Carpenter's Slide Rule by S. A. Jones

One of the first types of slide rules sold and made in the United States was the carpenter's rule, used for calculations relating to timber, which was one of the country's major early exports. This rule is marked on the lower arm: S. A. JONES & CO. (/) HARTFORD–CON. (/) WARRANTED BOX WOOD. Solomon A. Jones made carpentry tools in Hartford, Conn., from 1838 to 1841. Compare to 1987.0771.01, a British carpenter's rule of the same period. The collections include an image of someone holding the rule (see 2003.0215.02).

This boxwood carpenter’s rule has a brass joint, metal caps at the ends of the arms, and a brass slide. The front of the slide has two identical logarithmic scales labeled B and C. Above is an identical logarithmic scale on the arm; this scale is labeled A. All three of these scales have a double cycle of logarithms, like the A and B scales on a Mannheim rule. Below the C scale on the arm is a scale labeled D and also GIRT LINE, which is divided logarithmically and runs from 4 to 40 (in other words, this is not the D or principal scale of Mannheim slide rules). The girt line can be used with other scales to estimate the volume of timber available from a log.

Underneath the slide is imprinted the number 33. The back of the slide is also stamped with the number 33 and is somewhat crudely marked with a twelve-inch ruler, divided to eighths of an inch. The lower arm contains scales for making scale drawings that are 1/4, 1/2, 3/4, and 1 inch to the foot. The units on the 1/4-inch chain scale appear to be numbered erroneously after 18 (e.g., the next numbered division after 18 is 10 rather than 20). Along the edge is another twelve-inch scale, divided to eighths of an inch.

The other side of the rule has a scale of 24 inches along one edge, divided to sixteenths of an inch. One arm has a scale labeled by twos from 34 to zero and is marked M. A number for 31 is between 32 and 30, and the number for 6 is omitted.

The other arm has a scale marked E and labeled by twos from 24 to zero. The number 24 appears twice, and 6 is omitted. The M and E scales were used in cutting polygonal sections of wood. The outside edge has two scales, each dividing one foot into 100 parts.

References: Kenneth D. Roberts, Introduction to Rule Collecting (Hartford, Conn.: The Bond Press, Inc., 1982); "Solomon A. Jones & Co.," The Davistown Museum, http://www.davistownmuseum.org/bioSAJones.html.

Currently not on view