According to a study conducted by the Institute for the Science of Labor in 1943，a professional carpenter uses 179 different tools on average. Among them are 49 types of chisels belonging to 12 separate categories. This constitutes the standard set of chisels used in modern carpentry. What types of chisels were used from the 17th to 19th centuries? My research into various reference materials concerning architectural chisels has yielded the following findings. (1) Architectural chisels can be classified into three categories; (a) those for treating conjoined parts; (b) those for boring holes for connecting devices such as wooden pegs and nails; and (c) those for boring curved holes. At least about 50 chisels， in 14 different varieties， have been used by trained professional carpenters in the 17th-–19th century. (2) Architectural chisels that share a standard shape have been given different names acoording to blade width. (3) The average length for standard –shape architectural chisels can be estimated at about 1 “shaku” ， of about 300 millimeters. (4) The handles of architectural chisels are made of oak， ebony， rosewood and hinoki， or Japanese cypress. (5) The blades of architectural chisel have a standard width. The difference between the narrowest and widest blades was about 1 millimeter. I could not confirm a similar standard for neck length. (6) Architectural chisels are made by inserting the tang into the handle， and then reinforcing the connection with the ferrule. (7) Changes in working postures resulting in improved work efficiency seem to have occurred sometime from the late 18th to early 19th century. (8) Among the 29 architectural chisels used by a single carpenter in the early 19th century， seven different signatures inscribed by blacksmiths have been identified.

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The word “kobiki” refers to traditional hand —sawing experts. At present， only about 10 kobiki remain in Japan. Recently， we visited the lumbermill of Mr. Iichi Hayashi， a senior kobiki working in Tokyo 's Kiba area， for an on —site study. Mr. Hayashi uses a wide rip saw called a “maebikioga.” He takes repeated breaks from his work to resharpen the teeth of his saw with a file. Setting of the saw is an important part of a kobiki's work which consumes as much time as the process of sawing itself. In the old days， a style called “tategaeshi” was used， in which logs were set obliquely， but nowadays “sukuibiki” – in which logs are sawed as they lie flat on the ground —— is more popular. Sawing by kobiki is much more time–consuming and costly than that by machines， but demand for their services remains strong. Kobiki can work on logs in sizes beyond machines' operational limits; can bring out the beauty of the wood's grain better; and can reduce waste by sawing logs into custom shapes. However， their continued existence is now in danger: the remaming kobiki have been having a hard time finding successors， while the blacksmiths who manufacture wide rip saws and sharpening files are disappearing.

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Until the beginning of the Meiji Era (1868 –1912)， Japanese smoothing planes had long employed a single cutting iron. Under the influence of Western planes with their double irons， however， a double cutting irons became standard. Double cutting irons are designed to prevent torn grain. To a craftsman， however， the smoothness and gloss of the finished surface are the major considerations. Using Sugi (Japanese cryptomeria)， Hinoki (Japanese cypress) and Yellow ceder， we conducted finishing work with a smoothing plane using irons angled at about 40°. We changed the mouth openning distance fron 0.1 to 0.4mm，and measured and compared the surface smoothness of wood treated with single and double cutting irons. Even with a single cutting iron， at cutting depths of about 50μm， no torn grain appeared. As the mouth opening became wider， the single cutting iron produced increasingly rougher surfaces. Using the double cutting iron with narrower mouth openings， which allow back iron to be utilized， the surface was rougher than that profuced by a single cutting iron with a narrow mouth opening. In a comparison of the single cutting iron with a narrow mouth opening and the double cutting iron with a wide mouth opening， no differences in surface roughness were seen. In terms of type of wood treated， Sugi(Japanese Cryptomeria) yielded a fuzzier and rougher surface than either Yellow ceder or Hinoki (Japanese cypress).

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