7.7 Numerous Scales

Here we list the slide rules that have the largest number of distinct scales, presently those with 24 scales or more. We designate as a single “scale” a single line or path that extends across the length or circumference of the rule without interruption. Certain scales, for example the Log-Log scales, are often broken up into a series of scales; so, one could argue that a 25 cm slide rule that breaks a Log-Log scale into four parts (LL0, LL1, LL2, and LL3, say) has a 100 cm Log-Log scale. For this list, however, we are treating these as four separate scales. On the other hand, a spiral Log-Log scale that wraps around a circular slide rule 5 times would be designated as a single scale. Measurement scales (inches, centimeters, etc., mostly found on the older rules) are not counted in the sum.

Maker Model Type Year Total Scales
Pickett N4-ES L 1959 34
Pickett 4-ES L 1958 32
Faber-Castell 2/83N L 1970 30
Pickett 3-T L 1953 28
Ruyi 1002 L 1966 28
Thornton P221 L
1967 27
K&E 68-1100 L 1969 26
K&E 68-1130 L 1967 26
Relay-Ricoh F-686 L 1961 26
Dietzgen N1725 L 1967 25
Pickett 2 L 1946-47 25
Relay-Ricoh 151 L
1974 25
Aristo 970 L 1954 24
Boykin RotaRule Model 510 S 1965 24
Faber-Castell 62/83 L 1972 24
Hemmi 258 L 1971 24
Hemmi 258 L 1972 24

The mean number of scales on the rules of the collection is 13.6, with a median number of scales equal to 11. Below is a histogram of the number of scales found on the slide rules of the collection. Note the bi-modal nature of the distribution, which shows a large collection with typically about 8 scales, and another distinct distribution centered around 22 scales.