On 2008-05-05, SteveB toquerville wrote:

I have two of the Singer sewing machine foot speed controls. Would these
work on a drill press? I guess one would just wire them directly to the
cord. Yes? No? Definitely? Maybe?


No! Even

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if you can read it (proportional space fonts probably will render it
difficult to read, fixed should be fine.

The motors on the Singer sewing machines (e.g. my 221
"Featherweight") are brush equipped universal motors, and will vary
speed with applied current and with load to some extent. These motors
will work with either DC or AC.

The foot speed controls are variable series resistance -- done
by a stack of carbon blocks which get squshed together by the foot
pressure to reduce their resistance and allow more current through to
the motor.

And since there are three pins on the connector from the
controller to the sewing machine, yet only two pins on the power cord
(long before the common grounded outlets), I strongly suspect that the
foot speed controller is varying the current only to one of two places
which get power in a universal motor. Those two pieces are the rotor
(through the brushes and commutator) and the field (stationary magnetic
frame).

Hmm ... the power cord is on those three pins too, so it may be
just to get power to the light on the sewing machine. Skip the idea of
the split rotor and field windings.

Any reasonable sized drill press will have an induction motor --
no brushes, AC only, and their speed is mostly controlled by the power
line frequency (within a narrow range, unless the drill press is large
enough to have a three-phase motor which can be speed controlled by a
VFD.) Your sewing machine foot speed control will at most change the
torque load at which the motor stalls. And given the relaive size of
the sewing machine motor and the drill press motor, it will quite likely
burn up the foot speed controller fairly soon.

Now -- an exception to this is my little Cameron Precision
sensitive drill press, with a fairly small universal motor. This would
probably work with the foot speed control. But -- it works fine on a
little speed control box designed for the Dremel tools from before they
came with speed controllers built in. :-) This keeps me from being
tempted to render my sewing machine useless.

I bought them, along with two
barbecue spit motors to someday make a welding positioner.

Do the spit motors have brushes? I thought that they were
AC-only motors, so I don't think that the sewing machine speed
controllers would work with them either.

Although my
latest idea is to make a gas tank tumbler to clean out my welder gas tank
with some sand and metal nuts and washers.

Again -- make sure that the spit motors are brush type if you
want to control the speed.

Good Luck,
DoN.

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