Magnetic starter switch

[Bob Hallowell]

I have been trying to figure out a safe way to put a STOP switch on the rip side of my tablesaw. I have a sctw deluxe saw and the switch is off the the left hand side which is nice for crosscutting I can bump it off with my knee. But when ripping It's not so easy. I was thinking of putting a momentary mushroom type emergency off buttom on the incoming power and mount it under the saw closer to were I stand to make a rip cut. Will it work?

[Matt Meiser]

I doubt you'd find a momentary PB that would handle the load for very long. But you could put one in series with the existing one in your existing controls, assuming it has one.

[Mark Engel]

Bob, I finally got around to answering your question on the post about the safety switch.

When I made the knee kick switch for my Grizzly 1023, I relocated the switch from the left side of the cabinet to the right side. With the switch located on the left side of the cabinet there was too much flex in the 3/4" pvc pipe to make it effective from the far right side. With the switch re-located to the right side of the saw cabinet the actuator was closer to the center, making it a bit stiffer.

I don't know if this makes sense the way I have tried to explain it. I am not an engineer.:o

[Bill Huber]

Everyone talks about Magnetic starter switch and I am not sure just what they are...

But if you took a relay that would handle the current that is needed and had one set of the contacts as a lock for its self then you could use just about any switch you wanted as a stop switch.

[Tom Henderson2]

Everyone talks about Magnetic starter switch and I am not sure just what they are...

Hi Bill-

The magnetic switches require power to keep them in the "on" position.

This is a safety feature; if the breaker blows or power goes out for any reason, they revert to the "Off" position.

With a conventional switch, if you are sawing away and blow the breaker, and don't think to manually turn the switch off BEFORE you reset the breaker, the saw will come on by itself when power is restored. As you can imagine, this can be a safety problem.

With the magnetic switches, when the breaker blows they automatically revert to the "off" position. That way, you don't need to remember to turn the switch off.

I hope this makes some sense. Mag switches are required in many commercial applications, and some of the larger power tools come with them installed. But we don't see them very often on hobbiest/homeowner tools.

-Tom H.

[Bill Huber]

Hi Bill-

The magnetic switches require power to keep them in the "on" position.

This is a safety feature; if the breaker blows or power goes out for any reason, they revert to the "Off" position.

With a conventional switch, if you are sawing away and blow the breaker, and don't think to manually turn the switch off BEFORE you reset the breaker, the saw will come on by itself when power is restored. As you can imagine, this can be a safety problem.

With the magnetic switches, when the breaker blows they automatically revert to the "off" position. That way, you don't need to remember to turn the switch off.

I hope this makes some sense. Mag switches are required in many commercial applications, and some of the larger power tools come with them installed. But we don't see them very often on hobbiest/homeowner tools.

-Tom H.

Thanks Tom, that means that a mag switch is no different then a relay like I was talking about.

87555

[Matt Meiser]

Yep, basically a big relay.

[Bob Hallowell]

I was thinking something like this it is a 240v 6amp, that souldn't were out should it?

ebay 380023589029
Bob

[Matt Meiser]

You want to put that on the incoming line? Or in series with the existing stop button?

[Bob Hallowell]

I was thinking with this on I would have to put it in series. do they make them say 15 amp? so I could put it on the incoming line?

Bob

[Wayne Cannon]

The contactor/relay in the switch carries the load. The switch only needs to handle the pull-in current of the contactor. A normally-closed (NC) momentary push-button wired in series with the existing off button will break the circuit when pressed (just as the existing off button does), releasing the contactor/relay and turning off the saw.

You could put a switch in series with the incoming line, but that would, indeed, need to carry the entire current of the saw, and would have to be designed to handle the unique starting current and arcing requirements associated with a motor -- which any switch designed for motorized equipment should handle with ease.

[Mike Canaris]

I wired in a momentary contact safety switch wired to the same 2 wires the "on" button engages. I usually tip it with my hip when I need the saw to stop.

http://img.photobucket.com/albums/v260/canaris/stops.jpg

[Alan Schaffter]

The real solution involves some of the principles mentioned here but goes one step farther- that is a low voltage control (LVC) like found on many of the older big Delta machines. Instead of a magnetic start switch that uses a contactor (relay) powered directly from the line current like most of the newer, all-in-one-box, magnetic starters, the contactor in a low voltage control usually has a 24V coil and a spare set of contacts for a "latching circuit". An LVC also needs a transformer to provide the 24V. With an LVC you only need low voltage momentary contact pushbuttons- one with normally open contacts (start) and one with normally closed contacts (stop) to control the machine. You can easily add any number of additional Start or Stop buttons to an LVC control, and each one will have full control. I added a single extra stop button and a knee kicker to my Uni and an extra Start/Stop combo on a stalk on my jointer. If shop power is interrupted, the machine turns off- the contactor relay opens and the latching circuit is broken- so it will not restart on its own. The Start button must be pressed again to start the machine.

[Jeff Bratt]

If you have a magnetic starter switch something like this (http://www.grizzly.com/products/Magnetic-Switch-Single-Phase-220V-Only-3-HP/G4573), then you could easily wire that pushbutton from ebay into its control circuit (http://www.grizzly.com/images/manuals/g4573_m.pdf) to allow stopping the saw from a "remote" location - just like Mike did. I'm pretty sure which connections would be used, but it would be best for you to get confirmation from the vendor of the actual starter switch on your saw...