Combination Square

Sometimes called an Adjustable Square, and even "Bevel Protractor". (Interestingly, Jeff Taylor -- cited in sources below -- calls it a "Hand Square".)

In the woodshop, the Combination Square is virtually indispensable. Its primary use is first as a measuring tool, but -- as its label suggests -- it also performs several other functions. The combination square “combines” in one tool, a rule, a square, a miter marker, a depth gauge, a height gauge, a level, a center head, and a plumb.

The combination square -- as its name indicates -- is a tool that you can use in a manner similar to the try-square. Typically, a quality combination square's removable "ruler" -- or "blade" -- is marked off in "etched gradations" of 1/8-, 1/16-, and 1/32-inch. It differs from the try-square because its “head” can slide along the blade and be set firmly at a desired place, or, when a separate ruler is needed, entirely removed.

Combined with the square is a level and a miter. Cleverly, the sliding of the head is accomplished by the combined action between a “groove” in the rule and “guide” in the square's “head”, an action which permits the rule of the combination square to be used simply as a ruler.

When using the combination square, you can "set" the head at any point on its rule, or remove it altogether. Most combination squares also have a small scratch awl stored in a hole in the base of the head. Also, typically, the head comes with a built-in spirit level, used to check horizontal and vertical members for plumb. To mark out corners for miters, the head's back edge is ground to 45-degrees. Again, while combination squares are more expensive than, say, "try squares", their range of use is greater: -- you can use them for such additional duties as a depth gauge and/or setting the height of blades and bits on routers and table saws. For the serious woodworker, this alone makes them worth the extra investment.

combination square
combination square
starrett combination square
starrett combination square

Originally a tool of engineers and architects, the adjustable square is sometimes called the "Stanley combination Try-Square and Depth-Gauge, incorporating a sliding rule". The high-end manufacturer, Starrett Tools, however, is even more famous for its version of an adjustable square. (See images on left. The upper left is an image submitted along with a request for a patent in 1914. while the lower left shows the parts of a high-end Starrett machinist's combination square. I inherited one from my machinist father-in-law. See this bio entry for Laroy S. Starrett after clicking on this link.)

The Origins of the Term, "Combination Square"

In my personal experience -- I have several of these tools, including the one pictured on the lower left -- these tools are also frequently called Adjustable Squares, but after considerable investigation, it appears that "Combination Square" is the most widely used designation, and -- if we consider Fine Woodworking as an arbiter of proper usage among woodworkers -- the correct label. (I came to the latter conclusion by way of a search for both terms in the FW database. The FW database yields no hits for Adjustable Square five hits for Combination Square. I do question my results on both terms, because, five uses of Combination Square in all the articles published in FW since its launching, 1976, doesn't seem plausible. The frequency, I think, should be greater. And unless the FW editors are pruning out uses of Adjustable Square one thinks it would have been used in 30 years of articles.)

Using one of the two Making of America databases -- and the search string, combination square, I located the United States Patent Office's Subject-Matter Index Of Patents For Inventions Issued By The United States Patent Office From 1790 To 1873, inclusive ..., which records that a D A B Bailey, St Johnsbury, Vermont, 1867, and a # 65,681; H N Burr, Mount Gilead, Ohio, 1869, # 94,867, both patented "Combination Squares". (The MOA database above is operated by the University of Michigan at Ann Arbor.)

Just to make sure that the Combination Squares patented in the 1860s are the same as the Combination Squares we know of today, I also searched for the term in the second Making of America-- the one at Cornell University -- I located more hits, including illustrations here:

"Improved Tools for Wood-Workers," Manufacturer and Builder 19, Issue 1 January 1887, page 6. The publisher of that journal is Western and Company, New York.) The Scientific American New Series, 21, Issue 14 (October 1869) page 222, confirms the Burr patent, mentioned above.

The earliest use to the term, Adjustable Square is, evidently, 1863, but -- since it's not accompanied by an image -- we can't be certain that the reference is indeed to an adjustable square as we know that tool today: Search: "adjustable square" yields two hits, one this match of 'adjustable square': Scientific American New Series,9, Issue 2, page 28. (In the second hit, I couldn't locate the evidence.)

This 1868 quote from this Google Book Search confirms that the Adjustable Square is a tool first used by machinists:

"Firmly held in this position, the adjustable square centre is simultaneously brought up against one end of the stay, and as the other is encountering the ... ."

Source: Andrew Betts Brown, Engineering Facts And Figures: An Annual Register Of Progress In Mechanical Engineering And... , 1868, page 226.

In operation, its blade can be locked at any point along its length. (The blade is held in the "stock", or "sliding head", by an assembly that combines a "hook clamp" that slides in the groove along the length of the blade, and -- anywhere along the blade --can be tightened with a bolt with a nut.)

