What is a Combination Square Used For?

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In woodworking, it is essential that the piece you are building is square, no matter the piece.  Think of your house; if the framing wasn’t square, if the door frames weren’t square, if the room’s corners weren’t square, what a mess your house would be, if it would even stand.

How do we ensure an angle is square?  Well, the obvious answer is we use a square.  Depending on the project you are working on, you might use one of several squares.  How many types of squares are there?  Here are a few:

  • Try Square. It’s a tool used to measure, mark and confirm 90 degree angles on pieces of wood.  Used to “try” how square your workpiece is (thus the name), you will use a try-square to make sure the edge and face are straight, flat, and square to each other.
  • Miter Square. A hand tool used to mark and check angles other than 90 degrees.  Most are made to mark and check 45 degree and its supplementary 135 degree angles.
  • Speed Square. Also called a rafter square and a triangle square (because of its triangular shape), these squares are used for marking out.  Remember that out-of-square framed house we mentioned?  This speed square would be used to measure rafter cuts, for instance.  It’s a multipurpose square, though, and a good layout tool to have in your workshop.  The “speed” in speed square comes from its simple triangular shape.
  • Combination Square. This layout tool is as versatile as they come.  It is a steel rule (a removable blade) that slides through a protractor head that is easily adjusted and set along the rule by a lock bolt.  A protractor is a device for measuring angles that you may remember from high school math classes (compasses and protractors were essential in geometry class).  

A combo square can be used to measure inside and outside angles, as well as a marking device, a miter square, a try square, a plumb, and the rule, can be used as a straight edge. It can measure length and depth, check square and 45 degree angles, and its simple bubble level can indicate plumb and level.

How Do You Use A Combination Square Protractor?

Starrett C435-12-4R Combination Set, Cast Iron Heads, Satin Chrome Blade, 12", 4R Grad,

The rule, a removable blade, is calibrated as a standard wooden ruler.  A combo square is usually broken down into whole inches, eighths, sixteenths, and thirty-seconds.  Switching the rule around will present each of the measuring options.  It has a center slot that enables the protractor head to slide along the rule to the desired length, and a lock bolt helps set that protractor head accordingly.

It can easily and quickly measure 90 degree and 45 degree angles, and the rule allows for easily marking lines on your workpiece surface with your always handy carpenter’s pencil.  The protractor head is wide enough on each side of the rule so it can tightly abut the piece being measured and maintain the integrity of the angle and length measurements being taken.

If you have seen a combination square, you’ll have noticed it’s a pretty easy hand tool to understand and figure out its use fairly quickly.  If you haven’t, we found a video that will show you the basic ins and outs of one.

It’s an old video but is an apt one to suggest that both demonstrates and explains all of this, and you’ll find it here.

The combo square is the most versatile measuring device your woodworking shop can have, and every shop should have one.

How Much Does a Combination Square cost?

Like any tools, power and hand, cost depends on brand and size.  Combination squares come in 6” rule length, 12” rule length, and up to 24” rule length.  While 6” combo squares might fit easily in your work apron, you’ll want to have a 12” size for larger workpiece measurements.  The difference in size isn’t significant, but having the larger of the two makes most projects easier.  

Among the top brands of combo squares are:

Empire: A 12” combination square from Empire can run as low as around $11 and less for a 6” size. 

Empire Level E250M 12-Inch Heavy Duty Professional Combination Square With Etched Stainless Steel Blade, Metric Graduations and True Blue Vial

Starret: A 6” combination square from Starret, considered the gold standard in combo squares, will start at just under $50; a 12” model will run you close to $150.  We also found a 4-piece 12” set (rule and three heads) for $277 and even a cast iron 12” model with three heads for $280.

Starrett Combination Square, C11H-12-4R - Pre Cutting and Drilling Measuring Tool for Right Angles and Center with Heavy Duty Square Head, 12" for Woodworking, Carpentry, Machinists

While the price of Starret models might seem high, this is a tool that will outlive you and your woodworking shop.  You’ll be able to pass it on to your helpful daughter or son, who will carry on your woodworking hobbies, along with all of your other tools.

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