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What are the parts of a combination square set?

What are the parts of a combination square set?


The combination square set consists of four separate parts. The three heads may sometimes be called the “stock”, and only the one being used will usually be on the rule.


Combination Square Set Square Head

The square head is primarily used for measuring right angles (90 degrees) and 45 degree angles, but can also be used for other jobs including the measurement of depths.

Combination Square Set Centre Head

The centre head is primarily used for determining the centre of round objects (such as rods), but can also be used to measure 45 degree angles (when attached to the rule) and to determine whether an angle is a right angle (when removed from the rule).

Combination Square Set Protractor Head

The protractor head is primarily used to measure exact angles with the rule.

Combination Square Set Rule (or Blade)


The rule (which is sometimes referred to as the “blade”) is the part of the combination square set onto which the square head, centre head and protractor head can be placed.


In addition, locking nuts, spirit levels and scribers are also found in combination square sets.

Combination Square Set Locking Nut

The locking nut is the part normally found on most square, centre and protractor heads. This is used to secure them to the rule. It may be known by a variety of different names, such as “screw” or “bolt”.

Combination Square Set Spirit Level

The spirit level is found on square heads and sometimes on protractor heads. It is used to determine whether a surface is flat or truly vertical (also referred to as being “plumb”).

Combination Square Set Scriber

The scriber (sometimes known by variants of this name such as “scribing tool”) is found with the square head and may be used to make marks on objects.

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