REVIEW: Penman: Gear Cutting on the Lathe

  • Thread starter Fortunat Mueller-Maerki
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Fortunat Mueller-Maerki

NAWCC Star Fellow
NAWCC Life Member
NAWCC Fellow
Sep 23, 2001

New Edition of a ‘How to..’ Manual for Gear Cutting

Gear Cutting on the Lathe. By Laurie Penman. Forth edition published 2010 by the author. ISBN: 0 907868 22 3. 72 pages, 21 cm x 15 cm, paperback, 41 black and white line illustrations. Available from the author by -emailing for $16.00 (incl. shipping and handling)

The British engineer Laurie Penman, who became a self-taught clock repairer in the 1970s, and started writing practical advice books on the subject in the mid 1980s is probably best known in the USA for becoming the clock instructor at the American Watch and Clockmakers Institute when he emigrated to America in 2001 at the age of 69. He had been running a correspondence course in clock repair in the USA since 1990 (operating under the AWCI clockmakers correspondence course label while he was in their employ), and in 2010 he moved back to England. .In 1999 he first published his module on horological gear cutting as a small stand alone publication of 51 pages.

The book under review is the2010 4th edition of this book. I it had reportedly been out of print for a few years (but curiously an earlier edition, i.e. the 2nd or 3rd, with 84 pages, is still available from the print-on-demand publisher as I am writing this review). Thumbing through the first and fourth editions side by side it is hard to find the few minor content revisions that seem to have been made. The cover now has a photographic illustration rather than a line drawing, and all 41 images (line drawings) are now spread throughout the text, while before they were on separate pages; the illustrations have been renumbered.

But essentially this “new” edition still is an offprint of the old correspondence course materials the author first developed in the 1980s. It is a step by step description on how to cut a gearwheel, focussing on making a replacement for a broken wheel, using the old wheel as you dividing template. The text also covers related subjects such a how to make a tooth form cutter, and provides suggestions for sources of related material (although –judgeing from the scarcity of email adresses and websites quoted – I wonder how updated that information is). This linear, unstructures approch makes the material hard to use for anything else than linearly reading straight through “the lesson.” There are no chapters, no table of content, no index, so finding anything in the publication is tedious. The text is solely relevant to clock repairers, and is not applicable to watch related work.

Unfortunately there are virtually no alternative publications available describing gear cutting from a horological perspective. In principle cutting a gear on a lathe is theoretically not a complex process, but in reality this is a task that is hard to do well and efficiently. The details and the hidden pitfalls of the process vary enormously depending on exactly what equipment and what raw material you use, as well as on the operators experience in machining metal parts. . Penman’s linear text may be a useful introduction to the subject. But in the end –as far as this reviewer s concerned- you can only learn horological gear cutting through constant practice, which is why even most professional watch and clock repairers ‘farm-out’ these tasks to specialists who have more experience (and better equipment) to tackle these issues.

Given the scarcity of alternative titles this small booklet may be a useful title to acquire if you want to try to cut a clock wheel on a lathe, but ultimately the reader may be better served with a more general and more in-depth textbook on lathe skills. In the opinion of this reviewer an easy to follow introductory publication to the subject, for a general clock enthusiast audience, hopefully using many and good close-up photographic illustrations (rather than the technical drawings favored by Penman) still awaits to be written.

Fortunat Mueller-Maerki, Sussex NJ April 2011

Richard Watkins

NAWCC Fellow
May 2, 2004
Another book is Wild "Wheel and Pinion Cutting in Horology", 2001, 253 pp, 555 and 11 ill.

The contents is:

11 chapters. The first 4 chapters (58 pages) survey wheel and pinion cutting tools and chapter 5 (8 pages) summarises the theory of cycloidal gears.
Then chapters 6 (29 pages) and 7 (25 pages) give detailed instructions for wheel and pinion cutting respectively, and chapter 8 (20 pages) discusses the form of cutters and how to make them.
The last 3 chapters consider related topics: crossing out and mounting wheels (21 pages), finishing and replacing pivots (11 pages) and miscellaneous operations (45 pages on depthing, calendar wheels, racks and snails, count wheels, Geneva stop work, escape wheels, calculating missing components, and workshops).
There are 7 appendices giving Swiss and British standards, lantern pinion data, specifications of Carpano cutters, dimensions of wheel and pinion cutters, and pendulum lengths. There are also a list of suppliers, bibliography and index.
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