US2303258A - Reconditioning files - Google Patents

Description

Patented Nov. 24, 1942 RECONDITIONING FILES Simon M. Cleja and John W. Hladky, New York, N. Y., assignors to Trans-American Development Corporation, New York, N. Y., a corporation of New York I No Drawing. Application May 29, 1942, Serial No. 445,101

2 Claims. (Cl. iii-24) The invention relates to an improved process of chemically reconditioning used and worn steel files and like tools; the primary object of the invention being to reduce the time required to recondition the files and the like while substantially eliminating liability of the reconditionedfile's to either immediate and eventual deterioration or loss of durability growing out of the processing thereof.

Other important objects and advantages of the invention will be apparent from the following description wherein a preferred embodiment of the invention is set forth for illustration.

It is generally conceded that a satisfactory reconditioning of used and worn steel files can be achieved only through efficient performance of the following steps and operations:

(1) Cleaning, comprising (a) removal of organic and loosely adhering foreign matter, and (b) removal of iron oxide or rust and scale;

(2) Etching to resharpen the teeth or cutting edges; and

(3) Finishing, comprising (a) restoration of the original metallic gray color, (b) stabilization of the restored color, and (c) drying of the files .after treatment.

Although some of the prior art processes fulfill in one degree or another the above stated requirements, none of the prior processes of chemically reconditioning used and worn files are suitable for or capable of industrial applicationon a large scale whereby a large number of files can be satisfactorily resharpened in a working day.

The present invention overcomes the foregoing objection to present processes as Well as other to remove all loosely adhering foreign matter from them by immersing the files-in a boiling bath consisting of caustic soda solution prepared by dissolving from 50 to 100 grams of caustic Soda inl kilogram of water.

H. The files are then removed from the caustic soda solution and sprayed with water at a pres-- sure of about 200 pounds per square inch. The impact and washing action of the water at this pressure cleans the files thoroughly all over and removes all loose foreign matter not removed by the caustic soda bath. a

III. The files are placed in a bath consisting of about 165 grams of commercial hydrochloric acid (21 Be.) in ab'o'ut 1000 c.c. of Water, to remove the iron oxide which is not removed from the files by the caustic soda bath and the pressure washing. It is to be noted thatjfiles processed by steps I and II do not require long immersion in the hydrochloric acid solution, two or three hours being ample to remove the iron oxide and prepare the files for the next step.

IV. The files are washed all over with water sprayed at a pressure of about 200 pounds per important objections by making possible the following advances over the prior art:

(1) Resharpening of a large number of files in one working day.

(2) Obtain sharp and uniformly shaped teeth.

(3) The original durability of the files is unaffected.

(4) Very substantial reduction in the amount of time and labor required for the reconditioning.

(5) Elimination of the use of brushes or rinsing by substituting high pressure water spray for the usual brushing and rinsing operations prescribed by prior processes.

(6) Elimination of the necessity of greasing the reconditioned files through permanent restoration of the original gray metallic color of the files.

The steps and operations constituting the present invention are as follows:

I. The files to be reconditioned are degreased square inch. This removes all traces of hydrochloric acid and leaves a chemically clean metallic surface, ready for etching.

V. The files are immersed in an etching bath consisting of a 12% nitric acid solution, prepared by mixing 18 parts weight of commercial nitric- .a'cid (42 B.) and 82 parts by Weight of water.

The files are usually kept in this solution for from. five to six minutes, but the time can be extended. for a fraction of a minute longer, in the case of extremely worn files which require more etching than less worn files, although too long residence in the nitric acid bath is damaging to the file teeth. The temperature of the nitric acid bath during etching should not be permitted to go higher than 50 C. The files may or may not'be removed and reimmersed in the bath during the etching. It will be recognized that the nitric acid etching reduces the fiat tops of worn file teeth and restores their cutting edges.

