Horological Tools

The clock and watchmakers of the 18th century were active in deve-loping wonderful new tools to improve and ease their work. Those tools are documented by surviving tools and in early publications beginning with Moxon’s 17th century articles and books. One of my pet peeves occurs on occasion in front of a display of beautiful antique watches. A viewer makes a comment such as, “How did they make such beautiful objects with such crude tools?” I feel the need to respond with, “Their tools were not crude, often being equally ingenious, as beautiful and skillfully made as the watches themselves.” When fine antique horological tools are displayed along with the watches and clocks, the viewer can begin to appreciate how the marvelous watches were produced

More importantly the new tools of the eighteenth century evolved into many of the machine tools used today, now electronically controlled. A fine example is the wheel or gear cutting engine. Three hundred years ago devices with multiple moving parts were frequently termed engines. The earliest mention of a wheel cutting engine known to me appears in Robert Hooke’s diary of August 16, 1672. He writes, “Lancashire watchmaker’s son about wheel cutting engine.” I interpret this as the son telling Hooke how they cut gears in Lancashire. Nine months later Hooke wrote in his diary on March 18, 1673 “Began wheel cutting engine.” If watchmakers were using the wheel cutting engine in Lancashire, Hooke’s engine was not the first. Nicolas Bion in his 1709 book “Treatise of the Construction and Principal Uses of Instruments of Mathematics” presents the first illustration of the wheel cutting engine known to me. In the nineteenth century gear cutting engines modeled on those early engines were most important in building the machinery of the industrial revolution. The antique tools are part of industrial and art history.
Another wonderful machine tool is the screw cutting machine. In the horological field it has a special name: a fusee engine. Originally designed to cut the groove for the fusee chain in a clock or watch, it could equally well cut a uniform screw thread. The typical early German fusee engine had three right hand and three left hand lead screws with matching screw boxes. Probably the first illustration of a fusee engine appears in J.G. Leutmann’s German publication of 1717. Thread cutting on many 20th century screw cutting lathes still uses a lead screw and thread nut to cut screws, varying the lead by change gears driving the lead screw.
One has only to browse through the rare 18th and 19th century catalogues to see the attention and artistry the makers applied to the tools, both hand-held, bench and floor mounted. Fancy lattice and grill work, gold stripped on shining paint, statuesque curves were the fashion. Crude tools were the exception, and usually homemade by a tasteless worker.
The tools illustrated in this article prove the validity that the antique tools were both mechanical and visual works of art.

A wheel cutting engine made by Thomas Septhon circa 1760 in Prescot, England. Such a tool was used for cutting small watch wheels or gears. The large circular brass plate, a dividing plate, has a series of concentric rings with different numbers of holes drilled in each ring corresponding to the number of teeth desired in the watch wheel. The wheel to be cut is secured to the top of the same arbor upon which the dividing plate is fastened. The gear wheel rotates the same as the dividing plate as it is turned. The milling cutter, shaped to cut a proper tooth slot, is hand cranked by the gearing on the swinging frame. The long arm, an alidade, just above the dividing plate, locks the plate in position for cutting each tooth slot.

A unique and delightful fusee engine made in Ferdinand Berthoud’s shop and signed by him. Berthoud was the famous 18th century French marine chronometer designer-maker and author of several outstanding books on horology. A fusee is a somewhat cone shaped device for varying the torque of the mainspring input to the watch or clock gear train. The fusee is connected to the mainspring barrel by a small chain that beds in a spiral slot on the surface of the fusee. This tool cuts that spiral slot. The engine is a true work of art. Most likely it was for use in a royal workshop, perhaps for Louis XVI himself, who liked to putter in the shop. Note the beautiful sculpting of the knobs at the lower left end of the tool. Similar knobs are located at the other end.

Also at the left is a graceful termination of the slide plate. The right end of the plate is similarly ornate. The steel heads of the screws and pins are fancifully turned and blued. The tool has several adjustments to permit flexible use. An ornamented key to fit the several adjustment squares is at the lower right.

An elaborate 19th century gear driven Swiss fusee engine. The blank fusee to be cut shows near the top right of the machine. All the features of the most advanced design are included in the pictured engine. At the bottom middle of the illustration behind the large gear wheel can be seen a portion of the slot in the bar for adjusting the travel of the cutter. Turning the crank handle advances the cutter and rotates the fusee blank. The cutter is guided by a follower riding against a template mounted below the blank fusee to be cut. The lever which holds the cutter blade is seen near the right end of the tool.

Hand pressure on the lever forces the cutter into the brass fusee blank as it rotates, thereby making a cut. The cutter is shaped to give the desired final depth of cut. Poised above the blank fusee is a small milling cutter or fraise for cutting a notch in the fusee into which the hooked end of the fusee chain is anchored. All of these functions are adjustable, making the machine very versatile in use.

An 18th century clock wheel depthing tool. The proper meshing of a gear wheel and a pinion could be deter -mined by this gracefully designed tool. The spacing of the runners can be adjusted so that the wheel and pi-nion when rotated felt smooth and proper to the crafts -man. He could then transfer that spacing to a clock plate using the points of the runners for a marking compass centered on an existing pivot hole. The new pivot hole could then be drilled on that mark.

A complex Swiss clock pinion cutter of the 19th century. The steel and brass tool is well designed, with four notched dividing plates of 12, 14, 16, and 20 divisions. There is a decorative small steel cup at the top of the machine holding the oil used for lubricating and cooling the cutting blade. For centering the cutting blade or saw, the vertical shaft supporting the oil cup can be screwed down to the blade. The pointer at the bottom end of that shaft is formed in the shape of a sculpted acorn. The cutter arbor is driven by a cord from an external power source, possibly a foot or hand wheel. The wooden crank handle at the left end, when turned, drives the pinion blank into the rotating cutter blade. The knurled adjusting screw heads supporting the cutter arbor and their locking nuts are attractively formed, showing the esthetic taste of the tool maker.

Dr. Theodore Crom

Is a retired structural engineer-contractor with an honorary Doctor of Engineering degree from the University of Maryland. He is a Silver Star Fellow of NAWCC, a British Horological Institute Fellow, and a Barrett Silver Medal awardee, in addition to being a member of numerous horological associations worldwide. He is also the author of s eve ral books, including “Horological Wheel Cutting Engines 1700-1900”; “Horological Shop Tools 170 0 - 1 9 0 0 ” ; “Horological and Other Shop Tools 1700 to 1900”; and “Early Lancashire Tools & Their Makers”, among others. For additional information, please contact: