Collection of pages from K&E catalogs for the 4090-3 & 4091-3 Family of Slide Rules


The 4090-3 and 4091-3 family of slide rules are duplex type of slide rules. The 4090-3 and 4091-3 were constructed on a mahogany frame with celluloid laminated to the surface. The markings are engine divided. Of the catalogs available the first release was shown in the 1933 catalog.

This is the first series of slide rules called "Log Log Duplex Trig" (4090-3) and "Log Log Duplex Decitrig" (4091-3). These rules are identical except for the scale graduations of the trig scales. The 4090-3 is divided in degrees and minutes where as the 4091-3 is divided in degrees and decimal degrees on its trig scales. This is the first occurrence of the Trig and Decitrig versions. This split is used in late families of slide rules such as the 4081 and 4071 families.

After reading Bill Robinson's paper "Mendell Penco Weinbach and the K&E Log Log Vector Slide Rules" it is clear that the Decitrig version was inspired by Weinbach's 4093-3 design. The decimal divided trig scales are necessary for vector calculations and the 4093-3 is the first known implemtation of these scales.

These two slide rules are a short lived evolvement of the 4092-3 by adding the double sin scales and rearranging all of the scales. The 4090-3 and 4091-3 evolved into the first release of the 4080-3 and 4081-3 in 1937 which became the main stay of the K&E line into the 1960s. The 4080 and 4081 family would see much more evolvement but its roots are in the 4090 and 4091 family.

The 4090-3 does appear in the 1939 price list for some strange reason. It was probably an error as it was not in the 1939 slide rule catalog.

There are 2 scale sets shown in the available catalogs. The scale set for the 4090-3 and 4091-3 shown in the 1933 catalog is as follows:

The scale set for the 4090-3 and 4091-3 shown in the 1934 catalog is as follows:


The 4090-3 and 4091-3 were probably released some time between 1932 and 1933. The 4090-3 and 4091-3 last appeared in the 1936 catalog. The 1937 price list announces the release of the 4080-3 and 4081-3 and that they replace the 4090-3 and 4091-3. The following is a brief history of the 4090-3 and 4091-3 as is told in the K&E catalogs that are available at this time. Exact timing is not possible because of the time between catalogs.

Links to catalog pages for the 4091-3 family of slide rules:

Link to scans of 4090-3/4091-3s