Wiring Check

[flh801978]

If you want to install an emergency stop button you do need a starter like the one i linked to from screwfix though any electrical wholesalers will supply a suitable one..
This is because a momentary break in the stop circuit will stop the machine dead not to restart
If you just wire in a N/C (normally closed)switch into the supply line with your existing dol starter it will restart on letting go of said emergency switch
Emergency switches come in many different types simple flush stops ,mushroom heads that are sprung to go in at a trigger or large twist to reset types
H&S types prefer the twist to reset type with for added security a key switch in the middle
But on a table saw a type where you can hit it with your hip or a foot would be best

 

[jpor4180]

That's annoying, as I'm pretty sure that screwfix one is cheaper than the one I bought from Machine Mart

So the emergency stop wires in as the second DOL in that device you linked?

All this being said, with the inertia of a 10" blade my motor is going to take well over 10 seconds to stop I reckon. Takes a couple of seconds just for the spindle to come to a stop as is. Makes me wonder if an emergency stop would be of any use without a DC or EM brake

 

[flh801978]

Yes it will take a time to stop but at least you know when you have tapped the switch the powers off and the motor is coasting to a stop.
The starter that i linked to has a magnetic switch called a contacter which has a coil in it to suit your voltage
You energise the coil with the green start button which has a N/O contact then the could pulls in making the contacts to supply power to your load (motor) via a thermal overload which protects the motor. When the contacts make a spare pair in effect short the start switch therefore holding the large current switch contacts together.
When you want to stop the stop switches which can be remote break the circuit to the holding coil and then allows the switch to open.
The overload generally has a N/C within to de-energise the coil if that is overloaded
On the cheaper starters the green button actually pushes the contacter in rather than being a switch but you can always wire in a remote start switch too

Ian

Take the DOL you have back to MM

 

[sunnybob]

The No Voltage Release (NVR) switch is a device that is only held in the operating position by the electric supply.
If there is any electrical failure, even for a second, that NVR will disconnect. The saw will not receive power again untill you press the start button.

What you have there is an overload fuse connected to a very big contactor. If the power fails for any reason and the saw dies, that contactor and fuse are still ON.
It only needs you to start tinkering with the blade to find out whats wrong when the power comes back on and that saw will start up all by itself.
If that thought doesnt scare you nothing will.

 

[jpor4180]

Is there some kind of emergency stop button that can be connected to an electromagnet next to the blade, inducing eddies and bringing it to a stop like on a train?

Seems simple in principle anyway but I'm sure there are design limitations?

I'll get the new starter that can have the stop button put in, thanks Ian - and I'll also pick up a meter to check out my earth

As for the NVR I get how that would be a necessity in a shop with multiple people. I'm definitely glad I know I don't have it, and I'll cary on with my practice of unplugging a machine before putting my hands near the blade. I don't know if you do it too, but even if say the mitre saw is off, I just won't put my hand near the blade without seeing the plug

 

[tomatwark]

You can get a dc braking starter brooks make them.
They are about £400 and to be honest you don't need one, just get the correct switch.
DC braking is more about protecting the next person and also for machines that will run on such as tenoners and crosscuts.
On your own in your hubby shop this should not be an issue.
Dc braking will not stop you cutting your fingers off.
Using the machine correctly with proper guarding etc will

 

[flh801978]

Sunnybob
The DOL that jpor has is basically a 3 pole switch that's spring loaded to open and has a latch in the guts of it that is connected to 3 bimetallic strips which when you press the start button holds the start button in..if any of the 3 bimetallic strips which have a coil of wire carrying each phase gets too warm because of excessive current as set by the overload dial the latch is tripped thus switching off the current.
There's no contacter in it or magnetic coil making it independent of voltage used or supplied

As in earlier posts with sawdust Sam insisting that it was a proper contactor with NVR

 

[sunnybob]

There must be different types of those DOL switches then. There is one on my pool pump that looks identical. It does NOT disconnect when the power drops out.
We get lots of nuisance power cuts here and that thing is inside the electric pool box along with the timer and lighting transformer. We often know when power is restored because the pump starts up.
It only ever tripped when the capacitor went bad and the motor wouldnt start. Thats why i dont really believe its an NVR.
Yes, I DO switch off at the wall, even if I dont unplug. When changing bits on the router table I switch the wall socket off even though there is a fully working NVR on the table. Same with the bandsaw and mitre saw. I've seen many "ordinary" switches fail and always worked on the " 2 breaks" principle of keeping all my fingers connected.

 

[flh801978]

It's not a NVR I think we surely must have ascertained that by now !

Ian

 

[sunnybob]

sorry, I mis read your last post. I didnt fully read the line about the excess current. I told you i was asking questions, didnt I.

Yes, that tallies with my experience, so going back to the original post, I still would fit an NVR switch to any bladed machine.
The only saw that I know that stops dead if your fingers touch it is the sawstop. which is incredibly expensive and destroys the blade by firing an aluminium block into it when it senses your hand moisture.