The types of sliderule can be broadly broken into 5 main categories.

 

An additional type could also be added to the list although strictly a variation of the Disc type rules.

 

The category would be "Pocket Watch Calculators"

 

 

Descriptions of these types plus examples appear below

 

 

This is the most common type of rule and features scales predominantly on one side and has a single sided (one window) cursor. On many rules scales were included on both sides of the slide and would be indexed (ie able to be read in conjunction with the scales on the front of the rule) by markers in windows on the rear of the slide.

The most common examples of this type of rule would be the Faber Castell 1/54 and 1/87 and the Aristo 915.

 

Duplex models feature scales on both sides of the rule, with a dual-faced cursor that can relate each scale on each side to another. This greatly increased the number of scales that could be used on the rule. High end examples include the Post Versalog, K&E Decilon, Aristo 969, Hemmi 255, Faber Castell 2/83 and the W&G 432

 

 

 

 

These rules had scales laid out on a disc in a circular or spiral fashion. The advantage was that longer scales in a more compact design could be formed. And in addition to this the scales could function in a continuous way as opposed to the linear examples where if the result was past the end of the index the slide had to be reset.

Common examples of this type are the Concise 300 and the Faber Castell 8/10.

 

 

This type of slide rule is a version of the Disc rules but the faces are usually encased behind glass and they resemble pocket watches, hence the style name. Many of them where extremely well made similar to a very good quality time piece and they are sought after by collectors. The main examples of this type would be the Fowler cacluators and the one shown below the Halden Calculex. 

 

 

This type of slide rule is one of the most sought after types by slide rule collectors. It is a cylinder shaped rule with a spiral scales wound around the exterior of the cylinder. The advantage of this construction was that it offered a very long scale in a compact shape. Some scales could be as long as 50 feet. Which allowed slide rule calculations to be performed with 4 to 5 digit precision..

Common examples would be the Otis King and the Fuller slide rules.

 

 

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Another type of cylindrical rule are the barrel rules. These devices are a cylinder with scale segments arranged around the periphery of the cylinder and similar scale segments arranged in a cage like fashion around the exterior of the cylinder on a separate support. Again the advantage was a longer scale offering greater precision in calculations