15
6. Use a micrometer to measure the thickness
variation of the disk you have cut from the bar
stock. Measure at top and bottom of disk.
Figure 8-11
The saw blade can be considered correctly adjusted
when the variation measure is no more than 0.012
inch across the face of the disk.
If you do not have a piece of 2-inch bar stock
available for a test cut, use a larger diameter test
piece rather than a smaller one. The maximum
thickness variation on any test piece should be no
more than 0.003 inch, per side, per inch of stock
diameter.
8.11 Setting feed rate
Feed rate of blade into workpiece is important to
band saw performance. Excessive pressure of
blade against workpiece may cause stalling or blade
breakage. In contrast, insufficient pressure rapidly
dulls the blade.
The hydraulic cylinder resists bow movement in
downward direction. It offers no resistance when
bow is raised.
To increase feed rate, turn dial (U
1
, Figure 8-12)
counterclockwise. To decrease, turn clockwise.
To close hydraulic flow, turn lever (U
2
) down,
perpendicular to cylinder. To open hydraulic flow,
turn lever (U
2
) parallel to cylinder, as shown.
Feed rate is adjusted by operator until saw is
operating efficiently, usually determined by
observing chip formation. See section 9.3,
Evaluating cutting efficiency.
Figure 8-12: feed rate adjustment
8.12 Counterbalance spring
The counterbalance spring helps control amount of
weight, or feed pressure, the bow puts on workpiece
when hydraulic control valve is fully open. The
hydraulic cylinder will not compensate for improper
counterbalance. If spring is improperly set, one can
expect poor performance, crooked cuts, tooth
stripping, stalling, and/or blade running off wheels.
Spring tension has been set by the manufacturer,
and should not require adjustment. If future
problems arise, indicating improper counterbalance,
adjust spring as follows:
1. Disconnect machine from power source.
2. Open hydraulic cylinder valve and place bow in
horizontal position. Turn hydraulic cylinder dial
counterclockwise until it stops.
3. Place a weigh scale (such as spring or hanging
scale) beneath blade tension handle, and lift
saw bow. Scale should indicate approximately
5 to 6 kg (11-13 lb).
4. If adjustment is needed, loosen one nut and
tighten the other (Figure 8-13) on eye bolt, until
scale indicates 5 to 6 kg (11-13 lb).
A good indication of proper feed pressure is the
color and shape of the cutting chips. If the chips are
thin or powdered, increase feed pressure. If the
chips are burned and heavy, decrease feed
pressure. If they are still burned and heavy, reduce
blade speed. Optimum feed pressure has been set
when the chips are curled, silvery, and warm.
Figure 8-13: feed pressure adjustment
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