Monday, May 2, 2011
More Toothing Plane Info
One of the first mention of a toothing plane is in the classic tool reference book, "Ancient Carpenter" by Henry Mercer. On page 127 and figure 120 he illustrates a "toothing plane" with the purpose of "scratching the surface of a slab of veneer to help the glue to stick."
The use of the Tooth Plane is very well desceribed ca.1815-1816 by James Smith in the "Panorama of Science and Art": "With this kind of plane, however hard the stuff may be, or however cross and twisted its grain, the surfacwe may be made everywhere alike, and will not be rougher than if it had been rubbed with a new fish-skin. This roughness may be effectively removed with the Scraper."
Joseph Moxon (who does not mention a toothed iron) tells us in "Mechanics Exercises" (ca. 1703): "But if it be very hard Wood you are to Plane upon on Box, Ebony, Lignum Vitae, &c. It is set (the iron) to 80 Degrees, and sometimes quite upright. So that these hard Woods, are, indeed more properly said to be Scraped, than Planed."
James H. Moncton, writing in "The National Carpenter and Joiner" (1873) states, page 6: "Veneering is a very simple operation and every carpenter ought to be able to do such work when needed; the surface of the material, upon which the veneer is to be laid, should be well scratched with at tooth plane..."
The conclusion is, in general, that the toothing plane is used both for leveling the wood surface, both on the carcase and the veneer, as well as providing an improved glue surface. I have used toothing planes for over 40 years and there is always one close at hand when I am at the bench.
I have posted some pictures of toothing irons. The oldest is by James Cam and was made in 1780. Note how much of the tooth is ground away. Normally the iron has grooves which are at least 1-2 inches on the end. The teeth grooves are made exactly like a rasp is made. The iron blank is annealed so that it is soft. Then, using a punch chisel, the maker punches the grooves along the end of the iron. The spacing between the grooves is determined by the use of the iron. Coarse, medium or fine grooves each has a purpose. Since the punch chisel is held at an angle, the grooves are slanted like teeth on a saw, producing teeth which are slanted when viewed from the end. Once the grooves are formed the iron is tempered and the bevel is ground using a wet stone. Never use a dry grinding stone since the temper of the teeth will immediately be destroyed.
To sharpen the iron, never put the grooved side on the stone. It is a simple matter to refresh the bevel side using wet stones (water or oil). The bevel angle is not important, but should not be too shallow, or the teeth will have a tendency to break off.
Toothing planes have a large range of angles, with the blades set often between 80 degrees and 105 degrees. I also use the iron by itself in my hand to reach difficult areas. I also have toothing irons which have been ground to a rounded end for concave surfaces.
When you select a plane, look for the length of grooves that are left. Longer is better. Also, look at the condition of the bevel. Many irons are improperly sharpened.