Factors Affecting The Spark Stream.

Metal Properties, Characteristics, Uses, And Codes
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much like that of wrought iron.

(6) Tungsten.

This is the easiest metal of all to recognize

because of the dull red color it imparts to the spark stream,

especially near the grinding wheel.

(7) Cast Iron. Cast iron sparks are of medium length; the carrier

lines are dull red near the grinding wheel and they end in bright

curved spear points coming out of very fine carbon bursts.

(8) High-Speed Steel with Tungsten.

The spark streams are very

simple in appearance and are composed of a few long, dull-red,

carrier lines having no carbon bursts at all.

(9) High-Speed Steel with Molybdenum.

For this type steel, the

spark stream is shorter and denser than for high-speed steel with

tungsten.

The sparks are definitely orange or straw in color with

small amounts of red near the grinding wheel. The carrier lines end

in spear points preceded by at least occasional carbon bursts.

Factors Affecting the Spark Stream.

The streams emitted by

high-speed steels are affected considerably by a number of factors.

The following subparagraphs provide a listing of these factors.

(1) Grinding conditions and the condition of the steel itself.

(2) Whether the steel is annealed or hardened.

(3) Whether a small wheel on a portable grinder, as opposed to a

large wheel on a bench grinder, is used.

(4) Grinding pressure, specimen size, and the shape of the region

being ground.

(5) The best way to avoid pitfalls is to perform the spark test by

direct comparison with a standard of known composition. Only in this

manner can the maximum benefits of spark testing be obtained.