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[Ken T]

I just bought an emergency Stop switch for a new lathe. Normally these things, well if your clothing gets caught, you hit the button and it stops the machine dead until you reset the button, but these clowns sent one that is non latching.  So you get caught in the machine, you hit the button, the machine stops temporarily, you move your hand to free yourself and the damn machine restarts and strangles you.

Why can't they copy things properly.

Ken

[Bent valve]

I just bought an emergency Stop switch for a new lathe. Normally these things, well if your clothing gets caught, you hit the button and it stops the machine dead until you reset the button, but these clowns sent one that is non latching.  So you get caught in the machine, you hit the button, the machine stops temporarily, you move your hand to free yourself and the damn machine restarts and strangles you.
Why can't they copy things properly.

Ken

That must have been a bit scary how did you recover from that

[Andy B]

.... but these clowns sent one that is non latching.  .....

Surely the 'Oh! Fu*k! Sh1t!' button is only to operate a separate brake system on the motor?  :-/
The lathe at the last place I worked at had a after market kick switched fitted on the floor in front of it that you stood on if needed. There was nothing to latch. The lathe at Heinz has a metal bar you kick, again, nothing to latch.

[Ken T]

Surely the kick switch latched, and kept the motor stopped until reset  ?.

OK, you are talking about proper multi horse machinery, I mean the small up to 1 horse stuff, the switch cuts electrical power and the motor stops quickly ( cause you are wrapped up around it  ) 

Noddy stuff has a zero volt type or latching switch that need to be reset to work after activation or power loss.

Ken

[Martian]

I just bought an emergency Stop switch for a new lathe. Normally these things, well if your clothing gets caught, you hit the button and it stops the machine dead until you reset the button, but these clowns sent one that is non latching.  So you get caught in the machine, you hit the button, the machine stops temporarily, you move your hand to free yourself and the damn machine restarts and strangles you.

Why can't they copy things properly.

Ken

Ignoring the fact that anything from China is the cheapest tat they can find, it sounds to me as if the switch is incorrectly wired.
The non latching isolators kill the power to the contactor coil, and this won't be restored unless you press the start button.

[Marks DTM Calib]

Yup, there normaly a push to break switch and little else which does as described above, breaks the contactor winding current.

I suspect its working correctly.

[Marks DTM Calib]

Heres some good info:

http://www.hs-compliance.com/uploaded/documents/THE%20EMERGENCY%20STOP.pdf

The resetting of the emergency stop device itself must not allow the machine to restart

So the latching types are not permitted when wired to simply break the mains supply as these could allow the machine to restart when reset. 

[mantahatch]

I have allways thought we have got it really wrong with stop and start switches.
I mean green to go and red to stop is all well and good for traffic lights, but for machinery surely turning the machine on puts it into a potentially dangerous condition, so you should push red to start it. Green on the other hand is viewed as safe so pressing green should put the machine into a safe condition, off.

Just my useless take on the world. 

[Martian]

I have allways thought we have got it really wrong with stop and start switches.
I mean green to go and red to stop is all well and good for traffic lights, but for machinery surely turning the machine on puts it into a potentially dangerous condition, so you should push red to start it. Green on the other hand is viewed as safe so pressing green should put the machine into a safe condition, off.

Just my useless take on the world. 

We have been doing it that way (red = on and green = off) for a couple of years or so now, although we are doing what we usually do and making the changes across the board slowly so that we end up with multiple colour schemes in use and then having to apply warning stickers to state the obvious.

[Ken T]

Thing is, its not big, a single phase CNC lathe, and the switch is rated at 10A, so I reasoned it would handle switching the main power feed, which is only a couple of amps without any contactors, zero volt reset stuff or the like.

http://cgi.ebay.co.uk/Red-Button-Machine-Tool-Emergency-Stop-Push-Switch-/290560482021?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item43a6c11ae5

I now discover another one with a turn to reset knob, using the same contact block.

Ken

[Marks DTM Calib]

I note the following in the item description

The mushroom push switchs are used in industrial controlling circuits for controlling in electromagnetic starter, Contactor, Relay and other electric circuits.

So its doing what it siad it should.

Do be aware that the latching ones dont meet the safety needs so probably only ideal for home use 

[Debs.]

I was sent a link to shockingly-gory pictures showing how deadly a large lathe can be.....

.......reliable emergency stop buttons/bars for machinery are absolutely essential!

[Ken T]

Yes, my original manual lathe is a mass of belts, pulleys, and screw cutting gears. The new one is totally enclosed, and you can't start it without the guard down.

Ken

[Ken T]

I note the following in the item description

The mushroom push switchs are used in industrial controlling circuits for controlling in electromagnetic starter, Contactor, Relay and other electric circuits.

So its doing what it siad it should.

Do be aware that the latching ones dont meet the safety needs so probably only ideal for home use 

I've just tested it, when stop is energised, the system does remove power and needs to be re- energised before restarting. However this about the latching knob not being OK, as the machine might unexpectedly restart when its released, well the reason you are releasing the stop button is to restart the machine, so you are expecting it to start, so....

Ken

[Andy B]

.... and you can't start it without the guard down.

Ken

This kind of thing drives me mad. You then try to look around the blasted thing instead of concentrating on the job in hand.  The miller at work has a box full of pressure switches etc wired in so that it will only start will compressed air on cos there's an air operated piston that applies the brake when you stop it. That and the bloody guards that are also wired into the start circuit so that you end up operating it from arms length or behind it (& the guard  :-?) so you cab get to the control panel  :-? :-? :-? The bloke that bought/commissioned it, didn't realise that all air in the factory was knocked off at the week end so a separate compressor had also to be bought & wired in. 
All in the name of safety!