Table 2: Lathe cutting Sppeeds for Staright Turning and Threading

Lathe Operations
Page Navigation
49

(a) The cutting speed of a cutter bit is defined as the number of feet

of workpiece surface, measured at the circumference, that pass the cutter

bit in 1 minute.

The cutting speed, expressed in feet per minute (fpm),

must not be confused with the spindle speed of the lathe which is expressed

in revolutions per minute (rpm). To obtain uniform cutting speed, the lathe

spindle must be revolved faster for workpieces of small diameter and slower

for workpieces of large diameters.

(b) The proper cutting speed for a given job depends upon the hardness

of the material being worked on, the material of the cutter bit, and the

feed and depth of cut to be used. Table 2 lists specific ranges of cutting

speeds for straight turning and for threading under normal conditions. It

is proper to start machining operations at these speeds and observe the

effect on the cutter bit

TABLE 2. LATHE CUTTING SPEEDS FOR

STRAIGHT TURNING AND THREADING.