## 6.7 Numerous Scales

Special purpose slide rules can sometimes be found with a relatively large number of scales on them. However, the slide rules with the most scales tended to be the “advanced” models used for a wide variety of calculations. Slide rules that have the largest number of distinct scales, presently limited to those with more than 20, are presented below. A single “scale” is defined as 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 4 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.

The mean number of scales on the rules of the collection is 13.2, 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 peak at about 8 scales, and another distinct distribution centered at about 22 scales. One might argue that the distinction between a “basic” slide rule and an “advanced” slide rule is showing up. (See Why Slide Rules?.)

The time progression of the distribution can be seen below.

We see that the trend line for the number of scales on the “basic” slide rules goes from about 8 in 1900, to 9 in 1940, then to 10 in 1975. (Essentially A, B, C, D, L, S, ST, and T on the earlier rules, with K, CI, CF/DF, etc., being added over time, for example.) On the other hand, a stronger upward trend of the number of scales on a typical “advanced” rule is more clearly evident throughout.

Maker Model Year Type L0 Total Scales
Pickett N4-ES 1964-1975 L 10 34
Pickett N4-ES 1959 L 10 34
Pickett N4-T 1959-1962 L 10 34
Pickett 4-ES 1958 L 10 32
Pickett N3p-T 1966 L 5 32
Pickett X-3
1975 L 10 32
Faber-Castell 2/83N 1970 L 10 30
Aristo 969 1966 L 10 29
Pickett 3-T 1953 L 10 28
Ruyi 1002 1966 L 10 28
Thornton P221
1967 L 10 27
Dring and Fage Excise Officers Rule 1845-1849 L 8 26
K&E 68-1100 1969 L 10 26
K&E 68-1130 1967 L 5 26
K&E 68-1130 1967 L 5 26
Relay-Ricoh F-686 1961 L 10 26
Dietzgen N1725 1967 L 10 25
Pickett 14 1958-1962 L 10 25
Pickett 2 1946-47 L 10 25
Relay-Ricoh 151
1974 L 10 25
Aristo 970 1954 L 10 24
Blundell Rules Limited 506 Academy Duplex 1970-1980 L 10 24
Boykin RotaRule Model 510 1965 S 50 24
Faber-Castell 62/83 1972 L 5 24
Hemmi 258 1972 L 10 24
Hemmi 258 1971 L 10 24
Hemmi 258 1969 L 10 24
Hemmi Pocket Versalog II 1971 L 5 24
Gilson Binary 1941 C 26 23
Hemmi 255 1952 L 10 23
Hemmi 257 1956 L 10 23
Hemmi 258 1967 L 10 23
Hemmi 258 1963 L 10 23
Hemmi 258 1958 L 10 23
Hemmi 258 1957 L 10 23
Hemmi 258 1953 L 10 23
Hemmi 258 1952 L 10 23
Hemmi 258 1951 L 10 23
Hemmi Pocket Versalog 1968 L 5 23
Hemmi Pocket Versalog 1965 L 5 23
Pickett N-550-T 1962 L 10 23
Aristo 968 1963 L 10 22
Dietzgen 1734
1963 L 10 22
Faber-Castell 2/82 1957 L 10 22
Pickett 600-ES 1959 L 5 22
Pickett 800-ES 1958 L 10 22
Pickett N-500-ES 1962-1964 L 10 22
Pickett N-500-ES 1962 L 10 22
Pickett N-500-T 1964-75 L 10 22
Pickett N1040-ES 1954 L 10 22
Pickett N600-ES
1964 L 5 22
Pickett N600-ES
1964 L 5 22
Pickett N600-T 1962 L 5 22
Staedtler 54408 1964 L 10 22
Sterling 694 1972 L 10 22
Sterling 694 1972 L 10 22
Aristo 958 1970 L 10 21
Dietzgen 1735 1941-1952 L 10 21
Dietzgen 1739-L 1954 L 10 21
Faber-Castell 52/82 1972 L 10 21
K&E 4081-3 1955 L 10 21
K&E 4081-5 1956 L 20 21
K&E 4083-3 1948 L 10 21
K&E 4181-1 1957 L 5 21
K&E 4181-1 1957 L 5 21
K&E 4181-3 1956 L 10 21
Relay-Ricoh 150 1972 L 10 21
UIF Shanghai 4083-3 1939-1947 L 10 21