Threads in Wood
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.
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.
The luthier’s clamp (Figure 8) is just one of several screw clamps of unusual shape used in making string instruments. Up to a dozen of these particular clamps would be used when gluing up the body of a cello or a bass viol.
Most carpenters’ benches of the eighteenth and nineteenth centuries were equipped with vises operated by a wooden screw (Figure 9). In addition, there were small supplementary vises (Figure 10) for mounting in the main bench vise. These were used for wood carving or for model making.
Traditional bookbinding included three tools that have threads in wood. On the stitching frame (Figure 11 ), sewing cords are tied from the cross bar to pins under the table, and then are stretched by turning the threaded nuts under the cross bar. Then each folded sheet of the book is sewn to the stretched cords. (A very similar application of screw threads was used in the stretchers for tambour and tapestry frames, except that the stretching was applied to both directions of the canvas yarns.)
After the spine of the hook is completely sewn, it is shaped and glued hefore cutting the pages to a consistent edge. The book is clamped in a laying press (Figure 12), and each of the three open edges is trimmed with a bookbinder’s plow (Figure 13). One arm of the plow runs in the laying press guide. The two-sided blade cuts a few pages with each back and forth movement of the plow in the guide. After each pass, the blade is advanced slightly by turning the screw, ready to cut a few more pages.
Note the decorative finials on both the stitching frame and the plow. These tools were made about 1830 by Hampson & Bettridge of London. The laying press has a somewhat plainer design and was made about 1850 by W.O. Hickok of Harrisburg, Pennsylvania. This latter firm is still in business.
There are two tools used in making textiles by hand that include wooden screws. The spinning wheel of Figure 14 is much smaller than usual, but it has a typical tensioning mechanism. At the left end of the slanting table is the knob of the tension screw. It adjusts the position of the flyer/bobbin assembly relative to the drive wheel. Proper tension on the drive cord is necessary for good spinning. Figure 15 is a tension screw from a spinning wheel of more conventional sixe. It is included to show the standard shape of this part.
The click reel (Figure 16) is a measuring tool, used to wind amounts of yarn after spinning. This reel has a circumference of two yards and a forty-to-one worm gear reducer such that a click is heard after forty turns of the reel. This quantity of yarn-eighty yards-some-times is called a “knot.” In the click reel, the wooden screw acts as a continuous wedge turning the worm gear. It is one of the most unusual applications of threads in wood.
Most wooden screws have a sixty-degree thread angle. This is a very good thread angle for most applications in tools. It also is suitable for the worm in a click reel. But if a worm gear is to transmit mechanical power, it should be a metal worm having a thread angle of about thirty degrees.
Figure 17 shows an old tool that was helpful in caring for textiles. Table and bed linens were smoothed out in this late-eighteenth-century linen press. Again, there are decorative touches that complement the quality of the tool.
The mallet handle of Figure 18 has been backed out enough to show a taper just behind the threading. When the handle is screwed in fully, this taper wedges the handle very firmly into the head. It is an effective solution to the old problem of loose mallet heads.
Other tools in which a wooden handle is fastened to a working head by means of wooden threads would include long-handled brushes, mops, and push brooms. The traditional push broom was made with two threaded holes for the handle. When the bristles acquired a lot of bend in one direction, the handle could be moved to the opposite hole. Tools with screw-mounted handles also made it easy to replace a broken handle, or to use the same handle with more than one tool.
You would be more likely to find a wooden nutcracker (Figure 19) in a souvenir shop than in an antique tool auction. Hut it is a working tool.
Two different marking gauges make use of threads in wood (Figure 20). In one, the two threaded nuts are clamped together to position the guide. In the other, a wooden thumbscrew holds the guide in place.
Several types of woodworking planes utilized wooden screws. Adjustment of the fence position for plow planes was provided in several ways, of which the use of two screw arms (Figure 21) is perhaps the most common method.
