Smithsonian museums continue to be closed to support the effort to contain the spread of COVID-19. Read a message from our director, and check our website and social media for updates.

Safe-T 45749 Compass

Safe-T 45749 Compass

<< >>
Usage conditions apply
This translucent light orange plastic instrument is wedge-shaped, with a rotating white plastic disc set inside the wide end of the wedge. One long edge of the wedge has a scale of four inches, divided to 16ths of an inch. The other edge has a scale of ten centimeters, divided to millimeters. These edges each have a row of 33 small circular holes. The holes are marked for the radius of various circles, from 1" to 5". To draw a large circle, a pencil is placed in the desired hole and the instrument is rotated while the user holds the disc.
Two rows of four small holes are on the disc; one row is straight and one is bowed. The disc also has a small hole at its center. To draw a small circle of up to 1-5/8" diameter, a pencil is placed in the desired hole and used to rotate the disc, while the wedge is held in place. Five larger circles are around the edge of the disc. The wedge is marked: SAFE-T (/) COMPASS® (/) LaGrange, IL 60535-0692 (/) #45761 Pat. #4,353,166. It is also marked: π = 3.1416 (/) A = πr2 (/) C = πd.
Instructions are on white cardboard received with the instrument. According to a company catalog (1998.0033.04), model number 45759 sold for $1.19 around 1998. The design of the disc is covered by a patent received by John S. Kettlestrings of Wheaton, Ill., in 1982.
Safe-T Products, Inc., of La Grange, Ill., was established in 1992 and specialized in drawing instruments that were safe for children. In 2006, the company became a subsidiary of A. Daigger & Company and its name changed to Classroom Products Warehouse. Kettlestrings (b. about 1933) is an inventor, designer, and entrepreneur who was associated with Tool-Less Hanger Corporation of Everson, Wash., in 2011.
References: SAFE-T Products, Inc., Innovative Safe Drawing and Measuring Instruments, about 1998; John S. Kettlestrings, "Toy-Like Instrument for Drawing Circles" (U.S. Patent 4,353,166 issued October 12, 1982); Company Overview of Safe-T Classroom Products, Inc.," Bloomberg BusinessWeek,; "About Us," Classroom Products Warehouse,
Currently not on view
Object Name
compass, drawing
date made
Safe-T Products, Inc.
place made
Physical Description
paper (overall material)
plastic (overall material)
overall:.4 cm x 5.2 cm x 16.7 cm; 5/32 in x 2 1/16 in x 6 9/16 in
ID Number
catalog number
accession number
Credit Line
Collected at the American Mathematical Society annual meeting, 8 January 1998
Drawing Instruments
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Dividers and Compasses
Data Source
National Museum of American History
Nominate this object for photography.   

Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.

If you would like to know how you can use content on this page, see the Smithsonian's Terms of Use. If you need to request an image for publication or other use, please visit Rights and Reproductions.

Note: Comment submission on our collection pages is temporarily unavailable. Please check back soon!

If you have a question or require a personal response, please visit our FAQ or contact page.