Roubo’s ‘Fathom’ Reborn


I always felt odd building French workbenches using English (or worse) inches.

Anyone who has studied the history of measurement knows that there are as many systems of measurement out there as there are cultures and epochs. Surprisingly, many of them are similar because they are based on the human form. But they are all a little different.

Rather than whitewash these differences or convert them to metric, I try to incorporate them into my work in the same way you would never put a Roman ovolo on a Grecian piece.

At the vanguard of this curious approach is Brendan Gaffney, a woodworker and musical savant who has been taking a deep dive into alternative measurement systems. He recently made three rulers for sale based on Japanese, Roman and Egyptian systems. I purchased the Roman ruler and it is a work of great beauty. I plan to use it in constructing two upcoming Roman workbenches.

And now Brendan is exploring the 18th-century French measurement system.


After some back and forth, Brendan has constructed French “fathoms” that are based on A.J. Roubo’s plate 100 from “l’Art du menuisier.” Here’s Roubo’s description of the fathom:

“Woodworkers use fathoms as the fundamental unit for taking their measures. This is nothing other than a ruler of 6 feet in length divided into feet and one of these divisions into thumbs so as to be able to know how far each part they are measuring is in length. There are those who do not use fathoms but simply use a ruler of whatever length on which they mark their measurements.”

Brendan’s version, which goes on sale on Saturday, is faithful to that description. His fathom is made from flame maple, planed true, hand-marked and finished in Brendan’s workshop. If they are anything like his other rulers, they will be spectacular.

Do you need a fathom? No. You can make your own if you think you need one. But if you’d like to support a fellow explorer who is diving deep into waters that have been uncharted for more than 200 years, you can do that here.

I’m ordering one for layout work and to help interpret the drawings from our forthcoming book “Roubo on Furniture,” which contains lots of scaled drawings.

— Christopher Schwarz

About Lost Art Press

Publisher of woodworking books and videos specializing in hand tool techniques.
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9 Responses to Roubo’s ‘Fathom’ Reborn

  1. artisandcw says:

    Yowser. I’ll be ordering mine as soon as I can remember where I left my wallet.

  2. Hey Chris, thanks so much for your kind words. I’ve put them up on sale now, in celebration- so anyone can head over and get one now!

  3. charlie says:

    Fathom is from Middle English fadme, from Old English fæthm “outstretched arms.” So another bodily part to add that to your feet and thumb measurements.

  4. “I always felt odd building French workbenches using English (or worse) inches.”

    Nowt wrong with English inches. Width of hand = 4″, spread of hand = 6″.

    From Wikipedia, the free encyclopaedia

    A fathom = 6 feet or 1.8288 metres, is a unit of length in the old imperial and the U.S. customary systems, used especially for measuring the depth of water.

    There are two yards (6 feet) in an imperial fathom.[1] Originally based on the distance between a man’s outstretched arms, the size of a fathom has varied slightly depending on whether it was defined as a thousandth of an (Admiralty) nautical mile or as a multiple of the imperial yard. Formerly, the term was used for any of several units of length varying around 5–5 1⁄2 feet (1.5–1.7 m).

    The name derives from the Old English word fæðm, corresponding to the Old High German word “fadum” meaning embracing arms or a pair of outstretched arms.[2][3][4][5] In Middle English it was fathme. A cable length, based on the length of a ship’s cable, has been variously reckoned as equal to 100 or 120 fathoms. At one time, a quarter meant one-fourth of a fathom.

  5. momist says:

    So, if a French fathom is six feet, and measures a modern 6′ 5″, then the French foot (or was it only the King’s?) was nearly an inch longer than an English one. How come? Why were there twelve thumbs (pouce) to the foot? (My feet have ten toes). Did the King also have longer thumbs?
    Questions, questions . . .
    Maybe the answers lie in the origins of the English measures.

  6. Damien says:

    Besides the toise of six feet the French also used a less outstretched ‘brasse’ ( bras=arms) of five feet

  7. Jim Eckman says:

    Fathom is certainly a cool word…
    “Full fathom five thy father lies”

  8. The Pied du Roi goes back upon the times of Charles the Great. I have used it to make French “Voboam” baroque guitars and it works great.

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