Squares

Squares are used to alight objects, mark straight lines, and check for proper fit or assembly of machines.

Types of Squares

  • Combination Square - The combination square consists of a grooved ruler that accepts multiple different heads for different functionality. The most commonly used head has a 90 and 45 degree angle, along with a scribe and level used to check level/plumb of the part. There are also variable angle and “V” attachments used to measure arbitrary angles and the center of round dowels respectively.

  • Try Square - Named because it is often used to “try” a surface for squareness, the try square is most commonly used to test and mark wood pieces. It is commonly made of a wooden stock with riveted metal blade. The try square is very similar is use to the machinist’s square.

  • Sliding T-Bevel Square - This square is often referred to as a “false square” as it is an adjustable blade square. The blade can be set to the desired angle using a protractor, or more commonly the T-bevel is used to transfer an angle by setting it on the original piece and then marking another piece.
  • Machinist’s Square - The machinist’s square is the metalworking version of the try square. They are manufactured to very high precision, generally in A and B grades with deviations of much less than a thousandth of an inch per inch of run. These squares are made of metal that is pinned and should be checked for accuracy periodically. The most common use of the machinists square is workpiece marking and tool alignment.

  • Speed Square - Invented in 1925, this is a very versatile square and one that is often reached for when making 90 or 45 degree marks. The square includes carpentry features to easily measure roof pitch and other common tasks. The speed square is available in 7” and 12” models made of metal or plastic. The Swanson tool co. (the original designers and manufacturers) offer a small book to accompany the squares describing their various uses.

Use

Squares are adjusted to the desired angle (if applicable) and aligned with the workpiece. They are then used as a guide, marking tool, or visual inspection tool. The video above demonstrates many of the common uses of squares in the shop. Squares that are dropped or experience extreme temperatures should always be checked before use as they could have been damaged.

Safety Precautions

Some squares may have sharp edges, wearing gloves is recommended with such squares. If the square is going to be used as a cutting guide, it must be firmly clamped, otherwise it could become a projectile.