The Plumb Bob
This article takes its inspiration from several phone conversations with Bruce Cynar of Fort Wayne, Indiana and from his publication The Plumb Line. Bruce is General Manager of News Channel 15 in Fort Wayne and an avid plumb bob collector. So I want to thank Bruce for sharing his knowledge and providing the photos for this article.
Egyptians certainly used plumb devices to build the pyramids, and perhaps others used them earlier. These very early bobs were simply shaped stones, sometimes with grooves around them to keep the line from slipping off. Such crude bobs, with no thought yet of a point at the bottom, offered sufficient accuracy for their purpose. An early improvement was the drilling of a hole to attach the line. Illustrations of early plumb bobs appear in the December 1992 issue of The Plumb Line.
The plumb bob evolved to meet requirements for accuracy in such functions as erecting tall buildings, installing machinery, mining and surveying. Symmetrical construction to assure the plumb bob would hang on its central axis, affixing the line on the central axis with the point, and the point itself were the improvements that brought us to the bobs we find in American hardware catalogs of the 1800s (Shannon, Walter's, Russell & Erwin, Hammacher Schlemmer etc.). Most bobs offered in this general market were heart shaped, with an occasional turnip shape, and were made of brass, lead or iron. Steel points were offered with some bobs and japanning was offered with some iron bobs. Several catalogs had the same selection suggesting a common manufacturer.
But not all plumb bobs of this period were so mundane. Collectors have bobs of ivory, bone, pottery and wood. There are little bobs for clockmaking, large bobs for shipbuilding, bobs for special purposes, and bobs with exotic shapes and extraordinary hand-done decoration and filigree. Figure 1 shows Bruce with some of the bobs that occupy a wall in his home. Figure 2 shows a whale bone bob to the left of three ivory ones. Figure 3 shows three shapely brass bobs. Note the amount of decoration on all of these bobs. Many of the finest brass plumb bobs are from England.
Figure 1. Bruce Cynar and a few bobs.
Figure 2. Whale bone & ivory bobs.
Figure 3. Brass plumb bobs.
Stone masons of the guilds in Europe relied on plumbs and plumb levels in their work, and the importance of these and other tools has carried over symbolically into Freemasonry. In the current Williamsbwg exhibition, Tools: Working Wood in Eighteenth-Century America, there is a Master's Chair from a Virginia Masonic Lodge that dates to the late 1760s. As shown on page 45 of Jay Gaynor and Nancy Hagedorn's exhibition book (same name), it's decorated with symbolic tools including three plumb bobs which symbolize uprightness. Masonic Trestle Boards of the 18th century depicted both the plumb board and the plumb level. And, the plumb bob is the symbol of a past master. I've wondered whether the more exotic brass or ivory plumb bobs that collectors prize may not have had their origins in Freemasonry, either as symbols of office or as gifts for service; but, an expert in Freemasonry assures me this is not the case, at least in England or America.
"What should we do with the string?" is a question answered in three issues of The Plumb Line. There are three options with multitudes of variations: (1) store the line on a device off the plumb bob, (2) store the line on the outside of the bob and (3) store the line on a reel inside the bob. This third option includes some of the most complex mechanisms among all hand tools. Let's examine the three options.
(I) Off-bob line storage: Spools or bobbins are commonly used to store line; some have handle-spindles to facilitate winding and unwinding. There are homemade and manufactured examples and finely-crafted examples in exotic woods, brass or ivory. An occasional spool is hollowed out at one end so the bob can be stored in it for protection. There is even a simple, but patented, bent-wire device for storing line. There are also spring-loaded reels, including a patented square reel case with a nail mounted within its top so the case can be nailed in a position for the bob to be hung from it. For tall-building construction or mining, where long lines were necessary, large reels resembling fishing reels were used. If bobs were very large, wire may have been used in place of line.
