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  Sand Blast File Sharpening - American Machinist, October 18, 1879  

Note from the Editor: About a year ago I published a short article found in July 28, 1878 issue of "Engineering", a London-based Illustrated Weekly Journal. The article briefly described "that by subjecting worn files to the action of the jet, the cutting edges are rapidly renewed, and the file is made sharper than when new." The article below describes the same process in real-life application by American firm. WK

Sand Blast File Sharpening

The sand blast process of cutting raised figures on glass, marble, and other hard, brittle materials has been used for several years, but its use for sharpening files is a recent application.

The large engraving on this page will give a general idea of its operation. To the steam pipe (as near the boiler as convenient) is attached a finch pipe with elbow; to this is attached a piece of pipe of suitable length, inclined about 16 degrees from a horizontal line, with valve, into which a brass steam jet is screwed.

Next, the iron nozzle is wrapped with paper to fit the cylinder, the steam cylinder slipped on to steam jet to shoulder, with sand tube perpendicular, and the set screws fastened. The gun is then ready for use.

The operator then suspends a hopper, or funnel, of suitable size, to contain the sharpening material, as near directly over the gun as convenient, and connects with the gun by a rubber tube. When done using he removes the tube and plugs the hopper.

A box is made about four feet long, one foot wide, and eight inches deep, open at end next to the gun, also underneath the outer end, for the escape of steam and for carrying sand to the reservoir. This is inclined same as the gun, and set so that the end of the nozzle shall be flush with end of box, and opposite the middle of the aperture. The reservoir is placed under the end of this box from which the hopper is replenished as needed.

For a sharpening material moulder's parting sand is used. Flint sand or emery will wear longer, but any gritty substance may be used. The sand and water is kept in the hopper as thick as it will flow.

The file is first dipped in hot soda water and brushed with a card; should any metal remain in the grooves it is pecked out, as the blast does not remove it. The file is held so the blast strikes it at an angle of 16 degrees. It is passed under the blast from point to tang, giving it also a lateral motion so as to grind it evenly. The action of the blast is very rapid.

Two or more files can be placed side by side in cutting by the blast. Both old and new files are now being sharpened by the sand blast. The effect on new files is to remove the burr or curl from the teeth, thus changing every tooth into a sharp and regular chisel-shaped form.

This prevents the teeth breaking off and adds largely to the working value of the file. The burr is shown in Fig. A. In Fig. B the teeth are exhibited as left by sand blasting.

Many advantages are claimed for sharpening files by this process. The temper of the steel is not drawn; they cut faster and with less labor; leave the work very smooth; are superior for wood-work, as they cut like a plane, and do not tear the wood away; can be sharpened at small expense; secure the highest economy.

H. S. Manning & Co., Ill, - Liberty St., New York, have the agency for sharpening files by the sand blast.

American Machinist, October 18, 1879, (New York: American Machinist Publishing Co.)

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