• 455 Martinson, Los Angeles
  • 8 (043) 567 - 89 - 30
  • support@email.com
  • Unusual non-logarithmic squaring desktop QR 41 model by Dennert & Pape (D&P)
  • Colour combinations slide rule for Interior Designers
  • Professor Fuller’s Drum Calculator from 1878 - made by W.F. Stanley
  • Modern Kienzle wristwatch with slide rule bezel calculator
  • Ruxton Multi-Vider drop-lead pencil & slide rule
  • Rare Otis King Model N for Retail & Monetary with white scales (422 & 424) on a black background
  • Darnley’s Rotable Lightning Calculator/Pencil Case
  • Design for this Antenna Radar Beam Pattern Detection slide rule was classified during WWII by UK & US governments - made by Lawrence
  • Makeba Kombinator pencil & slide rule
  • Rare Carbic-made Fischer Calculator
  • Specialist slide rule for a national home cable radio broadcasting system offered in The Netherlands in the 1900s
  • Smallest drum (≈ 2.4m) made by LOGA

A man must have a hobby….


This non-commercial website was an amazing 60th birthday present from Ros. But the website name is thanks to another family member - our daughter Siân. When asked as a teenager what I did, she often told her friends: “My Dad? Oh, he collects expensive sticks of wood!”

When the latest PC/tablet is out-of-date inside 6 months, it may come as a surprise that the Englishman in the image, the Rev. William Oughtred (1575-1660), invented a calculator around 1621 that would be in continual daily use for nigh on the next 400 years. My hobby is collecting and writing about this analogue calculating wonder - the SLIDE RULE. The analogue concept behind the slide rule was successfully adopted and adapted by many trades and professions. Remarkably being able to use such an elegant analogue instrument from a bygone age is still a licensing condition for all private and commercial pilots.

This site is a virtual “display cabinet” for my collection (as it gets uploaded) of slide rules, slide charts and the odd mechanical calculating aid plus a “bookshelf” for my published articles - enjoy browsing.

The history - how it all began ....


To learn more about the history of this calculating wonder check out the “Slide Rule History” by the Oughtred Society (OS) or my 2-page summary (in Dutch!).

Anyone needing a “memory jogger” or is just intrigued how such analogue calculators of the past worked, the International Slide Rule Museum has a richly illustrated “How To Use The Slide Rule” teach yourself course or download a self-running 35mm “diafilm” Introduction Course with synchronised audio I digitalised. Afterwards try out some test calculations with Robert Wolf's online simulation of the classic Nestler 23R wooden slide rule. If all this gets you thinking about starting your own collection then the UKSRC/OSBeginner’s Guide to Collecting Slide Rules” is a must read.

For any educators looking for maths related inspiration & teaching aids/material then you need to look no further than Nicola Marras’ website. But if you are just looking for reference books/publications on slide rules try one of these: List 1 or List 2.

Latest additions


Slide Rules

A.W. Faber-Castell, 66/92, Pocket Log-Log, L, Closed/solid frame, celluloid

Tech Papers

Keeping in Rhythm

Proceedings IM2021

news - So far 1198 rules are loaded from my collection

27 October 2021


HEMMI with its sunburst logo is a highly respected Japanese maker of slide rules. The company has a rich history – operating from 1895-1975. HEMMI chose to make most of their models from bamboo with celluloid veneers. An understandable choice as bamboo was better suited to the humid conditions of their “home market”: Asia. They sold an impressive range of models - many with usual scale layouts. Click HERE to see the ones I have – including two models that each need 4 cursors to work!

17 September 2021


Issue 21 of the UKSRC Gazette is another bumper edition - 162 pages & more than 20 in-depth articles. As ever, this non-profit publication is excellent value & there is even a modestly priced PDF version for parts of the world were postage costs are high. Use this link to order your copy.

08 December 2020


Premièred at the December 6th UKSRC Zoom meeting the popular book by Peter Holland on the slide rules made by A.W. Faber and A.W. Faber-Castell has gone digital. The 8th Edition is now free to download from HERE …

01 August 2020


Did you know a special model exists for each house of Hogwarts School of Witchcraft & Wizardry? Depending on your Gryffindor, Ravenclaw, Hufflepuff or Slytherin affiliations select your Harry Potter inspired sorcerous slide rule simulation from Robert Wolf’s website ...

24 May 2020


A milestone I expected to reach earlier. It takes ages to catalogue & capture conscientiously all the details. The upside is that I am learning a lot about my collection! The1000th entry was fittingly an unusual & extremely rare KLOOS disc for heavy-duty steel constructions 

13 May 2020

STOP PRESS: new book

ALRO expert Otto van Poelje has published: The ALRO Catalogue. This Dutch maker is famous for circular models where the lid doubles as a desk stand. The 200+ page hardback book has every calculating disc, slide rule & slide chart they ever made - all meticulously catalogued & photographed. Attractively priced at Euro 35 order your copy online HERE ...

01 October 2019


Generically a slide rule can solve complex calculations but CANNOT do simple arithmetic. A rare and unusual exception is the newest addition to the collection - a System Korte slide rule that CAN add and subtract!

09 May 2018

Amazing Digital Slide Rule

Ace Hoffman has developed an awesome simulation of a linear, round, concentric and drum slide rule. From Ace's Homepage download a function-rich version for your phone, tablet or desktop.

02 February 2017


Lawrence made the only known slide rule considered so vital to the WWII effort that the UK & US governments had it classified - based on research from MIT it calculated radar antenna beam patterns, beam width, gain, etc.

My wish list

Sought after slide rules still missing from the collection:
A.W. Faber-Castell8/13, 8/14, 8/15 & 51/88
Addiator GmbHOctadat
AHREND (Wed. J. Ahrend & Zoon)642T, 649, 651, 690, 696, 698, 699 & 701
Albert MartzCursor for pocket System Frank
AWF (Ausschuss fuer Wirtschaftliche Fertigung)SR703, SR705-709, & SR754
Controller Calculator KG200 R
DARGUE Bros. Ltd. / SimplonSub-Ivory SR-1 & SR-4 + Honduras SD10, WR-2A, WR-5 & WR-7
Engineering Instruments Inc.Either circular “vinylite” model
Fearns CalculatorsBarber Shop Harmony Calculator
FowlerNautical, Artillery, Kearns & Mackay
ITAB (Internationaler Tabellenverlag)Multicalor Flachheizkorper & Styropor-Vollwarmeschutz
IWA – F. Riehle GmbH & Co KG15489 Harmonik
Johann Faber180/080, 180/082, 9203, 9204 & 9204
Keuffel & Esser (K&E)4081-3 Braille version
KOSMOSBook: "De Rekenliniaal" - 11th & 12th Editions
L&C Hardtmuth / Classic10" Series III
Lawrence Engineering ServicesS-M (C.V. Ore) & Exposure (MIT)
LOGATF, T150, T300, O2, Terminator & Baumaan lighting
NestlerCursor/runner for 24b (100cm), RP 75, Kreisrechner & Disc-O-Lator
S.R.&S.E. (Slide Rule & Scale Eng. Co.)- any -
Systeem Matthijssen- any -
UniqueNorman, Perfectus, Dial & Junior