(2) On-bob storage: Some plumb bobs are constructed to provide space on the bob to store the line. Laroy Starrett patented the first slender cylindrical plumb bob in 1906. It has a space of reduced diameter at the top for winding the line. Incidentally, this may have been the first plumb bob to be mercury-filled to increase its weight. Mercury weighs about 75% more than steel. Traditionally-shaped plumb bobs may have a flange or wide brim on the cap so that the line can be wound on the space between it and the body of the bob.
A variation of this is to have a free-spinning spool between the cap and the body of the bob. Knurled edges on the spool assist in hand winding the line. In either of these variations the line usually passes upward over a notch or grooves on the flange or brim of the storage space, across a slot in the cap and up through the center of the cap such that the line is frictionally engaged.
One on-bob device stands out. It was patented June 2, 1874 by Justus Traut of New Britain and assigned to The Stanley Rule and Level Company. It is called the "adjustable" plumb bob and appears in my 1879 and 1909 Stanley catalogs. Stanley aficionados will know how long after 1909 it was offered. Examples may have the application date of April 28, 1874 stamped on them rather than the patent issue date. On top of the bob proper is a frame that holds a reel with knurled edges for hand winding. The line passes from the reel upward through the center of the cap. Between the reel and the frame on one side is a spring of appropriate tension so that the reel will hold unused line under the weight of the bob alone. A slight jerking of the deployed line causes more line to be released. I don't know whether the name "adjustable" comes from this feature or from the fact that tension in the spring can be varied slightly. An improvement to this kind of bob was patented in 1897 by Albert Kilbourne of West Pike, Pennsylvania. He added a coil spring inside the reel and a brake to hold the line.
(3) Internal Storage: There are three kinds of internal storage reels: reels with external cranks for winding the line, reels that are wound by turning the stem or body of the plumb bob and spring-loaded reels that rewind automatically. Most have either a brake on the reel or a friction device in the cap to keep line from unwinding when the bob is in use. Bruce believes the development of internal reels satisfied a "quest for gadgetry" and was strictly American. Let's look at three different internal reels, one from a New Jersey inventor.
The first American patent for a plumb bob was granted to Benjamin Chappell of Norwich, Connecticut on November 13, 1860. On April 3, 1962, over 100 years later, Lional Knaus of Worthington, Ohio patented a plumb bob whose internal mechanism is almost identical to Chappell's; but, it did have a different approach to clamping the line. The Knaus bob is shown in Figure 4.
Figure 4. Knaus bob with mechanism similar to Chappell's.
You'll see a top section with a reel and an enclosed coil spring. This top section screws into the hollowed-out bottom section, which is the way most internal-reel bobs were constructed. To the left of the spring case is a large gear that meshes with a small gear on a shaft above the case. The shaft also has a large gear attached to it that meshes with a small gear attached to the reel. Thus, one turn of the spring case causes many turns of the reel. This feature permits a longer line to be employed than if there were a direct drive between the case and the reel. A friction brake compresses the line as it passes up through the top of the bob. Pressing the spring-backed screw shown in Figure 4 releases the line, which can then be pulled out or automatically rewound. The Chappell plumb bob line was clamped by screwing down the bob's cap.
On November 2, 1920 Eugene Stanley Bush of Pendleton, Oregon received a patent for a dual-spring, internal-reel plumb bob that became known as the "Lightning" plumb bob. This bob is shown in Figure 5. It has a two-part body with the mechanism attached to the top section. Bruce tells me that some of these bobs are so well made that it may not be obvious that they come apart. The reel is mounted in the center on a shaft with small pinion gears on each side that mesh with teeth on the outside of the two spring cases. The ratio of revolutions of the reel to the spring cases is 6.6 to 1. The brake consists of a pair of angle plates in the neck of the bob that close against the line when the cap is screwed down and release the line when the cap is loosened.
Figure 5. Bush dual-spring, internal-reel Lightning bob.
