414 
MINUTES OF PEOCEEDINGS OF 
A steel ingot or block which stands all the foregoing tests is “ rough 
turned/' care having been taken to fix it truly central in the lathe by means 
of a chuck at the muzzle, and the small projection at the breech, round 
which the slice for testing was cut away. In this operation a lip or collar 
is formed at the muzzle, to facilitate the lifting of the tube in and out of 
the furnace and oil bath. The machine is a turning lathe on the ordinary 
principle. It admits of two cutters working simultaneous^, and is capable 
of doing rough or fine turning as required. The fine turning is not done 
until the B tube and breech coil are gauged and ready to be shrunk on. 
The block is next bored roughly from the solid, 8J inches of diameter 
being taken out by one cut in segmental chips |th of an inch thick. The 
boring head is the ordinary shaped “half-round bit" with one pointed 
cutter set angularly, and three steel burnishers. The average time for this 
rough boring is 56 hours. After this the chamber (which is in all Eraser 
guns), is roughly formed by means of a cylindro-conoidal head with one 
long cutter and six steel burnishers, two on the taper part and four 
on the cylindrical. Average time 12 hours. Rough and fine boring, 
forming the chamber, and broaching, are all effected in the same horizontal 
machine (the difference being in the shape of the boring head and cutters), 
in which the barrel revolves, while the boring head, guided by bearings at 
the muzzle, simply progresses down the bore, being fed to its work by a 
long screw which passes through a nut in the sliding saddle to which the 
bar is fixed. 
The tube thus formed is now ready for toughening in oil. This consists 
in heating the roughly bored tube (from 4 to 5 hours) to the approved 
temperature in a vertical furnace, and then plunging it bodily into an 
adjacent bath of rape oil, in which it is allowed to cool and soak till next 
day, generally 12 hours or more. 
The following graphic description of the operation is extracted from an 
excellent treatise on “ The Management of Steel/' by Mr. George Ede, of 
the Royal Gun Eactories :— 
“ The tube is lifted by a powerful crane, and placed in a perpendicular position 
in an upright furnace; an iron coil, about 6 inches in depth and about 1 inch longer 
in diameter than the diameter of the block of steel, is placed upon the fire bars at 
the bottom of the furnace for the block of steel to rest upon; beneath this iron 
coil is placed a piece of plate iron, to prevent the cold air as it passes through the 
bars coming in contact with the extreme end of the block of steel, and in order to 
obtain an uniform temperature at the extreme end of the block of steel, this iron coil 
is filled with wood ashes. The iron coil becomes filled with the wood ashes while 
heating the furnace to a red heat with refuse wood, previous to putting the steel in 
the furnace. Alter the block of steel is placed in the furnace, the bottom end of 
it is then surrounded with some short blocks of wood, the damper is not lifted 
until the extreme end has acquired a low red heat, after which the damper is lifted. 
most satisfactorily; but it is a fact that the denser the steel is— i.s. the more it is hammered in the 
process of drawing out—the less heat does it require for successful toughening; hence each indi¬ 
vidual barrel must be tested. Doubtless a little more experience will teach us the exact mildness 
■'•and density suitable for a steel barrel, and the proper temperature to which it should be raised, 
before being immersed in the oil. 
