Grizzly Vertical Milling Machines G0728 - Manual (Page 29)

Model G0728–31 (Mfg. Since 11/11)
-27-
Adjusting Spindle
Speed
to select the correct spindle speed (rpM) for a
milling operation, you will need to: 1) Determine
the spindle speed needed for the workpiece,
and 2) configure the belts to provide the closest
calculated speed.
Calculating Spindle Speed
1. use the table in figure 31 to determine the
cutting speed or surface feet per minute
(sFM) required for the workpiece material.
Cutting Speeds for High Speed Steel (HSS)
Cutting Tools
Workpiece Material Cutting speed (sFM)
aluminum & alloys 300
Brass & Bronze 150
Copper 100
Cast iron, soft 80
Cast iron, hard 50
Mild steel 90
Cast steel 80
alloy steel, hard 40
tool steel 50
stainless steel 60
titanium 50
plastics 300-800
Wood 300-500
Note: For carbide cutting tools, double the cutting
speed. These values are a guideline only. Refer to
the MACHINERY'S HANDBOOK for more detailed
information.
figure 31. Cutting speed table for hss cutting
tools.
2. Measure the diameter of the cutting tool in
inches.
3. use the following formula to calculate the
required spindle speed rpM:
Cutting Speed (FPM) x 12
*
Recommended
Tool Dia. (in inches) x 3.14
=
Spindle
Speed
(RPM)
*
Double if using carbide cutting tool
Tools Needed Qty
Wrench 24 mm .................................................. 2
To set the spindle speed:
1. DisConnECt thE Mill FroM poWEr.
2. release motor pulley tension by loosening
the jam nut and then the tensioner bolt (see
figure 32).
Setting Spindle Speed
3. using the table in figure 33, arrange the
belts to provide the best rpM for the cutting
operation.
4. retension the belts to the proper tension (see
V-belt Tensioning on page 33).
figure 32. tensioner bolt and jam nut location.
tensioner Bolt
A
B I
II
III D
C
I
II
III
A
670
G0730/31
G0728/29
320
570
230
1650 1200
1420 2520 2170
B D
SPINDLE RPM CHART
PULLEY ARRANGEMENT
C
950 420
490
270
1720 1110
1410 3200 2050
figure 33. vertical milling machine rpM table.
Jam
nut