At the top of this plane’s body, one can see a brass adjustment screw used to change the position of the plane’s depth guide. Another brass screw (not visible) was threaded into the side of the wooden body to clamp the position of the depth guide. This brass thumbscrew has a 1/4-inch diameter with 20 threads per inch. The beech plane body was tapped directly to receive this thumbscrew. However, such finely pitched threads normally are too weak in wood, and they have broken with use in this plane. But they were another application of threads in wood.
A moving, or adjustable, sash plane was used to cut the inside moulding and the rabbet in one pass. It usually was made with two plane irons in one body, but sometimes it was put together from two separate moulding’ planes, spaced apart by a shim and clamped together with wooden bolts and nuts such as in Figure 22.
The adjustable founding plane (Figure 23) sometimes is called a witchet. It was used to turn square stock into a roughly round shape such as in making shovel or rake handles. Most rounding planes were handmade, but this one is imprinted SUMMERS VARVILL, one of the Varvill family of planemakers in York, England. This rounder has a nicely shaped brass wear sleeve.
Coopers used several tools that were unique to their trade. One of these was the croze plane. The use of three screw stems to adjust the position of the croze cut was characteristic of croze planes (Figure 24) made in Europe. This croze plane has two nicker blades and a square croze blade, indicating that it was intended for making beer casks. This plane has decorative carving, is dated 1848, and has several indications of having been made by J. Augustin, a well-known planemaker in nineteenth-century Vienna.
The center wheel plow plane (Figure 25) uses threads in wood in a special way. The screw arm has right-handed threads on one side of the brass wheel and left-handed threads on the other. The combination of right-hand and left-hand threads converts the circular motion of the center wheel to the linear motion required for the fence adjustment.
Two other tools have this combination of right-hand and left-hand threads. The hat stretcher (Figure 26) can be made smaller or larger simply by turning the centerpiece.
The cooper’s compass (Figure 27) also is adjusted by means of a cross bar with right-hand and left-hand wooden threads. A compass setting that can be “walked” around the croze exactly six times, gives the correct radius for the circle for the cask head. Some French coopers used this kind of bow compass rather than the common hinged compass.
Right or Left?
Except for the last three tools that have right- and left-handed wooden threads in combination, all the other tools have right-handed threads. This raises the question, why right? Why not left? It is a question that applies also to threads in metal, such as bolts and nuts and screw fasteners.
In my 1992 article on left-handed screw threads, I wrote as follows:
It is interesting to speculate why most screw threads are dextral and only a relatively small number are sinistral threads. The choice developed in the unrecorded past and no completely persuasive explanation seems to exist. It has been argued that tightening a right-hand thread wood screw is physically easier for the majority who are right-handed.3
This claim of an advantage in turning right-handed screws can be found in The Ambidextrous Universe by Martin Gardiner.4 He poses the question, “Can you think of any reason why it is a universal convention throughout the world for screws and bolts (except those used for special purposes) to have right-handed threads?” Gardiner’s answer is as follows:
The right-handedness of screw and bolt threads reflects the dominant right-handedness of the human race. If you hold a screwdriver in your right hand, a stronger twisting force can be exerted clockwise than counterclockwise because it brings the powerful bicep muscle of the arm into play. In addition, the fleshy base of the right thumb applies greater frictional resistance to a screwdriver handle when it is twisted clockwise. (I am indebted to Dr. Henry Kopell of the New York University of medicine for calling both points to my attention.)5
Even though a right-handed person may have a physical advantage in driving right-handed screws with a screwdriver, this does not seem to be an adequate explanation for the long-standing preference for dextral threads.
In a recent book, Witold Rybczynski offers a thorough history of the screwdriver and screws.6 He does not address the question of the human preference for the right-handed helix. But he does conclude that the screwdriver as a tool to drive slot head screws and bolts was not developed until the fifteenth century and that it was an uncommon tool until the nineteenth century.
However, screw fasteners, and a wide variety of other devices that use the principle of the helical screw, were used long before the fifteenth century. For example, screw bolts and nuts are known from the Roman era (they have square heads to be turned with a wrench). The earlier wooden screws for olive and grape presses and the later devices such as augers and letterpresses are all based on the principle of the screw and precede the use of the screwdriver. But they mostly have right-handed helices (for example, see Figure 3).
