Safe-T 45749 Compass

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.
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
place made
ID Number
catalog number
accession number
Science & Mathematics
Drawing Instruments
Dividers and Compasses
See more items in
Medicine and Science: Mathematics
Dividers and Compasses
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Collected at the American Mathematical Society annual meeting, 8 January 1998
Additional Media

Visitor Comments

Add a comment about this object

**Please read before submitting the form**

Have a comment or question about this object to share with the community? Please use the form below. Selected comments will appear on this page and may receive a museum response (but we can't promise). Please note that we generally cannot answer questions about the history, rarity, or value of your personal artifacts.

Have a question about anything else, or would you prefer a personal response? Please visit our FAQ or contact page.

Personal information will not be shared or result in unsolicited e-mail. See our privacy policy.

Enter the characters shown in the image.