Some Common Abrasives 



By Professor William Noyes 



Late Director of the Department of Wood- Working, Teachers' College, Columbia University, 

 and author of "Hand Work in Wood" 



WOOD may be either cut down with an 

 edged tool or worn down by abra- 

 sives. The common abrasives are 

 steel, a hard 

 mineral, or 

 a mineral- 

 like artifi- 

 cial sub- 

 stance. 



Steel is 

 used for 

 rubbing in 

 two main 

 forms : as a 

 file or rasp, 

 and in the 

 shape of 

 steel wool. 

 The teeth 

 of a file are 

 cut when 

 the metal is 

 soft and 

 cold. The 

 tool is then 

 highly tem- 

 pered, so 

 that the 

 metal be- 

 comes very hard and brit- 

 tle. At least three thou- 

 sand varieties of files are 

 made, each adapted to 

 its particular pur- 

 pose. They are 

 used chiefly for 

 scraping the sur- 

 face of metal, but 

 are also appli- 

 cable to wood for 

 certain purposes. 



Files are classi- 

 fied (i) accord- 

 ing to their out- 

 lines into taper 

 and blunt, (that 

 is, having a uniform 

 cross-section through 

 out) ; (2) according to the 

 shape of their cross-section, 

 into flat, square, three- 

 square or triangular, knife, 

 round or rat-tail, half-round, 



The coarse side of a carpenter's rasp magnified showing the inden- 

 tations cut with a triangular point of a hardened piece of steel 



Steel wool shaved from the 

 edges of thin steel disks 



766 



etc. ; (3) according to the manner of their ser- 

 rations, into single-cut or "float" (having 

 single, unbroken, parallel chisel cuts across 



the surface), 

 double -cut, 

 (having 

 two sets of 

 chisel cuts, 

 crossing 

 each other 

 obliquely), 

 open-cut, 

 (having 

 series of 

 parallel 

 cuts slightly 

 staggered), 

 and safe 

 edge or safe 

 side, having 

 one or more 

 uncut sur- 

 faces ; and 

 (4) accord- 

 ing to the 

 fineness of 

 the cut 

 (rough, 

 bastard, 

 second cut, smooth, and 

 dead smooth). The "mill 

 file," a very common 

 form, is a flat, ta- 

 pered, single cut file. 

 One of the two 

 sides of a car- 

 penter's rasp 

 is shown mag- 

 nified in the il- 

 lustration. 



The fine or flat 

 side is composed 

 of a series of edges, 

 made by cutting 

 lines, whereas the 

 rough , half round side 

 is made by cutting 

 indentations with a tri- 

 angular point. 

 Steel wool is shaved 

 from thin disks of steel hela 

 together in a lathe. There 



are various grades of coarse- 



