The art of finishing or polishing wood and metal is very old. Originally it was done by taking the dried skins of sharks and rubbing the material. Later sandpaper and emery cloth were invented. As nearly as can be ascertained, emery cloth and sandpaper came into use about two hundred and fifty years ago. The process of manufacturing was then very primitive, consisting of coating the backing with glue, covering it liberally with the desired abrasive, shaking off the superfluous material, and hanging the sheet up to dry. The steady march of progress, however, has brought about wonderful improvements in the manufacture of abrasive papers and cloths. At the present time emery cloth is made from Turkish emery of different grades. Turkish emery is a hard black and brown stone found in Turkey and brought to this country for use in machine shops. Its quality, for hardness and durability in mechanical work, has never been excelled in any stone yet found. The cloth made is of various grades of coarseness. The numbers representing the grades of emery run from 8 to 120, and the degree of smoothness of surface they leave may be compared to that left by files as follows:

8

and

10

represent

the

cut

of

a wood rasp

16

"

20

"

"

"

"

a coarse rough file

24

"

40

"

"

"

"

an ordinary rough file

36

"

40

"

"

"

"

a bastard file

46

"

60

"

"

"

"

a second-cut file

70

"

80

"

"

"

"

a smooth file

90

"

100

"

"

"

"

a superfine file

120

F and FF "

"

"

"

a dead-smooth file