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► The C12 comes with the compact Centrotec bit
holder, as shown, but also includes the
standard keyless chuck (top image of the three
attachments). The optional offset and right-
angle chucks (lower two images) are awe
inspiring, and are a "must have" accessory in
my opinion.
My Background: I am an electrical engineer, and my
current occupation is Sr. Technical Writer for an
international corporation. I use my engineering
background to write technical repair manuals for
sophisticated equipment, including such things as
lasers, robotic systems, and smartcard programmers,
to name a few.
In the past, I owned and operated a custom cabinet
shop, and am the true definition of a "tool junkie". I
also use to perform "tool tests" for several
woodworking magazines.
A year ago I was introduced to Festool products, and
was so impressed with them that I began rewriting
some of their owner's manuals in my spare time.
Supplement: How Variable Speed Controllers Work
A common misconception about variable speed
tools is that the speed is controlled with a variable
resistor, like the dimmer of a light switch. This
doesn’t work well for motors for two reasons.
First, is because energy is wasted pumping current
through the resistor. The second reason is that
whatever power that is not being used by the
motor has to be dissipated by the resistor. This
means that the battery would be providing full
power at all times, regardless how slow the motor
is turning. This would be like driving your car
with the gas pedal pressed all the way to the floor,
and trying to drive at the speed limit by constantly
pressing the brake pedal.
A more efficient way to control the speed of a
motor is to turn it on and off very rapidly. The
more the motor is turned on, versus turned off, the
faster it spins. Keep in mind that this switching is
happening so fast (several hundred times a
second) that the inertia of the motor keeps it
spinning smoothly.
This type of motor speed control is called Pulse
Width Modulation (PWM), and is also used in many
other applications to control power. Most recently,
even the old resistive light dimmers are being
replaced by solidstate PWM light dimmers,
because they are more efficient and do not pose a
fire hazard from overheating.
With a PWM motor control, the power pulses turn
on at a constant interval, but the duration of the
pulse is varied, as shown below. The longer the
pulses, the more current flowing through the
motor, and the faster it spins. When full power is
needed, the PWM circuitry is bypassed, and full
battery power is delivered to the motor.
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