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Help with the magnet in a magnetic drill

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

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

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?

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.

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

Reply to
Ignoramus29328
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I suspect the switch provides " full " power to clamp the drill to the work, and can also apply less current in the opposite direction to demagnetise and let you get the drill off the work.

Dan

Reply to
dcaster

I suspect it is a 2 stage magnet - low power to position the base and get set up, and high power to hold the base for drilling. This reduces the power dissipation of the magnet to prevent overheating it. Why have it claped on full power when you are not drilling - yet turning odd the magnet allows the setup to be compromized by bumping it etc. Just remember - ALWAYS use a safety chain as a backup.

Reply to
clare

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.

Good, they are not cheap to rewind.

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.

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.

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.

Reply to
Steve W.

On 4/16/2015 2:59 AM, Steve W. wrote: ...

...

DC is MUCH more likely to do arc damage. With AC, the current goes to zero 120 times a second and gives an arc the opportunity to extinguish. Not so with DC. Full wave rectified AC looks more like AC than DC, but the inductance of the magnet will smooth it out enough to take away its reaching zero.

Bottom line: if Iggy needs to replace the switch, it needs to be DC rated!

Bob

Reply to
Bob Engelhardt

AC isn't nearly as hard on a switch as DC - - -

Reply to
clare

Hence why many components (like servo controllers) say never switch the output of a power supply. Always switch the AC input.

Reply to
Bob La Londe

Do you mean magnetic chucks, or are they magnetizing entire tables these days?

Reply to
Ed Huntress

Steve, and others, thanks a lot. The magnet works now. I can always ask a couple more guys to help with any kind of positioning.

i
Reply to
Ignoramus28245

The switch is on the AC side.

i
Reply to
Ignoramus28245

You could also try a transformer and switch BEFORE the rectifier.

Reply to
Bob La Londe

for only 130 watts, a small variac would be ideal for this.

Reply to
rangerssuck

And a 600 watt dimmer would be cheaper, smaller, lighter, and simpler.

Reply to
clare

OK, I guess, though I'd rather trust a variac than a home depot dimmer. But as you said earlier, ALWAYS use safety chains. Having that puppy land on your foot would probably ruin your weekend.

Reply to
rangerssuck

hey guys, best way to bypass a magnet on a milwaukee 4203?

Reply to
tom.innovativemotorsports

What make and model of drill is this?

Reply to
Christopher Tidy

Good morning,

I've got a Unibor EQ35N mag base drill ( 240 volt) The drill part is workin g fine However the magnet does not clamp. I have replaced the rectifier but still doesn't clamp. Is there a way to fix this or do I have to replace th e magnet. ?? . . .It's got a on/off switch which activates the magnet and t hen a separate on/off switch to start the drilling machine. Please help !! Thanks

Reply to
roos

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