One of two New Jersey plumb bob patents belonged to Jeuleos Gambllee of Tenafly and was dated October 21, 1913. (The other patent belonged to Maschil Converse of Newark and was for a hollow plumb bob body spun or stamped from sheet brass.) Gambllee's plumb bob has a two-part body with an internal reel attached to the bottom section. There is a small pinion gear mounted on one side of the reel shaft that is engaged from above by a horizontal, circular crown gear. The crown gear is attached to a shank that extends above the neck of the bob and ends with a round, knurled finger piece that is fastened to the shank with a set screw. The top of the shank is threaded so that a nut on it (below the finger piece) can be tightened against the neck to prevent rotation of the shank. The line extends up through the shank and can be deployed by loosening the nut. The line is rewound by turning the finger piece with the nut loose. Since the crown gear has many more teeth than the pinion gear, a few turns of the finger piece will wind the entire line.
Figure 6 is not the Gambllee bob, but you'll see it has a similar, but simpler, mechanism.
Figure 6. Bob with mechanism similar to Gambllee bob.
All of the internal-reel bobs described have vertical reels. Some bobs have horizontal reels that operate in essentially the same way after the direction of the line is altered from vertical to horizontal.
This article does not cover manufacturers. However, the June 1992 issue of The Plumb Line lists over 150 manufacturers and dealers. While many are well known, others are not and we're not sure into which category they fall. One prominent New Jersey manufacturer and distributor, Kueffel & Esser Company, was founded in Hoboken in 1867. They became one of the largest manufacturers of surveyors' equipment including plumb bobs. Their 1927 catalog had 548 pages and included 5 plumb bobs in 11 variations.
If you want to know more about plumb bobs, the complete set of 16 issues of The Plumb Line is available from Bruce Cynar for $45. (Note: the September issue is the final issue.) Included are patent drawings for most plumb bobs, a list of manufactures and distributors, a list of collectors and dealers interested in plumb bobs, and many articles and pictures. If you want to see more pictures of some nice plumb bobs I suggest the color covers of David Stanley's catalogs of the last 5 years. Also, for a spectacular color display of plumb bobs see the centerfold of the Murland-Parker International Tool Auction of July 29, 1994.
Sometime next year we'll have a shorter article to wrap up this topic, to include information on plumb bob points and some unusual, special-purpose bobs. Thanks again to Bruce Cynar!
Part 1 appeared in the November 1994 Tool Shed and covered some history of the plumb bob and also the many ways that a bob's string was stored, including descriptions of several very complex internal line reels.
What about plumb bob points? Many bobs have points that are integral to the body of the bob. Certainly most bobs of the 1800s were made this way. Iron or steel points cast into the body probably came next. And then came the removable, reversible, and double points. These kinds of points were usually threaded and would screw into the bottom of the bob. The simplest one could be unscrewed, thrown away, and replaced by a new point if the old point was worn from being scratched on hard surfaces such as concrete or stone. Another kind of point could be removed and reversed, with the point screwed into the bob to protect it when not in use. The double-ended point could be reversed and the point at either end used. Some of these had different size ends for different uses; others had two identical points for use if one were worn or damaged. In modern days surveyors had plumb bob kits which included points of different sizes and of different materials. One had points of brass, lead, and copper, but none of iron as this would have affected the surveyor's compass.
If you run into a surveyor today, he might not even know what a plumb bob is. Today's surveyor shoots a tiny beam oflight from a laser to mark a point that would have been fixed by a plumb bob in days gone by. I stopped recently to chat with a young surveyor who was working on one of our local streets and this was my experience. There are a few unusual point designs that I'll now describe:
(1) The Willis Vajen plumb bob, patented November 14, 1882, is a pear-shaped bob with a cap and point that could screw interchangeably into either the top or bottom of the bob. See Figure 7. With the heavy end down it was claimed that the point would settle or become still much sooner. It was also claimed that marking the point by dropping the bob would be more precise with the heavy end down. On the other hand, it was claimed that the point is easier to see with the heavy end up. Vajen's point could be reversed and screwed into the bob to protect it.
