Slide Rules

The first device which could properly be called a slide rule was invented around 1622 by Anglican minister William Oughtred, based on John Napier's discovery of logarithms as described in his 1614 publication Mirifici Logarithmorum Canonis Descripto. Oughtred's slide rule consisted of two C/D-style sliding scales which he used to perform multiplication and division. This basic operation would serve as the backbone of nearly every slide rule manufactured for the next 350 years.

For the next two centuries, the capabilities of the slide rule evolved slowly, gaining square and cube scales in the early 1700s and log log scales in the early 1800s. In 1851, French artillery officer Amedee Mannheim developed the first "modern" slide rule, with multiplication/division scales marked C and D, and square/square root scales marked A and B. Mannheim's design also popularized the inclusion of a cursor, first suggested by Isaac Newton in 1675. The final major design change was the invention of the duplex slide rule by William Cox. The duplex slide rule has scales on both sides and a two-sided cursor used to align scales from opposite sides of the slide rule. The duplex slide rule was first sold by Keuffel & Esser in the late 1800s, but soon became the industry standard for professional slide rules from all manufacturers.

Despite the wide range of calculations which can be performed on a slide rule, inherent limitations typically confine result accuracy to betweeen two and four significant digits. Long calculations can also be tedious, unintuitive and time-consuming. These limitations became an extreme vulnerability in 1972, when Hewlett-Packard introduced the first handheld electronic scientific calculator, the HP-35. Early scientific calculators were much easier to use, and typically produced nearly instantaneous results with at least ten digits of accuracy. Although slide rule adoption had only accelerated up to this point, the electronic calculator would become a totally disruptive technology, wiping out the entire slide rule industry before the end of the 1970s.

Acu-Rule Acu-Math 511
 Acu-Rule Acu-Math 511

Acu-Rule began in 1938 as the Festus Manufacturing Company, a Depression-era producer of affordable student-grade slide rules. Festus initially manufactured wood-body slide rules with paper scales, and also provided extra production capacity for other slide rule manufacturers such as Dietzgen and Post. By 1939, Festus had been renamed as the Acu-Rule Manufacturing Company, and soon began selling slide rules under the Acu-Math brand name. The Acu-Math 511 is a 10" Mannheim-style simplex slide rule with nine scales and a non-reversible slide. The Acu-Math 511 is a later example of Acu-Rule's product line, featuring a magnesium body laminated with engraved vinyl scales.

Available Scales: S K A [B CI C] D L T

[View Detail]

Better Ideas New American Metricaddy
 Better Ideas New American Metricaddy

Introduced in 1976 at the height of the United States' metrication hysteria, the Better Ideas New American Metricaddy is a later iteration of the Creative Workshop Universal Circle Metric Converter. The Universal Circle Metric Converter was designed by Ole Jorgensen in 1970, and introduced alongside his better-known Universal Circle Slide Rule. Both of these devices share a similar pencil cup form factor and slide function. The New American Metricaddy adds a number of conversion factors not present on the original Creative Workshop device, and is capable of converting among 40 different units of measure. The New American Metricaddy has a three-part stator printed with conversion units, and two rotating slides printed with logarithmic scales.

[View Detail]

Creative Workshop Universal Circle Slide Rule
 Creative Workshop Universal Circle Slide Rule

Designed in 1970 by Ole Jorgensen of Creative Workshop, the Universal Circle Slide Rule is an unusual logarithmic slide rule with a pencil cup form factor. The Universal Circle Slide Rule has a base which functions as a stator, with five rotating slides stacked atop one another. This slide rule abandons traditional Mannheim-style labeling, with eight scales labeled either X, X2 or X3. The first slide has a single X3 scale which functions like a traditional K scale. The second and third slides each have dual X scales which are equivalent to C and D scales. The fourth slide has a fifth X scale and a X2 scale which is equivalent to an A or B scale. The fifth slide has a second X2 scale.

Later variations of this slide rule were produced in Hong Kong by Better Ideas.

Available Scales: [X3] [X X] [X X] [X X2] [X2]

[View Detail]

Dietzgen 1748P
 Dietzgen 1748P

The Dietzgen 1748P is a compact 8" 'Maniphase' slide rule, derived from a traditional Mannheim simplex slide rule with the addition of K, C and CI scales. The 1748P also has a reversible slide with S, L and T scales on its reverse, inch and metric rulers along the top and bottom edges of the stator, and a printed conversion table affixed to the stator's reverse. Like other Dietzgen slide rules of this style, the 1748P has a mahogany body laminated with engraved celluloid faces, and features Dietzgen's proprietary 'frameless' glass cursor which can be removed from the stator without the use of tools.

Available Scales: K A [B CI C] [S L T] D

[View Detail]

Keuffel & Esser 4053-3
 Keuffel & Esser 4053-3

Manufactured continuously from 1910 to the early 1970s, the Keuffel & Esser 4053-3 is the definitive example of a 10" polyphase slide rule - a Mannheim-style simplex slide rule with additional C and CI scales for handling cubes and cube roots. The 4053-3 also has a reversible slide with S, L and T scales on its reverse, inch and metric rulers along the top and bottom edges of the stator, and a printed conversion table on the stator's reverse. The 4053-3 pictured here is a later example, manufactured in the mid-1950s, with a celluloid-laminated mahogany body affixed to a plastic base.

Available Scales: A [B CI C] [S L T] D K

[View Detail]

Keuffel & Esser 4081-3
 Keuffel & Esser 4081-3

Introduced in 1937, the Keuffel & Esser 4081-3 is a log log duplex 'Decitrig' slide rule with 10" scales. Instead of being divided into degrees and minutes, the trigonometric scales of the 4081-3 are divided into degrees with decimal graduations. The 4081-3 was manufactured for over 35 years, with numerous scale revisions over its production lifespan. The example pictured here has 23 scales, and was manufactured after 1954. Like most K&E slide rules, the 4081-3 has a mahogany body laminated with engraved celluloid.

