Description and Components
– Combination set with a rule, standard head, protractor head, and centre finder head
– Rule made of steel with gradations in metric, imperial, or both
– Different markings on both faces of the rule
– Length of the rule ranges from 150mm to 600mm or 4 inches to 24 inches
– Heads attached to the rule by sliding it into a slot and tightening with a lock bolt or nut
Rule Details
– Made of steel with metric, imperial, or both markings
– Both faces of the rule have markings, providing four different sets
– Lengths between 150mm and 600mm or 4 inches and 24 inches
Head Details
– Attached to the rule by sliding it into a slot
– Heads are made from forged steel, cast iron, die-cast aluminium, die-cast zinc, or plastic
– Aluminium and zinc heads are cheaper but less durable
– Cast iron and steel heads are heavier
– Heads usually painted except for the machined reference faces
Uses
– Used as a regular standalone rule or straightedge
– Standard head can be used as a square, mitre square, spirit level, depth gauge, and marking gauge
– Protractor head used for measuring and checking angles, marking angles, transferring angles, and using the spirit level
– Centre finder head used for marking lines through the center of circular or square objects, marking perpendicular lines, and bisecting square corners
– Combination square minimizes measurement errors and inaccuracies
History
– Invented by Laroy S. Starrett in the late 1870s
– Patented in 1879
– Originally designed for machinists
– Became commonly used in other trades, such as woodworking
– Laroy S. Starrett founded the L. S. Starrett Company in 1880 Source: https://en.wikipedia.org/wiki/Combination_square
A combination square is a multi-purpose measuring and marking tool used in metalworking, woodworking, and stonemasonry. It is composed of a rule and one or more interchangeable heads that can be attached to the rule. Other names for the tool include adjustable square, combo square, and sliding square.
 A Starrett combination square with a standard head | |
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| Inventor | Laroy S. Starrett (1877) |
The most common head is the standard head, which is used as a square for marking and testing 90° and 45° angles. The other common types of head are the protractor head, and the centre finder head.