Figure 7. The Vajen bob.
(2) Adam Leidgen patented, on March 3, 1885, a point that passed almost to the top of the bob through a central bore. The point could then be extended or retracted by means of a tubular clamp at the bottom of the bob. Its claimed advantage over other bobs was that when the bob is hanging the mechanic can make small adjustments in the length of the exposed point at the bob rather than returning to the place where the line is hanging and changing the string.
(3) On November 12, 1907 Orlando McQuaid of Franklin, Pennsylvania, patented a flat-bottom plumb bob with three short points to serve as legs. See Figure 8. As the three leg points define a plane, the bob will always settle when lowered to a surface from above. The point, being shorter than the legs, will come close to the surface after the bob has settled. The point is marked on the surface by hitting the top of the stem with a hammer. Another feature of this bob is that its stem passes through a central bore and up through the top of the bob. The bob point has a larger diameter than the stem and is threaded onto the bottom of the stem, thus the body is held on the stem by gravity. With this construction the body can be separated from the stem by unscrewing the point, and thus the stem can be passed through small holes in a floor as might be needed in multi-story buildings. Once the stem is through the hole, the body can be reattached and the plumbing continued through lower floors.
Figure 8. The McQuaid bob.
(4) One patented plumb bob and chalk holder has a small removable point that is mercury filled to increase the weight of the bob. (Mercury is about 75% heavier than steel.) Presumably this was done because the chalk-filled body is not as heavy as a solid bob. This may be one of the most worthless patent ideas in history!
(5) One other patented plumb bob has a point made of glass with a piece of phosphorus in it. It's claimed that this is useful in reflecting light in dark places.
Finally, let's look at two special-purpose plumb bobs:
1. John Lawlor of Scranton, Pennsylvania, patented a plumb bob for gas fittings on November 24, 1885. Its purpose was to aid plumbers or gas-fitters to install a drop from a gas line above a ceiling in a perfectly vertical position before a gas-burning lamp was attached to it. The device consisted of a frame with a few female collars for threading the frame onto drop pipes of differing sizes. A common plumb bob was suspended in the frame directly under the center of the drop pipe. There was an upward-facing point at the bottom of the frame, so that if the drop pipe were perfectly aligned the bob point would be directly over this point. See Figure 9.
Figure 9. The Lawler bob for gas fittings.
2. The plummet lamp is a plumb device adapted for a special purpose. They were devices that provided a visible reference point in underground surveying, especially in mining. In mining they would be hung from the roof of a tunnel. Early ones used burning fluid to create the light source; some from the 20th century were battery powered. Many of you have probably seen one at a major auction where they appear infrequently, and go for very substantial prices. Several were on dispiay at an Albuquerque tool meeting that I attended. One example, made by K & E, is shown in Figure 10. It appeared in a David Stanley catalog, and we thank David for permission to reprint it. To learn more about plummet lamps see the article by Dale Beeks in the Chronicle Volume 45 No. 2, page 41.
Figure 10. The Plummet bob.
John Roach of San Francisco patented his plummet Lamp on October 20, 1883. See Figure 11. The body of the bob provided a chamber to hold the burning fluid, or oil, and it was topped with a flange which was threaded on the inside and outside. A cap with a wick was screwed into the inner threads. A Chimney with glass windows was screwed onto the outside threads to provide a steady, clear flame. Air holes were provided in the chimney to aid combustion, and the line for hanging came through a perforation in the top of the chimney.
Figure 11. The Roach bob.
The ultimate reference on plumb bobs remains Bruce Cynar's The Plumb Line which was published in the early 1990s. Included were patent drawings for most plumb bobs; lists of manufacturers, distributors, dealers, and collectors; and many articles and pictures.