One of the earliest books about blacksmithing was written late in the seventeenth century by Joseph Moxon of England.7 He does not refer to wood screws or screwdrivers, but he does describe in detail the tools and techniques for a blacksmith to thread nuts and bolts. In part, he says, “… take the handle of the screw plate in your right hand, and lay that hole upon the screw-pin, and press it very hard down over it, and turn the screw plate evenly about with its handle towards you, from the right towards the left hand…”
This clearly describes making a bolt with a righthanded helix. It can be inferred that, by 1700, Moxon treated the right-handed screw as an established norm.
The preference for dextral threads certainly goes back to the unrecorded past. The choice may be linked to the human preference for clockwise rotation-itself perhaps related to the direction of sundial shadow. But there still is no persuasive explanation for the choice of right versus left.
Making Threads in Wood
There have been four basic methods of making threads in wood. Originally, making a wooden screw required the painstaking task of cutting a helix with a saw and then forming the threads with a chisel. Pappus of Alexandria, a fourth-century mathematician, recorded a very good method for laying out such threads. A template in the shape of a narrow right-angle triangle is wrapped around the cylinder to be threaded, and the hypotenuse of the triangle forms the line of the helix.
An engraving (Figure 28) from the eighteenth-century book, Manuel du Tourneur, by L.E. Kergeron illustrates well the “cut and chisel” method. The wine press screw of Figure 3 clearly was made this way.
By the time continuous motion lathes were available, threads in wood (and ivory and soft metals) could be cut with hand-held chasers (Figure 29). It is not known when this technique was developed, but it is described in L’Art de Tourner by Charles Plumier.8 He includes engravings of chasing chisels. A much better description of thread chasing is given in the recent book Making Screw Threads in Wood by Fred Holder.9
The earliest known reference to the screw box and tap also is found in the 1749 edition of Plumier. He describes and illustrates the construction of the tap (Figure 30), which then is used first to cut the guide threads in the matching screw box, and thereafter to cut internal threads that matched the external threads cut by the screw box. To Plumier, the screw box and tap were accessory tools for wood turning and provided an (easier?) alternative to hand-chasing.
Holtzapffel’s Construction, Action and Application of Cutting Tools, Volume II, contains a very thorough and detailed description of the design, construction and use of the screw box and tap for making threads in wood.10 These rather specialized tools probably were the main method for making wooden screws during the eighteenth and nineteenth centuries. Figure 31 shows the two main styles of tap for making internal threads in wood.
Figure 32 shows the parts of a typical screw box, as used for making external threads in wood. More detail on the design and construction of these tools can be found in the author’s article, “The Screw Box and Tap,” in the March 1987 issue of The Chronicle.11
Some screw box and tap sets were handmade by their users, but edge-tool manufacturers in Britain and continental Europe were offering sets of boxes and taps by the first quarter of the nineteenth century. A typical edge-tool catalog would include fifteen to twenty sizes, usually ranging from 3/8 to 3 inches in nominal thread diameter.
Although many edge-tool firms offered screw box and tap sets for sale, there is considerable evidence that only a few firms actually made these tools. The other firms arranged to have their brand name imprinted.
There is no record of any toolmaker in North America making screw boxes and taps in the eighteenth or nineteenth centuries. All were imported from overseas. A few sizes were made for hobbyists during the last quarter of the twentieth century by Conover Woodcraft of Parkman, Ohio.
Figures 33 a and b contrast the smallest and largest box and tap sets known to the author. The little set is for 1/4-inch threads and the large set is for 3 1/4-inch threads.
The box of the 1/4-inch size is 3 inches long, while the 3 1/4-inch size box is 18 inches long (including handles). The 1/4-inch tap weighs just two-thirds of an ounce, while the 3 1/4-inch tap weighs eight and three-quarters pounds-it is about two hundred times as heavy! The small tap can be turned easily with one hand, while the large tap requires two men using a steel bar about six feet long.
