely in your palm for quick work. Also since the head is smaller it can reach into 45 corners deeper than the 12” square (good when you are setting your TS at 45 and want to verify the angle when the blade is lowered for example). Great all around square bar none with the smoothest action I’ve seen in this size.
But even that one doesn’t fit too well in a front pocket… Decided to try Rocklers 4” double square:
This one has been my all around square for the longest time. it’s small, fits in the pocket, fits in your hand for quick work, with the only down side compared to a combination square is that it doesn’t do 45 angles which is fine since the majority of my work around machines and workbench involves square and flat and for those times I do miters I can grab one of the combination squares. the 4” double square is probably the tool that gets the most use as I use it to check for square, measure small parts, and mark parts for joinery and transfer lines. Unless I need longer layout lines this one does it all.
But what I really wanted was a square that is small and can not only fit in the front pocket, but also in an apron pocket. something that just won’t take space, and be light and unnoticeable until I need to use it. For that I use a 2 1/2” precision square. Mine is a Brown&Sharpe, but other makers make a similar square (Starrett, Lufkin to name a few). I kinda like the B&S because the top of the head is beveled in where it meets the rule allowing a very clear view of the markings at the edge of the rule:
I must say of all the squares this is my favorite one. Although the all metal body and oily/sweaty fingers do call for extra care to be taken with it (wiping after use) not extreme, but something to keep in mind.
Last but not least, there is also the die maker square:
This one also has a 2 1/2” rule as well as other rules (thin, offset, 45/30 angles), but it’s unique feature is that the rule can be set to anywhere between 0-10 degrees off square which is really meant to check the offset of dies, but in woodworking can be used to layout dovetails or similar geometry:
And so looking back, from just needing a square, this collection has grown quite a bit:
You can kinda see which one gets the most use right there, but the funny thing about it is that they all see use on a regular basis.
Checking for Square
So what good is it having a square if it isn’t a square? or wait a minute… how would you even know if your square is a square? use another square? what is that square isn’t square either? use a 3rd square? oh boy…
There are several ways to check a square for squareness. Some requires more measuring tools then others, some providing quicker results then others, some providing more accurate results then others. For sake of woodworking, the following are 2 ways to check your square for squareness. One requiring an additional device that I believe is available for purchase or can be made and provides with a faster and more accurate result, while the other doesn’t really take much to achieve and can be done in any shop at any time and like I said for the purpose of woodworking is just as good as any other method.
The Round Square
What you say? round square? how is that even possible? and how would you check a square with a round object?
The answer is explained in the method of making the measuring device, the Cylindrical-square. A cylindrical square is a cylinder that is made on the lathe to very high tolerances. The idea is that if the cylinder is turned to be of consistent diameter across it’s body than that means that the sides are totally flat and parallel to the axis of it’s rotation (on the lathe). If then the base is faced totally perpendicular to the axis of rotation then that results in the base and the side of the cylinder being square. In fact the base doesn’t even need to be highly machined as long as the circumference of the base is faced properly and there are more details about it, but that probably won’t make this any clearer so I’ll stop here.
Using a flat reference surface (granite for example) and a cylindrical square is a fast and accurate way to check a square for squareness if it’s rule makes full contact throughout it’s length with the cylinder when placed next to it:
The Straight Edge Method
If you don’t have a flat reference surface and don’t have a cylindrical square (like most of us don’t) then an alternative to checking a square for squareness and in my opinion what should be named ‘the official woodworker way to check a square’ is to use a surface with a known straight edge (jointed on the jointer, or another known surface/part that has a straight edge – yes even using a straight edge).
Butt you square against the straight edge of the part on one side of the square, and mark a line down it’s rule:
I like using a mechanical pencil as the lines produced are always fine, and always consistent in width and sharpness (I use softer graphite so it does not gouge the wood) and it should look like this:
Pretty isn’t it?
Now flip your square and butt it against the same straight edge now with the square facing the other way, align the rule with the previously made line and mark another line (yes I can use both hands):
If your square is out-of-square you will probably see something like this:
But if your square is indeed square, the 2 lines should merge into one, and what you will hopefully see (what you WANT to see) which verifies your square is indeed what its named after is this:
Just make sure the rule in your square (if you have an adjustable square) is properly positioned and locked in the head and that there are no debris or dents on the head of the square that otherwise WILL introduce and error and throw your readings way off.
Now you can feel good knowing your square is up for the challenge you present it with everyday you use it. Hope this was useful and if not at least entertaining and if not then there isn’t much I can say since I will not be reimbursing anyone for lost time ;)
Thanks for reading,
-- ㊍ When in doubt - There is no doubt - Go the safer route.