Switch replacement questions for bandsaw

[Dan Hahr]

I've tried to find an exact replacement switch for a Powermatic 81 bandsaw I have been getting back in order. It currently has a good switch but I can't find a cover plate for it and it didn't have one when I bought it. The current switch is a momentary on off switch and its wired to a magnetic starter. I see a lot of old machinery wired to the relatively inexpensive switches available from Grizzly or Woodstock for around 15 dollars. However these do not appear to be momentary switches.

Is it necessary to have a momentary switch or will one of these work with the mag starter? Or is there a better solution that won't cost me a $100? I'm starting to think that I might make wooden one

Thanks, Dan

[Curt Harms]

As far as I know the switch for a magnetic starter has to be momentary. Grizzly does sell magnetic switches, the difference AFAIK is motor starters incorporate overload protection, magnetic switches do not. If you can't find a cover on Ebay or OWWM and the current starter is working, making one seems like the least costly option.

[Kevin McCluney]

Can you fabricate a switch plate from wood or plastic?

[Dan Hahr]

I am actually thinking of making one out of wood. A rocker with a pin through the middle of it and loose enough to just push the plastic buttons and return to flush will probably work fine. I think I'd rather have one a little sturdier and proven though.

Thanks, Dan

[John Coloccia]

Can you post a picture of exactly what you have? I'm having trouble envisioning what you have and what you're missing.

[Dan Hahr]

This is the exposed switch. Sorry for the close-up, but it is the standard electrical box size.

Thanks, Dan
switch.jpg

[John Coloccia]

Only 2 wires going to it, and it still works? I have to think that's wired to a magnetic starter. The way it's going to work is you have 2 momentary switches. One is normally open, and one normally closed. The normally open one engages the relay. Once the relay is engages, some of that power is looped back to the coil to keep it engaged, and THAT part is wired to the other switch, which is normally closed. When you hit that switch, it breaks the power to the relay, and the thing shuts off.

That's why I'm not understanding what I'm seeing. You should have at least 4 wires going to the switch and at least three coming from the starter.

Anyhow, one thing you can do is simply get two momentary switches and mount them to a plate you make. Something like these should work:
http://www.digikey.com/product-detai...002-ND/2747833
http://www.digikey.com/product-detai...003-ND/2747834

I'm not going to guarantee anything for function or safety since I'm only spending a moment on this AND I don't want anyone to hurt themselves. You need to examine this yourself, and examine your specific setup, including the requirements of your particular starter (I'm assuming there is one) and however much the coil draws. I believe the switches I linked to are good for 250V/16A, and I'm assuming that's probably more than adequate for your situation (I would guess the coil might draw an amp or so), but that's ALL just guesses.

So what I'm saying is I'm just tossing out a cheap, simple option, but you need to look at all of this yourself to make sure it's appropriate. I think I've sufficiently covered my rump.

[Thomas Hotchkin]

Dan
Who made your magnetic starter, any name in the starter box? This may help in finding correct replacement for your on-off switch. Check out this. http://www.ebay.com/itm/new-square-d...item5d51ed1f09

[Dan Hahr]

Hi, John,

Thanks for trying to help. Please forgive me for not painting a clearer picture. I had previously asked for help here on the forum regarding the wiring and received some good advice. But anyway, here is the background info:

There are three wires going to the starter, a black, red, and white(ish). The motor is 2hp, single phase. and wired for 230V. The black wire was taped off at the plug, but connected at the starter. The black wire goes to a part of the mag starter from the switch. The red and white are connected to the two NC terminals of the switch. The black is connected to the NO top terminal. There is a breakaway tab connecting the middle NO and NC terminals. The white is connected to the transformer side of the starter. The black and red are connected to the front of the contactor (I think that's what it is..) It appears that when I push the top button of the switch (NO) it completes a circuit between the red and black operating the contactor. I'm not sure when the white comes into play. I know when I hit the NC button, it opens the circuit.

The switch is a Furnas switch and I have found similar switches on Ebay with various part numbers. I'm tempted to buy one just for the faceplate, but if I did, I would want to know the switch was the right kind. None of the numbers on the switch match the Ebay listings.

I don't see how I could wire the basic DP/DT push button switches from Woodstock, Grizzly, etc. (https://www.grizzly.com/outlet/110-2...f-Switch/H8243) to work with this set-up, but I see a lot of tools that should have starters with switches like this one^^. I suppose I could remove the starter and wire it directly to the motor, but I like the idea of using the starter for the protection it offers.

I did not think about using two independent push buttons, but that seems like it may work. However, it appears that the white wire is energized when either of the buttons are pushed as they are connected with the break away tab. Maybe I just don't understand what is happening inside the switch.

I will attach some photos of the switch and mag starter. It is hard to get the black wires to show up in the photos. It is especially confusing since one of the wires is not carrying any load (the black from the plug to the contactor.

However wrong this may appear to be, it does in fact work. It did come with a four prong twist lock plug which I removed and replaced with a three prong NEMA 6-15p. I left the black out and connected the red, white, and ground, and taped off the black.

If you or anyone else can make any sense of this, please feel free to comment.

BTW, the wire from the switch is coming into the box from the bottom right knockout. The top right goes to the plug, and the bottom left goes to the motor.

Thanks, Dan



mag starter top.jpgbottom of transformer.jpgswitch closeup.jpgmag starter 2.jpgoverall.jpg

[John Coloccia]

I just couldn't see the black wire or the tab in the picture. So you have the 3 wires from the starter, and the 4 wires (connections, at any rate) to the switch I was talking about

I'm a bit busy at the moment, but if I have a minute I'll come back to explain what's happening

edit:
You know, I'm actually going to bow out of this one. I thought about it, and it's just too hard to explain the workings of a magnetic switch like this. It's not that they're complex, but they are normally designed in a very general way to accommodate different wiring schemes, thermal protection, etc and it's too hard to try and explain all the little connection, and the hows and whys of how they work. Maybe it will be sufficient if I just say this:

NO and NC stand for normally open, and normally closed. The white wire is likely always energized. The black wire eventually goes to the relay coil. When it's turned off, the red wire is just hanging out not doing anything.

When you hit the NO switch, it energizes the black wire thanks to that tab on the switch, activating the relay and turning everything on. This will also self-energize the coil and keep the relay closed. Essentially what happens inside the starter is that when the relay is closed, the red wire, which previously was doing nothing, ends up getting connected to the relay coil as well, so the white wire is now driving the relay directly through the red wire. When you hit the NC switch, you open the connection between the white wire and the red wire, denergizing the coil and turning the whole shebang off.

Clear as mud? If you look at the wiring on a starter, you'll wonder to yourself just how in the heck is the thing actually working, but it's only because you can't see all the little interconnects going on inside the starter.

Again, it's all just based on what I'm seeing in the pictures, so if you're not comfortable whipping out a meter, measuring things and looking for yourself, maybe it's best to just order a direct replacement, or make a little cover yourself as you had planned.

[Dan Hahr]

Yes, that's right. For some reason I was not counting the ground. The green ground is connected at the switch, behind it. I read your last post again and I think the clouds of fog are beginning to clear....

Thanks, Dan

[David L Morse]

This http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1 should do the job if you can tolerate the plastic box on your saw.

[Dan Hahr]

Thanks John. That's enough to get me where I need to be. I realize the switch I was referring to won't work and I think I found a nice Allen Bradley switch with two NO and two NC terminals. I might just make a wooden on for the time being and wait on a good deal to show up. Thanks again for sharing what you did.

David, I may end up getting one like that but I really would rather try and find a used USA made switch.

Thanks everyone, Dan