26 —
M
achinist
c
alc™
P
ro
rPm (SPINDlE SPEED)
RPM
is the rotational speed of the spindle in revolutions per
minute. In a milling machine or drill, the Spindle Speed is the
rotation of the attached cutting tool. In a turning machine, it is
the rotation of the attached workpiece. RPM can be calculated
given values for Diameter and Cutting Speed.
RPM –
Milling
Calculate the Spindle Speed (RPM) when milling with a .375"
bit at a Cutting Speed of 300 sfm (surface feet per minute):
RPM
Diameter: .375
″
KeySTROKe
DISPLAy
O O
0.
1. Enter the bit Diameter:
. 3 7 5 d
DIA
$
0.
375
INCH
2. Enter the Cutting Speed:
3 0 0 C
CUT
$
300.
feeT/MIN
3. Calculate the Spindle Speed (RPM):
R
RPM 3056.
R
CUT
$
300.
feeT/MIN
R
DIA
$
0.
375
INCH
r R
*
RPM
$
3055.7749
* The calculated RPM is displayed as a rounded, whole number value.
r R
displays the stored RPM value in decimal floating point format.