VI. The etched files are sprayed all over with water at a pressure of about 200 pounds per square inch to wash them free of nitric acid and to arrest the etching action.

VII. The etching darkens the surface color of the files, and the natural metallic gray color of the files is restored by immersing the files for from ten to twenty minutes in a hydrochloric acid solution consisting of 340 grams of commercial hydrochloric acid (21 Be.) and 1000 c. c. of Water, in a ratio by weight of about 9 parts of acid to 1 part of water.

VIII. In order to prevent the rusting which normally follows quickly after the acid treatment, due to the catalytic efiect of traces of acid remaining on the surface of the files, the files are sprayed with water at 'a pressure of about 200 pounds per square inch to remove all such traces of acid.

IX. To rust-proof the files and fix the metallic gray color of the files, the files are immersed in a sodium silicate solution, preparedby mixing 1 part by volume of commercial sodium silicate (40 B.) with from 3 to 5 parts by'volume of water.

X. The files having been removed "fromthe sodium silicate are dried by suspending them freely in the air. The drying may be s'peededup by suspending the files in an air current produced by a blower or exhaust fan.

Although there is set forth and described herein a preferred embodiment of the invention, it lsnot desired to limit the application of the invention thereto, beyond the scope of the subjoined claims.

Having described the invention, what is claimed as new is:

1. In a time and cost reducing process of chemically resharpening used and worn files, said process involving immersion of the files in a hydrochloric acid bath for about 2 to 3 hours to remove and loosen foreign matter from the surface preparatory to etching with nitric acid, the step of spraying the files'with water at a pressure of about 200 pounds per square inch after removal from the hydrochloric acid bath, to remove remaining surface matter and traces of acid, then immersing the files in the nitric acid bath for a relatively short period of time, thereby restoring the sharpness of the file teeth, then washing the etched files and removing traces of nitric acid therefrom by spraying them with water at a pressure of about 200 pounds per square inch in orsquare inch to prevent immediate rusting of the files, then rust-proofing the files and stabilizing the natural gray metallic color thereof by immersing the washed files in a sodium silicate solution of about 1 part of sodium silicate in 3 to 5 parts of water, by volume, then removing the files therefrom and drying the files in the air.

2. In a quick-acting process of chemically resharpening files, consisting in first removing all foreign matter from the files by a short time immersion in a hot bath solution of from 50 to 100 grams of caustic soda in 1 kilogram of water; second removing the files from said bath and spraying them with water at a pressure of about 200 pounds per square inch; third placing the thus cleaned files in a second bath for 2 to 3 hours containing a solution of about 165 grams of commercial hydrochloric acid (21 B.) in about 1000 c. c. of water thus removing any possibly adhering iron oxide; fourth after removing the files from the bath subjecting them to a water spray of 200 pounds per square inch pressure in order to obtain a chemically clean metallic surface; fifth immersing the files during 5 to 7 minutes in an etching bath consisting of a 12% nitric acid solution containing a mixture of about 18 parts by weight of commercial nitric acid (42 B.) and '82 parts of water and at a maximum temperature of 50 0., thereby restoring the cutting edges of the files; sixth again spraying the files with water at a pressure of about 200 pounds per square inch in order to arrest the etching action; seventh immersing the thus cleaned files for 10 to 20 minutes in a solution consisting of about 340 grams of commercial hydrochloric acid (21 B.) and 1000 c. c. of water at a ratio by weight of 9 parts of said acid to 1 part of water, thereby restoring the natural gray color of the files; eight again spraying the files with water at a pressure of about 200 pounds per square inch in order 'to remove all traces of acid; ninth immersing the files in a solution of about 1 part by volume of commercial sodium silicate (40 B.) mixed with between 3 and 5 parts by volume of water,

in order to rust-proof the files and fix the gray color thereon; lastly removing the files from the bath and air-drying them preferably by free suspension in artificial draughtl SIMON M. CLEJA. JOHN W. I-lL'ADKY.