Selected Sources: Scientific American New Series, 9, Issue 2; Andrew Betts Brown, Engineering Facts And Figures: An Annual Register Of Progress In Mechanical Engineering And... , 1868, "Improved Tools for Wood-Workers," Manufacturer and Builder 19, Issue 1 January 1887; Charles G. Wheeler, Woodworking: A Handbook for Beginners in Home and School Treating Tools and Operations New York: Putnam's Sons, 1924. page 18; International Correspondence Schools, Shop and Foundry Practice, 1901; Jeff Taylor, Tools of the Trade: The Art and Craft of Carpentry, San Francisco: Chronicle Books, 1996; Ernest Joyce, Encyclopedia of Furniture Making, NY: Sterling, 1979, page 30.

combination square

In the woodshop, virtually indispensable, first as a measuring tool, as its label suggests -- performs several other functions:

Try-Square, Marking Square, Ruler, Miter Square, depth gauge, height gauge, and plumb.

(Some Combination Squares include tiny Spirit Levels and Scribes or tiny Awls.)

Originally a tool of engineers and architects, the adjustable square is sometimes called the "Stanley combination Try-Square and Depth-Gauge, incorporating a sliding rule".

The high-end manufacturer, Starrett Tools, however, is even more famous for its version of an adjustable square. (See image blow, left; see this bio entry for Laroy S. Starrett after clicking on this link.)

starrett combination square
In my personal experience -- I have several of these tools, including the one pictured on the left -- these tools are most frequently called Adjustable Squares, but after considerable investigation, it appears thatCombinationSquares is the most widely used designation, and -- if we consider Fine Woodworking as an arbiter of proper usage among woodworkers -- the correct label. (I came to the latter conclusion by way of a search for both terms in the FW database. The FW database yields no hits for Adjustable Square, five hits for Combination Square. I do question my results on both terms, because, five uses of Combination Square in all the articles published in FWsince its launching, 1976, doesn't seem plausible. The frequency, I think, should be greater. And unless the FW editors are pruning out uses of Adjustable Square, one would think it would have been used in 30 years of articles.) Using one of the two Making of America databases -- and the search string, combination square, I located the United States Patent Office's Subject-Matter Index Of Patents For Inventions Issued By The United States Patent Office From 1790 To 1873, inclusive ..., which records that a D A B Bailey, St Johnsbury, Vermont, 1867, and a # 65,681; H N Burr, Mount Gilead, Ohio, 1869, # 94,867, both patented "Combination Squares". (The MOA database above is operated by the University of Michigan at Ann Arbor.)

Just to make sure that the Combination Squares patented in the 1860s are the same as the Combination Squares we know of today, I also searched for the term in the second Making of America -- the one at Cornell University -- I located more hits, including illustrations here:

Source: "Improved Tools for Wood-Workers," Manufacturer and Builder Volume 19, Issue 1 January 1887, page 6. The publisher of that journal is Western and Company, New York.) The Scientific American New Series, Volume 21, Issue 14 (October 1869) page 222, confirms the Burr patent, mentioned above.

The earliest use to the term, Adjustable Square is, evidently, 1863, but -- since it's not accompanied by an image -- we can't be certain that the reference is indeed to an adjustable square as we know that tool today: Search: "adjustable square" yields two hits, one this match of 'adjustable square': Scientific American New Series, Volume 9, Issue 2, page 28. (In the second hit, I cannot locate the evidence.)

This 1868 quote from this Google Book Search shows that the Adjustable Square is a tool first used by machinists:

"Firmly held in this position, the adjustable square centre is simultaneously brought up against one end of the stay, and as the other is encountering the ... ."

Source: Andrew Betts Brown, Engineering Facts And Figures: An Annual Register Of Progress In Mechanical Engineering And... , 1868, page 226.

In operation, its blade can be locked at any point along its length. (The blade is held in the "stock", or "sliding head", by an assembly that combines a "hook clamp" that slides in the groove along the length of the blade, and -- anywhere along the blade --can be tightened with a bolt with a nut.)

Sources: Scientific American New Series, Volume 9, Issue 2; Andrew Betts Brown, Engineering Facts And Figures: An Annual Register Of Progress In Mechanical Engineering And... , 1868; "Improved Tools for Wood-Workers," Manufacturer and Builder Volume 19, Issue 1 January 1887; Charles G. Wheeler, Woodworking: A Handbook for Beginners in Home and School Treating Tools and Operations. NY: Putnam's Sons, 1924. page 18;International Correspondence Schools, Shop and Foundry Practice, 1901; Jeff Taylor,Tools of the Trade: The Art and Craft of Carpentry, San Francisco: Chronicle Books, 1996; Ernest Joyce, Encyclopedia of Furniture Making, NY: Sterling, 1979, page 30.