Hitachi FDV 16VB2 Technical Data And Service Manual page 11

(2) Speed control switch
The switch allows adjustment of the motor rotation within a range of about 10 % to 80 % of the full rotation
speed by changing the trigger stroke. The trigger stroke can be set to a desired position by means of the
stopper and micro-adjust knob.
The SCR incorporated in the switch for phase control of the power supply causes heat release to rise with
increasing current.
When the switch is used at S
gradually raise the heat release from the SCR eventually to a level high enough to break the SCR. To avoid
this, release the switch immediately, whenever the motor becomes jammed.
Speed
control dial
Low speed
(3) Impact to rotation changeover
The impact drill can be switched from IMPACT (impact
plus rotation) to ROTATION (rotation only) by rotating the
change lever. When boring concrete, stone, tile or similar
materials, sliding the change lever to IMPACT side. The
drill head impacts against the material while continuing to
rotate.
When boring metal, wood or plastic or tightening, sliding
the change lever to ROTATION side, the drill rotates as
an ordinary electric drill.
Instruct the customers to wait until the motor stops
completely without fail before sliding the change lever.
(4) Be sure to push the pushing button to "R" for grinding
operations, for instance with the drill chuck holding the
sanding set or the mounted wheel.
--- S in the figure below, keeping the switch energized with the motor locked will
0 1
Stopper
High
speed
Change lever
ROTATION + IMPACT
--- 8 ---
Trigger stroke
ROTATION