634 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Chrome Vanadium steel, "Type D," made by the Halcombe Steel Co. 

 of Syracuse, N. Y. This latter steel may show a tensile strength as 

 high as 300,000 lb. per sq. in. Before the stretching process, the 

 cylinder should be hardened by heating to from 870° to 1000°, and 

 quenching in oil. The temper should not be drawn at all after this 

 hardening. It is not possible to get either of these two steels glass 

 hard like tool steel, unless by case hardening, so that it is possible to 

 enlarge a hole by reaming in a piece of steel so hardened, or even to 

 drill it. 



The dimensions of the cylinders are capable of some variation. 

 It has been my experience that the outside diameter of the cylinder 

 should be from six to ten times that of the inside hole. Not much is 

 gained by making it heavier than ten times, and it is likely to break if 

 made much less than six times. Several cylinders of four times the 

 diameter have eventually broken at 12000 kgm. although they with- 

 stood a seasoning pressure of 25000 kgm. Choice of dimensions must 

 furthermore be influenced by the consideration that there is a distinct 

 advantage in keeping the absolute dimensions of the apparatus small, 

 because hardening by cjuenching cannot reach to the interior of a 

 large piece of steel. I have found it convenient to use a diameter of 

 about ^ of an inch for the piston, and an outside diameter for the 

 cylinder of from 4 to 4^ inches. If the chrome vanadium steel is 

 used, the hole may be made initially h inch in diameter, and the 

 stretch after seasoning to 25000 kgm. will be small enough so that the 

 hole may be reamed to a final size of 32 of an inch. If the Krupp 

 steel is used, a slightly greater allowance for stretch must be made, 

 but it will still be less than j^ of an inch on a diameter of ^ an inch. 



The actual details of the seasoning require little comment. Pres- 

 sure should be increased gradually, stopping after every increase long 

 enough for the viscous yield to entirely disappear. The length of 

 the steps by which the pressure is increased may be so chosen that the 

 maximum is reached in from ten to fifteen steps. Pressure should be 

 maintained at the maximum for several hours. One application of 

 the seasoning pressure is sufficient, unless the stretch should be so 

 great as to make a second stroke necessary to reach the maximum 

 pressure. The seasoning pressure should be as high as can be reached 

 without permanent deterioration of the steel. With the grades of 

 steel mentioned above, this pressure may be safely as high as 25000 to 

 30000 kgm. A mixture of | (by volume) glycerine and I water is 

 suitable for transmitting the pressure during the seasoning. The 

 necessary length of stroke may be reduced by filling those parts of the 



