LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
The formula can be condensed into an even simpler one by rounding 3.8195 to
the next nearest whole number, which in this instance would be the number 4.
Where, rpm
=
revolutions per minute (spindle speed)
cs
=
cutting speed (feet per minute)
D
=
diameter of the workpiece (in inches)
4
=
constant (derived from process of cancellation and rounded to
the whole number).
This method is a short cut for finding rpm. The results obtained from its
use are accurate enough for practical purposes.
When we consider all the
variable factors which enter into the choice of the best cutting speed,
formulas giving exact answers have no significance in practice.
For
example, if a 2-inch diameter workpiece is to be cut at the rate of 120 feet
per minute, the spindle speed is calculated as follows:
or, using the condensed formula:
51
Previous Page
