Setting the Spindle Rotational Speed
Once you have determined the proper speed and feed rate for the material that
you are cutting and the type of cutter that you will be using, you will need to
setup your machine to cut within the range of the selected speeds and feed
rates.
Setting the spindle speed is a two-stage operation consisting of an initial belt
position setting and a final adjustment with the variable speed selector on the
front of the gearbox.
The drive system on your machine is much like a car with a manual
transmission. It has a “transmission” with several gear ranges and a “throttle”
to vary the speeds within each gear selection.
The belt positions give you three speed ranges and the electronic control gives
fine adjustments within the selected range. The variable speed selector dial
shows the speeds for each of the three speed ranges. These speeds are
applicable to both the lathe and mill spindles.
Step 1:
Refer to a machining reference guide such as the Home Machinist
Handbook or Ready reference to determine the optimal rotational spindle speed
for the materials and tooling you are using.
Step 2:
Examine the decal that surrounds the variable speed selector dial to
determine which of the three belt positions need to be selected inside of the
gearbox. The low-speed range located on the inner ring of the dial (0-400 rpm)
will require using the low-speed idler pulley and a dual-belt setup. The mid and
high-speed ranges will use a single belt that bypasses the center idler pulley.
Figure 8.1 Use the Granite Speed Dial for fine adjustments
! NOTICE !
Many reference charts give feed and speed rates
for high speed steel cutters. Most work today is
done with carbide cutters which can cut at much
faster rates. If you are using carbide cutters,
make sure the charts you are referencing are for
carbide cutters.
Granite 1300 Series Operator’s Manual
8-2
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