9
4. To lower the saw head with power off, pull and turn
the red knob (manual override) on the electro-
magnetic valve (see figure 6).
Figure 6: Lowering head with power
off
Electro-
Magnetic
Valve
Red
Relief
Button
Controlling the Cut:
Hydraulic Feed Control
The weight of the saw arm provides all the force
needed to move the saw blade through the workpiece.
In fact, if the full weight of the arm is allowed to make
the cut, rapid blade wear and poor cutting accuracy
will result. A hydraulic feed control is provided that
gives the operator a means to control the speed and
efficiency of cutting.
The hydraulic cylinder is attached between the
saw base and the saw head. The hydraulic cylinder
resists movement of the saw head in the downward
direction. However, the hydraulic cylinder offers no
resistance when the saw head is raised upward.
The amount of downward force can be controlled
by using the feed rate control valve. When the valve is
opened slightly, the saw head will move downward.
The further the valve is opened, the faster the saw
head will move downward.
The feed control is adjusted by the operator until
the saw is operating efficiently. This is usually
determined by observing the chip formation. (See
Evaluating Blade Efficiency for more information on
cutting efficiency.)
Evaluating Cutting Efficiency
Is the blade cutting efficiently? The best way to
determine this is to observe the chips formed by the
cutting blade.
If the chip formation is powdery, then the feed rate
is much too light, or the blade is dull.
If the chips formed are curled, but colored — that
is, either blue or straw-colored from heat generated
during the cut — then the feed rate is too high.
If the chips are slightly curled and are not colored
by heat — the blade is sufficiently sharp and is
cutting at its most efficient rate.
Blade Selection
The cut-off saw is provided with a saw blade that is
adequate for a variety of cut-off jobs on a variety of
common materials. A 4/6 vari tooth bi-metal blade
(5674011) and a 6/10 vari tooth bi-metal blade
(5674021) are available from JET.
See
Setting Blade Speed
for the speeds recom-
mended for various materials. These selections, while
appropriate for many shop cutting needs, do not
encompass the wide variety of blades of special
configuration (tooth pitch and set) and special alloys
for cutting unusual or exotic materials.
A coarse blade could be used for a solid steel bar
but a finer tooth blade would be used on a thin-wall
tube. In general, the blade choice is determined by
the thickness of the material; the thinner the material,
the finer the tooth pitch.
A minimum of three teeth should be on the work
piece at all times for proper cutting. The blade and
workpiece can be damaged if the teeth are so far
apart that they straddle the workpiece.
For very high production on cutting of special
materials, or to cut hard-to-cut materials such as
stainless steel, tool steel, or titanium, you can ask
your industrial distributor for more specific blade
recommendations. Also, the supplier who provides
the workpiece material should be prepared to provide
you with very specific instructions regarding the best
blade (and coolant or cutting fluid, if needed) for the
material and shape supplied.
Blade Break-in Procedures
New blades are very sharp and, therefore, have a
tooth geometry which is easily damaged if a careful
break-in procedure is not followed. Consult the blade
manufacturer’s literature for break-in of specific blades
on specific materials. However, the following proce-
dure will be adequate for break-in of JET-supplied
blades on lower alloy ferrous materials.
1. Clamp a round section workpiece in the vise. The
workpiece should be 2 inches or larger in diam-
eter.
2. Set the saw on low speed. Start the cut with a
very light feed rate.
3. When the saw has completed 1/3 of the cut,
increase the feed rate slightly and allow the saw to
complete the cut.
4. Keep the same hydraulic cylinder setting and
begin a second cut on the same or similar
workpiece.
