On Thu, 16 Apr 2015 02:59:33 -0400, "Steve W."
wrote:

Ignoramus29328 wrote:
I have a magnetic drill, an old looking one.

The drill motor works, the magnet does not.

I investigated the magnet a little bit. Here's what I found:

1) The bridge rectifier that was there, blows the breaker on the
electrical surge suppressor outlet

2) I replaced the old rectifier with another one that I had

3) Still no action on the magnet

4) There is a mysterious to me multiple position switch and resistors
and the switch appears to have arcing damage

Usually 3 position. Off, Position and Bore. Some have 4 position
switches, those have an AC feed to demag the work as needed.

Arc damage is likely due to the rectifier failing and sending AC through
the switch.


5) The magnet works if 110 volts DC is applied to it , bypassing the
above switch.

Good, they are not cheap to rewind.


I admit that I have never seen one of those in action and I do not
understand what function does the switch perform. Does it only turn
the magnet on and off and perhaps provide different magnetic strength?

Most are OFF,
Position - lower power to magnet so you can set the machine up and it
stays in place.
Then a Bore position. You get the drill set up, then just prior to using
it switch the magnet to full power to lock it down solid. Once you have
the hole bored you switch back to the lower setting. Keeps you from
overheating the coils.

Many also pull the drill motors power from the AC pins on the rectifier.



Or does it provide a demagnetizing function somehow? (I would expect
it to be unlikely as AC does not go into the switch).

I could take the easy route, junk everything, and replace it with a
new rectifier, connected directly to thhe magnet, and a AC input
switch.

That would work BUT with that magnet on full power you won't be able to
adjust the position of the drill. Wouldn't be a big issue if you're
boring vertical down. Any other position you want the lower power.


My question is,

1) how functionality much would I be missing with such simple wiring?
2) Given that the DC current at 110 volts is about 1.2 amps, how
likely would I be to overheat the magnet? (about 130 watts)
3) Anything else that I am missing?

I need to use this drill badly for two projects.

thanks


Well for a temporary set-up you might connect the rectifier up then feed
it AC through a light dimmer. Then you could dial the power up to hold
the drill in position, and turn it on full with a direct switch (only
because I wouldn't trust the dimmer)Then once you get the project done
get some better controls.
AC isn't nearly as hard on a switch as DC - - -