Available Scales: LL02 LL03 DF [CF CIF CI C] D LL3 LL2 ||| LL01 L K A [B T Cot SRT S Cos] D DI LL1

[View Detail]

Keuffel & Esser N4083-3
 Keuffel & Esser N4083-3

The Keuffel & Esser N4083-3 is a powerful 24-scale log log duplex vector slide rule, based on their popular 4080-3 and 4081-3 log log duplex models. The N4083-3 omits the K scale of the 4081-3 in favor of three vector scales, used to calculate sinh and tanh.

Available Scales: LL02 LL03 DF [CF CIF CI C] D LL3 LL2 ||| L LL01 LL1 A [B T Cot ST S Cos] D Th Sh2 Sh1

[View Detail]

Nav-Comp E6B
 Nav-Comp E6B

The Nav-Comp E6B is one of many iterations of the original E-6B / AN-C-74 "whiz wheel" flight computer, developed by Naval Reserve pilot Lt. Philip Dalton in the 1930s. First adopted by the U.S. Army in 1940, the E-6B is capable of estimating a wide range of flight parameters, including ground speed, fuel burn, wind correction and ETA. The E-6B is one of the few slide rules still in wide use, with metal, plastic and cardboard versions available from a wide range of manufacturers. The Nav-Comp E6B pictured here is constructed out of aluminum and nylon, and has lithographically applied scales.

In popular culture, the E-6B is probably best known for its anachronistic appearance in multiple episodes of the original Star Trek television series.

[View Detail]

Pickett N500-ES
 Pickett N500-ES

The Pickett N500-ES is a 10" hi-log duplex slide rule, with 22 scales including 60-inch log log scales. Pickett aluminum slide rules were available with traditional (-T) white paint or Eye-Saver (-ES) 5600-angstrom yellow paint, optimized to relieve eye strain. The N500-ES pictured here has a convex cursor lens and was manufactured in 1962.

Available Scales: LL1+ LL1- A [B ST T S C] D DI K ||| LL2+ LL2- DF [CF CIF L CI C] D LL3+ LL3-

[View Detail]

Pickett N600-ES
 Pickett N600-ES

Best known as the slide rule of choice for NASA astronauts in the 1960s, the Pickett N600-ES is an advanced 5" pocket duplex log log slide rule with 22 scales including 30-inch log-log scales. Like other high end Pickett slide rules, the N600-ES features an aluminum construction and proprietary Eye-Saver (ES) yellow paint, with lithographically applied precision scales. Early examples of the N600-ES have the same set of scales as the N500-ES 10" hi-log slide rule, but later examples replace the CIF scale on the reverse of the slide with a Ln linear scale. This substitution has been criticized by users, as the removal of CIF breaks the six-scale multiplication/division capabilities of the N600.

The N600-ES was accepted into the U.S. space program without modification, and was carried into space on multiple Apollo missions, including Apollo 11 and Apollo 13.

Available Scales: LL1+ LL1- A [B ST T S C] D DI K ||| LL2+ LL2- DF [CF CIF L CI C] D LL3+ LL3- (CIF replaced with Ln in later examples)

[View Detail]

Pickett N803-ES
 Pickett N803-ES

The N803-ES is Pickett's most sophisticated standard-body slide rule: a log-log duplex slide rule with 28 10" scales, 80-inch dual base (base-10 and base-e) log log scales and double-length square/square root scales. The N803-ES pictured here was manufactured around 1959, and features Pickett's proprietary Eye-Saver (ES) yellow paint.

Available Scales: LL0+ LL0- LL1+ LL1- DF [CF CIF L CI C ]D LL2+ LL2- LL3+ LL3- ||| SqRt1 SqRt2 K A [B S ST T CI C ] D DI DFm

[View Detail]

Pickett 120 & 121-T
 Pickett 120 & 121-T

Devices included in this entry:

Pickett 120 Trainer 10" polyphase slide rule
Pickett Microline 121-T 10" polyphase slide rule (pictured in thumbnail)


In the 1960s, Pickett began manufacturing low-cost plastic student slide rules under the Microline brand name. Their first model was the 120 Trainer, introduced in 1964. The 120 Trainer is a 10" simplex polyphase slide rule with a non-reversible slide. Pickett later upgraded the 120 Trainer by adding conversion tables to the reverse side, creating the Microline 121-T. Early Microline slide rules have a 1.5" body and similar proportions to a Pickett aluminum slide rule, while later examples have a 1.9" body and a more robust cursor construction, and were available in white or Eye-Saver yellow variations.

Available Scales: K A [B T Cot S Cos CI C] D L (T/Cot and S/Cos reversed in later examples)

[View Detail]

UTO 601
 UTO 601

Distributed in the United States under the Hoffman brand name, the UTO 601 is a plastic 5" Rietz simplex slide rule with a reversible slide, similar in function to a Dietzgen or K&E polyphase slide rule but with a somewhat different scale arrangement and the addition of a ST extended sine scale. The UTO 601 also has a complex cursor with three ancillary hairlines, and a fixed hairline on the reverse for using S, ST and T scales without removing the slide.

The UTO 601 was sold exclusively as a branded promotional item, and can be found with many different company names stamped on its reverse. The example pictured here is a promotional item for Propellair, a defunct manufacturer of electric fans.

Available Scales: K A [B CI C] [S ST T] D L

[View Detail]

©2000-2017 The Vintage Technology Association. All rights reserved.