Dividers With Exchangeable Points

For several hundred years some dividers have been constructed so that the lower legs or points can be switched. One tool can serve as dividers as well as inside or outside calipers and other functions. The earliest pair of dividers with this option that I’ve come across on line belonged to Michelangelo and are in the Museo Galileo in Florence. These would likely date from the early 1500’s. Notice that this tool comes with several leg options including pen holder and marking wheel as well as caliper points. 

                                                   

Michelangelo's Compass, Museo Galileo

 Michelangelo’s dividers show what is likely the earliest form of point attachment to the body of the tool. In this method the point has a “tenon” on the end that fits into a socket in the upper leg and is held in place by a locking nut. Below is an example from my collection likely dating from the 18^th century. It includes outside caliper, inside caliper (only one), short points and a holder for a crayon or other marker. The tool is unmarked.

                                                            

 A second, later method of attachment is similar to the above, but in this case the lower, solid legs slip entirely into the hollow, upper leg section and are again fixed in place by lock nuts. The J. Stevens Arms & Tool example (No. 64) below is an example of this technique.

 

                                                  

These dividers are marked with a patent date of 14 Feb. 1888, but that Stevens patent does not apply to this tool. The correct Stevens patent is 22 Jul. 1890.

Two other examples of this arrangement are shown next.

                                                   

Lt: Unmarked, but similarities to Stoddard.    Rt. Starrett No. 90 (not marked)

                                   

 A third and possibly the most recent method of leg attachment is to set the lower legs  into grooves that run along the upper legs. The lower leg is held in the grove by an encircling band with a wing nut. 

                                            

J. Stevens Arms & Tools, No. 61

Sometimes this involves both legs or just one. Instead of a metal lower a leg, a pencil can be inserted converting dividers into compasses. Here are five examples of this method.

                                            

Top lt: Stanly #58, Top rt. Unmarked

                               Center: Cook's 18 Feb. 1873 pat. Bottom lt. Peck, Stowe & Wilcox                                                                                   Bottom rt. Miller's 11 Nov. 1873 pat.    

 

Not surprisingly, it is easy to lose the original lower leg pieces so complete sets are uncommon. Another issue that arises is dividers turning up with lower legs that fit into or along side the upper legs, but may not be original to the tool. This situation can be hard to identify.