Drill press switch question

[m32825]

I've got a Delta drill press. I've had to replace the on/off switch about every 10 years. This is a 120V machine. Last time I replaced it I noticed that two conductors are being switched. Why is that? If I had a light bulb I would switch the hot to turn it on and off. What's different about a drill press? Thanks!

-- Carl

 

[American Locomotive]

Nothing really. Switching both poles is just common in power equipment, especially if the switch is used on 240v equipment.

 

[exmaxima1]

Nothing really. Switching both poles is just common in power equipment, especially if the switch is used on 240v equipment.

Exactly. But you can also wire the poles in parallel for 120v use and double the current capacity. Makes the switch last much longer.

 

[matt_i]

This is a really good application for a 120vac-coil ice-cube relay of around 15A capacity, sometimes they give one value for resistive loads and another for inductive/motor loads.

But, I would think the relay to last longer than 10yrs plus if it does go bad, simply unplug and plug in a new one with no tools required...

To answer your question it probably protects the tool mfg from mis-applied hot and neutral wires. Consider the case if someone wired the receptacle opposite from convention with the hot wire landed on the large socket....then the hot and neutral are confounded and the entire chain is now energized all the way thru the motor and over to the switch.

 

[MikeF2316]

Exactly. But you can also wire the poles in parallel for 120v use and double the current capacity. Makes the switch last much longer.

Now this is a hell of a good idea. I've already replaced the switch in my drill press once and noticed it switched both hot and neutral. Tomorrow I'm going to change that!

 

[dogdog]

....... I don't think it is current capacity issue for having a DPST on these , might be more for safety...

 

[exmaxima1]

....... I don't think it is current capacity issue for having a DPST on these , might be more for safety...

Definitely safer to use both poles when you have an old 2-wire power cord, but if a modern 3-wire cord was added (as well as contemporary receptacles) you don't need to switch both poles.

 

[MikeF2316]

....... I don't think it is current capacity issue for having a DPST on these , might be more for safety...

When my switch went, I was using a hole saw. It jammed up and both the piece was solidly clamped down and the belts were tight enough so the motor stalled. It wasn't a second like that before I released the pressure, but one of the switch contacts had melted. Interestingly it was the one on the neutral side. The breaker didn't trip, although I had tripped the breaker with the drill press previously. I was able to join the neutral wires together and keep working (with a little less pressure on the hole saw) until I bought a new switch.

 

[m32825]

Thanks to all for their contributions, I learned something new.

Here are a couple pictures. Hot and neutral each feed the switch and one side of the light circuit. To rewire it to switch hot on both sides I'm thinking I need to tie all the neutrals together, then come up with a way to split the hot on the supply and load side. Sound right?

-- Carl

 

[MikeF2316]

Thanks to all for their contributions, I learned something new.

Here are a couple pictures. Hot and neutral each feed the switch and one side of the light circuit. To rewire it to switch hot on both sides I'm thinking I need to tie all the neutrals together, then come up with a way to split the hot on the supply and load side. Sound right?

-- Carl

If you're talking about doing what exmaxima1 suggesting (and I've since done) is connect all the white wires together, then connect the switch terminals that are side by side together. Mine has a ground wire, and I made sure the white wire really was a neutral.

 

[m32825]

If you're talking about doing what exmaxima1 suggesting (and I've since done) is connect all the white wires together, then connect the switch terminals that are side by side together. Mine has a ground wire, and I made sure the white wire really was a neutral.

Yep, that's what I want to do. I got out the multimeter and found continuity between hot/black and neutral/white. Time to do some crimping!