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

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