Threads in Wood

Chronicle of the Early American Industries Association, Inc., The, Jun 2003 by Packham, Jim

Everyone interested in early tools is familiar with the classic carpenter's clamp (Figure 1). Turning the threaded spindles closed the jaws so that the carpenter could clamp together pieces of wood to be glued or otherwise fastened. Less familiar are some of the other tools that have wooden threads. Examples would include bookbinders' plows, or coopers' compasses.

This article will identify many of the traditional tools that have wooden threads. There also will be some historical notes about the helical screw and a review of the main methods for making threads in wood.

Historical Notes

It is not clear when the first application of the helical screw occurred or what that application was. It probably was in the Middle East at least 300 B.C. One of the earliest references is found in a mathematical treatise by Archimedes (287-212 B.C.). He explained the mechanical principle of the screw as a form of wedge, and he set out the mathematical characteristics of the helix. Archimedes also described (and possibly invented) the water screw for raising water for irrigation purposes.

By the time of Archimedes, it is likely that screws of wood already were being used for vises and for fruit presses. Figure 2 shows a modern reproduction of a wooden screw vise (center right) in an Etruscan stone carvers' shop. It was photographed in the Etruscan Museum at Volterra, Italy. Most of what is known about the Etruscan society (700-200 B.C.) comes from stone carvings found at burial sites. A memorial to a prominent stone carver is the basis for the museum's reproduction.

The earliest known record of the use of helical screws for fruit presses is found in the writings of the Roman author Pliny (first century A.D.). But screw presses probably were in use several centuries earlier, replacing simple lever presses for olives, or for grapes. The design of such presses did not change significantly for centuries (Figure 3).

The largest tool with a wooden screw known to the author is a lever-and-screw style of cider press that was used at Jordan, Ontario, in the nineteenth century. The screw itself still can be seen at the Jordan Museum. It is made of hickory about 16 inches in diameter and about 10 feet in length. Making this cider press screw is reported to have been a whole winter's work by a carpenter in southern Pennsylvania. In the spring of 1830, it was transported to Ontario by ox wagon.

Most applications of threads in wood arc found in hand tools made prior to the mid-twentieth century. However, there are a few other applications. A favorite project for some wood turners is making beautiful, round, wooden jewelry boxes with threaded tops.

Some items of furniture have used wooden screws to facilitate adjustment or assembly and disassembly. Examples would include the legs of some small tables, the tilt and clamp part of "cheval" mirrors, and the adjustable candle stands of the eighteenth century (Figure 4).

An unusual application of wooden threads was in the construction of the "rope" bed up to about the middle of the nineteenth century. The round, wooden side rails of these beds had right-handed threads at one end and left-handed threads at the other. Assembling the rails to the head- and foot-boards then was simply a matter of turning the rails into threaded holes in the end boards. More information on this application can be found in the author's article on left-handed screw threads in the September 1992 issue of The Chronicle.1 Tom Kclleher's article, "Nuts and Bolts" in the September 2002 issue of The Chronicle provides a good review of the history of threads in metals.2

Tools with Wooden Threads

This section will illustrate and briefly describe the variety of tools that have wooden threads as an integral part of the tool. In most of these tool applications, the screw is used to create pressure; sometimes it is used to adjust the position of part of the tool, and sometimes it is used to do both. Each illustration includes information on approximate tool size in terms of: maximum overall size in inches, length of screw thread in inches, nominal screw diameter in indies, and number of threads per inch.

A reproduction of an eighteenth-century wine press (Figure 6) can be seen at Colonial Williamsburg. It has a massive frame and is turned downward to squeeze the juice from grapes held in trays.

Although screw clamps (Figure 6) usually were made with tightly grained hardwood such as beech, fruitwood, white oak, etc. the threads can break easily with too much pressure.

A cabinet maker or joiner would need many sets of clamps and therefore might have one or two sizes of screw box and tap (as shown in Figure 6) in his tool box so that he could make replacement clamps whenever needed.

By the early 1800s, sets of manufactured clamps also could be purchased from local tool and hardware suppliers. By the early 1900s, the Jorgensen patent clamp with its steel screws was beginning to supersede the classic wooden screw clamp. It usually is assumed that when a miter clamp (Figure 7) is used to make the forty-five-degree angle on picture frames, the craftsman used a block plane. But some tool historians have argued that a broad-bladed chisel was used. In either case, the clamp frame was not supposed to be touched by the cutting tool.