Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 144

Glasspaper is the chief abrading material used in woodworking, and consists of strong paper coated with powdered glass. In the manufacture of glasspaper, first the glass is washed and sorted, and then broken very fine by stamps or other machinery. The glass chiefly used for best glasspaper is that from old port wine and stout bottles; this, when pulverised, is of a golden colour. The different grades of glasspaper are numbered from 3 to 0 (and even finer), and there are corresponding sieves to divide the various grades, or to “size,” as it is technically called. These sieves are numbered from 140 to 30, the numbers representing the number of meshes per lineal inch; the finer sieves are covered with Swiss silk, the remainder with woven wire. In this part of the process considerable care must be exercised, as one large particle of glass on a sheet of fine paper would scratch the work upon which it was used, and would produce an uneven surface. The placing of the glass on paper requires considerable skill and experience. The workman has delivered to him plain paper in reams of 120 sheets, each sheet making four sheets of ordinary size. The appliances used are a copper holding 56 lb. of glue, a table, a bench on which the sheets are laid to cover them with glass, a hot plate for firing the sheets, a drying room, a cutting machine, and a press for packing and tying up. A ream or two of paper is placed on the table, and the top sheet is coated with glue by means of a brush resembling a boot-brush, but with longer hair. The sheet is lifted by two corners and laid on the bench, glue side uppermost; the bench has a border standing up some 7 in. or 8 in. high on three sides, with a narrow fillet in front. Powdered glass is simply thrown or scraped over the sheet, which then is raised from one side so that the superfluous glass runs off on to the bench and is used again. The sheet is then placed on the hot plate, a hollow, flat iron bench heated with steam; this causes the glue to boil up and thus securely fix the particles of glass on the paper. All this is done much more quickly than it can be described. After drying, the sheets are cut up and arranged in quires and reams ready for the market. Glasspaper has entirely replaced the old-fashioned sandpaper; this was made in the same way as glasspaper except that sharp, fine sand instead of glass was used.

Fig. 425.—Wrong Method of Forming Burr Edge.

Figs. 426 and 427.—Badly Sharpened Scrapers.

Fig. 428.—Special Steel Scraper.

Fig. 429.—Special Steel Scraper.