Page:Popular Science Monthly Volume 91.djvu/264

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Applying the Idea of the Needle Bath in Shell-Making

THE steel utilized in the manufacture of explosive shells must be carefully tempered. If the steel is too brittle or too ductile the destructiveness of the pro- jectile is affected. Steel of the correct temper, however, does not lend itself readily to heavy machine opera- tions. For this reason, steel shells, after the in- sides have been removed from the blanks and most of the surplus material cut from the outside, are subjected to what is called "heat treatment."

The first step in heat treatment is to bring the shells to a comparatively WATE r high temperature. Then they are quenched, usu- ally in oil, and once more heated to bring the ma- terial to the proper condition.

Although projectiles of . all artillery ammunition must be heat treated, the cleverness of the French and the ingenuity of the Yankee has given manu- facturers a substitute for the oil bath which is an interesting and unusual adaptation of the familiar bath spray.

The accompanying illustration could with very little imagination be taken as a model of the original needle bath.

The shell bath is a cylindrical, double- walled receptacle, not unlike one ashcan placed within another. The space between the concentric walls forms a reservoir for a supply of water under pressure. The inner wall is perforated, and there is also a central perforated pipe passing through the top of the needle-bath, where it connects with a piece of ordinary rubber hose.

The shell to be cooled is placed in the main chamber, the perforated pipe in- serted in the nose of the shell and the water sprayed on the inside and outside of the heated case.

The shell is taken for this bath from a heating furnace where it has been kept at a temperature of 1800 degrees Fahren-

��Popular Science Monthly


���heit for some thirty minutes, and it remains in the bath until cooled thoroughly.

Plunging the hot shell immediately into a tank of cold water after taking it from the furnace would be treatment too heroic and would without doubt do a great deal more harm than good ; but the gentle cool- ing effect of the shower bath has proved highly efficacious. rubber hose a spray of cold water seems to be as beneficial to the temper of a shell as it is conceded to be to the temper of many a fractious youngster. — Reginald Trautschold, M. E.

��The shell is placed in the main cham- ber, the perforated pipe is inserted in the nose of the shell and the water is sprayed from inside and outside

��A Fortune from Old Razor Blades

A CALIFORNIA man is making a little fortune out of old safety- razor blades. It seems almost unbelievable but it is not more strange than the stories we hear of fortunes made by rag- pickers and dealers in old tin cans. This man pat- ented a suitable blade- holder, which he sells with supplies of old blades to tailors, mil- liners, show-card writers, and photographers. The holder is made from one piece of steel bent in half with its two sides pressing close together. One corner of the blade sticks out from the holder. It will cut one hundred ordinary sheets of paper or a dozen pieces of cloth at a single stroke.

���By means of a safety holder, the blades can be used for cutting cloth, paper or cardboard

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