Despite the commonplace use of screw boxes and taps for over two hundred years, they also had some problems. The first problem came from the absence of size standards. Kven when a tap and box set was marked, say as 7/8-inch diameter, it could be as much as plus or minus 1/16 inch oft from its nominal size. In addition, there was considerable variation in thread pitch from one maker to another. For example, 5/8 inch diameter screw boxes exist with at least six different thread pitches from 5 1/2 to 9 threads per inch. One suspects that makers of screw boxes and taps were guided almost entirely by trial and error, plus personal preferences. The variations in sizes meant that if either of a matching box and tap were lost, it was almost impossible to find a suitable replacement. In turn, it is very difficult for collectors of antique tools to find a tap and box of the right size to repair say, an old plow plane.
Despite these variable aspects of sizing, the pattern of average pitch for a given nominal diameter based on over two hundred old tools-shows (Figure 34) an interesting relationship. For comparison, the International Standards Organisation (ISO) standard for coarse threads for metal bolts is shown also. The resultant curves are remarkably similar.
A second problem arises with the larger sizes of screw boxes and taps. For threads in wood larger than about one-inch nominal diameter, it is difficult to avoid incorrect threading, especially at the start of the helix. The threads may be askew, chipped, or at multiples of the intended pitch. To reduce such problems, there have keen several kinds of jigs devised for use with screw boxes and taps. For a review of these devices, see the author’s article, “Threading Gins,” in the December 2001 issue of The Chronicle.12
The development of the screw-cutting lathe in the late 1700s and early 1800s changed dramatically the way in which screw threads were made. This was a major technological step for threads in metal, but it also began to change how threads in wood were made. By at least the 1840s, some planemakers were using screw-cutting lathes to make the screw arms for plough planes. By about the 1860s, a major maker of carpenters’ screw clamps, Rufus Bliss of Pawtucket, Rhode Island, was using a screw-cutting lathe for his clamps.
The availability of small power routers and suitable jigs has given modern woodworkers a practical alternative to the screw-cutting lathe and to the screw box and tap set. But for a long time, a cabinetmaker, joiner, or toolmaker who wanted some threads in wood, would have depended on the screw box and tap.
Figure 3/5 shows a final example of a tool with wooden threads. This is, itself, a screw box that has wooden screw bolts to assemble the bottom block to the main body.
There are a few examples of wooden threads in furniture, but by far, most applications were as components of tools. So for several hundred years, screw boxes and taps were tools to make other tools having threads in wood.
1. Jim Packham, “Rope Bed Rails and Other Sinistral Devices,” The Chronicle 45, no. 3 (1992): 70-77.
2. Tom Kelleher, “Nuts and Bolts,” The Chronicle., 55, no. 3 (2002): 112-115.
3. Packham, “Rope Bed Rails,” 76-77.
4. Martin Gardiner, The Ambidextrous Universe (New York: Penguin Books, 1979), 20.
5. Gardiner, Ambidextrous Universe, 276.
6. Witold Rybezynski, One Good Turn: A Natural History of the Screwdriver (New York: Scribner, 2000).
7. Joseph Moxon, Mechanick Exercises, reprint of 1703 edition (South Dartmouth, Mass.: Early American Industries Association, 1975).
8. Charles Plumier, L’Art de Tourner, 2nd ed., reprint of 1749 edition (France: Librairie des Arts et Metiers-Editions, 1976).
9. Fred Holder, Making Screw Threads in Wood (East Sussex, U.K.: Guild of Master Craftsman Publications, 2001).
10. Charles Holtzapffel, Construction, Action and Application of Cutting Tools, vol. II (South Dartmouth, Mass.: Early American Industries Association, 1982 reprint of 1875 ed.).
11. Jim Packham, “The Screw Box and Tap: Tool-Making Tools,” The Chronicle 40, no. 1 (1987): 9-12.
12. Jim Packham, “Threading Gins,” The Chronicle 54, no. 4 (2001): 160-163.
Jim Packham, of Toronto, has been an active member of the E.A.I.A. since 1983. This is his tenth article for
Copyright Early American Industries Association Jun 2003
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