Scope:

The ASTM E618 standard test is a technique for assessing machining performance of ferrous metals using an automatic screw/bar machine that compares the machining performance of a single grade or kind of metal to another. Machining performance (HPM) is a new way for increasing the efficiency and productivity of machining operations by combining high-speed and high-precision machining.

Test Procedure:

For ASTM E618, the standard test piece is machined from bars using a specified number of tools in a specified sequence like sawing, turning, milling, and grinding. During machining, the metal is cut to a desired final shape and size. Then, the standard design parts are produced in the machines to uniform levels of quality with respect to surface roughness and size variation. The machining performance of the test metal in ASTM E618 testing is measured by the maximum rate at which test pieces can be produced within specified surface roughness. 

Much of modern-day machining is carried out by computer numerical control (CNC), in which computers are used to control the movement and operation of the mills, lathes, and other cutting machines which in turn increases the overall efficiency. 

Specimen size:

In ASTM E618, machinability standard test specimens are machined out of 1 inch (25.4 mm) diameter bar. 

Data:

Machining performance is reported in inch-pound and is considered as standard.

ASTM E618 can yield commercially relevant ratings for both materials selections and machine shop cost estimates.

Conclusion : 

ASTM E618 testing method is a production-type testing which evaluates the machining performance of ferrous metals. The test does not define limits of acceptability for any grade or type of metal.