Plant For Forging Rifle Barrels

: The Working Of Steel

The forging of rifle barrels in large quantities and heat-treating

them to meet the specifications demanded by some of the foreign

governments led Wheelock, Lovejoy & Company to establish a complete

plant for this purpose in connection with their warehouse in Cambridge,

Mass. This plant, designed and constructed by their chief engineer,

K. A. Juthe, had many interesting features. Many features of this

plant can be modi
ied for other classes of work.

The stock, which came in bars of mill length, was cut off so as to

make a barrel with the proper allowances for trimming (Fig. 21).

They then pass to the forging or upsetting press in the adjoining

room. This press, which is shown in more detail in Fig. 22, handled

the barrels from all the heating furnaces shown. The men changed

work at frequent intervals, to avoid excessive fatigue.

Then the barrels were reheated in the continuous furnace, shown

in Fig. 23, and straightened before being tested.

The barrels were next tested for straightness. After the heat-treating,

the ends are ground, a spot ground on the enlarged end and each

barrel tested on a Brinell machine. The pressure used is 3,000 kg.,

or 6,614 lb., on a 10-millimeter ball, which is standard. Hardness

of 240 was desired.

The heat-treating of the rifle blanks covered four separate operations:

(1) Heating and soaking the steel above the critical temperature

and quenching in oil to harden the steel through to the center;

(2) reheating for drawing of temper for the purpose of meeting the

physical specifications; (3) reheating to meet the machine ability

test for production purposes; and (4) reheating to straighten the

blanks while hot.

A short explanation of the necessity for the many heats may be

interesting. For the first heat, the blanks were slowly brought

to the required heat, which is about 150 deg.F. above the critical

temperature. They are then soaked at a high heat for about 1 hr.

before quenching. The purpose of this treatment is to eliminate

any rolling or heat stresses that might be in the bars from mill

operations; also to insure a thorough even heat through a cross-section

of the steel. This heat also causes blanks with seams or slight

flaws to open up in quenching, making detection of defective blanks

very easy.

The quenching oil was kept at a constant temperature of 100 deg.F.,

to avoid subjecting the steel to shocks, thereby causing surface

cracks. The drawing of temper was the most critical operation and

was kept within a 10 deg. fluctuation. The degree of heat necessary

depends entirely on the analysis of the steel, there being a certain

variation in the different heats of steel as received from the mill.