Page:Popular Science Monthly Volume 91.djvu/783

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Popular Science Monthly

��An abrasive made by fastening sharp sand, graded according to degrees of fineness, to paper with an elastic adhesive. The paper may have a grain or the fibers may be distributed generally

��ness, from No. oo to No. 3, the latter being about equivalent to sandpaper No. 2. Steel wool has a number of uses. It is a substitute for sandpaper, especially on curved surfaces, and it is useful in rubbing down paint and shellac. Like sandpaper it should not be used until all the work with cutting tools is done. It can be manipu- lated until utterly worn out. Other steel abrasives are: steel emery and crushed steel, and highly tern pered steel. Steel emery is the harder of the two being nearly as hard as diamond. They are used in stone sawing, the grind- ing of glass, and in lithography.

Sandpaper Sandpaper is made of two spe- cial kinds of pa- per — cylinder and Fourdrinier paper. Cylinder paper has a grain; that is, the fibers lie in one direc- tion, so that the paper tears easily in that direction. Fourdrinier paper will not tear readily in a straight line, because the fibers are distributed to give strength in every direction. The glue used to fasten the "sand" on the paper must be very elastic,

���Garnet -paper is made from natural rock crushed and sifted on glue-coated paper

��and hence of a fine quality. It also serves to strengthen the paper. The "sand" of sandpaper is crushed flint or quartz rock, and each particle of it is hard and sharp. This sand is carefully sifted and graded, so that sandpaper can be made in various grades according to the coarseness of the sand. The standards of coarseness are Nos. 4-0, 3-0, 2-0, o, y 2 , 1, 1 1/2, 2, 23^, 3, 2> l A and 4. These grades are printed on the back of each sheet. The difference between fine and coarse may be seen in the illustrations.

Sandpaper has a

disadvantage.

With use, the

corners of the

grains of sand

soon wear

smooth, so that

it does not last

long. For this

reason , it has been

displaced by

garnet-paper in

many instances.

Garnet-Paper

Garnet is a natural rock, (garnet ore), which is largely quarried in the Adirondack Mountains in New York State. It is crushed, sifted and measured, like the sand of sandpaper. It may be mounted, (glued) on a paper backing, for hand use, but

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