Safety emergency stop switchs

[DullnoteParticipant @dullnote]

Hi I was working away in the workshop after doing a safety check at work, notice lathe has no safety switch milling machine has push next to start, nothing in easy reach.

What do other have I was thinking a waist high bumb switch easy reach and can be used without hands, or foot switch.

Just wanted to see other ideas

Jim

[DullnoteParticipant @dullnote]

[Jon GibbsParticipant @jongibbs59756]

Hi Geoff,

On my lathe I have a cheap DOL starter from Toolstation in-line with the Dewhurst drum direction reversing switch but it has a small off button. So I wired up one of these also from Toolstation in parallel with the stop switch…

This one latches but it's not strictly necessary.

I need to do something similar on my mill but haven't got around to it yet. It doesn't even have an NVR switch!

Jon

Edited By Jon Gibbs on 18/01/2017 21:00:13

[Neil WyattModerator @neilwyatt]

Some of our advertisers do combined start/stop switches that may also be useful.

Neil

[AjohnwParticipant @ajohnw51620]

Lots of new machines come with emergency stop buttons. Some come with an NVR switch with some sort of latching cover. The cover usually has to be lifted up to start the machine. When the cover is latched down it holds the off button in.

There needn't be that much difference in what the 2 types can do but it depends on the type of switches used in the nvr and how they are wired. Th E stop button should directly force the contacts apart. The general idea is that they should still work even in fault conditions. They are there for panics so only break power when there is one so should last a long time without any problem. The other type using some form of NVR are usually used to start and stop the machine all of the time.

Some machines do seem to come with the NVR type. Lathes always seem to come with the emergency stop button. When I have something with the NVR type I usually take the cover off 'cause the cover has to be lifted to turn it off in the normal way as well as when I start it. My bandsaw has one. I suspect there may be some rules somewhere concerning items that can be sold with these fitted. A pultra lathe I have had been fitted with one because it's cheap. The cover soon came of that.

Either way some other switch is needed somewhere to isolate the lot. Might just be a switch in a 3 pin plug socket however a factory etc would have a full blown isolator – big metal box with a lever on the side. Also an emergency stop button and start stop buttons on the machine that are usually arranged in an nvr fashion. Should have said always really so that if the power goes it doesn't just start up again. In many cases they wouldn't just rely on what was built into the machine and add an nvr switch as well.

John

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[DullnoteParticipant @dullnote]

Hi John, my main point was if something get caught in the turning part of the machine, I could be in a position not to be able to switch it off, so looking at best method of a emergency stop

I was thinking about a bar about waist high at front of the units anything going wrong press the bar and machine stops, but I have to found anything like is in the normal internet sites, just wondered what other do

Jim

[Mike PooleParticipant @mikepoole82104]

I feel that a means of stopping a machine using a part of your body that is probably not involved in the crises could be quite useful. As we are likely to be alone in our workshop it will be up to us to shut things down safely in the event of the unexpected happening. As our feet are not usually doing much a foot operated stop can be useful, I worked on a lathe with a combined foot stop and brake which was very nice to use. Drilling machines can often occupy both hands and it can be difficult to let go, so a foot or knee or head stop could be useful. A mill could benefit from a few easily reached stop buttons as the working position can be to the left right or front. I did think of feeding all my machines from a lockable stop when my children were small but they were never interested in the workshop and I never got around to doing it.

Mike

[Ady1Participant @ady1]

I have been using remote controlled plug sockets like these for a few years now, also saves me bending down to switch stuff on and off around the workshop

…I like to be able to run away as well as switching things off…

You can put it on a cord around your neck or keep it close at hand

They are a bit like car key fobs and use unique programmable digital numbers

Edited By Ady1 on 19/01/2017 00:51:53

[“Bill Hancox”Participant @billhancox]

In one of my previous lives as a safety officer, we referred to these as "bump switches". In one building, all floor mounted power actuated tools had these mounted at roughly knee height in such a ways as to enable the operator to easily bump it in an emergency. Very handy when one appendage is bleeding and the other is attempting to stop it from doing so. The bump switch was kept in a depressed (OFF) position when the tool was not in use and had to be pulled out in order for the actual tool switch to function. This also helped prevent unauthorized persons who were unfamiliar with the switch sequence from using the tool.

[HopperParticipant @hopper]

Posted by Ady1 on 19/01/2017 00:49:49:

…I like to be able to run away as well as switching things off…

What steps do you take if you find the boiler water level low and the steam pressure high?

Boiler room steps, two at a time.

[David JuppParticipant @davidjupp51506]

Posted by Jon Gibbs on 18/01/2017 20:59:33:

Hi Geoff,

On my lathe I have a cheap DOL starter from Toolstation in-line with the Dewhurst drum direction reversing switch but it has a small off button. So I wired up one of these also from Toolstation in parallel with the stop switch…

 

I presume this is actually wired in series​ with the stop switch. In parallel it would prevent the stop from working at all (both stops would have to be pressed to stop the machine!).

Thought I should highlight this in case anyone was planning to try this.

Edited By David Jupp on 19/01/2017 08:19:16

[Ex contributorParticipant @mgnbuk]

So I wired up one of these also from Toolstation in parallel with the stop switch…

Is this a typo ? Stop switches are usually "Normally closed" contacts & are wired in series.

Nigel B

(Just noticed that DJ beat me too it !)

Edited By Nigel B on 19/01/2017 08:04:11

[Martin KyteParticipant @martinkyte99762]

I have a emergency stop switch on the lathe (Newton Tesla drive) that is marginally helpful in as far as it's easier to hit than the normal stop switch in a panic and I cannot say I have ever used it. The Myford mill has a kick switch at floor level on the base which I use all the time to stop the machine as it saves reaching round the side to the starter. A floor mounted kick switch would be very handy on the Startrite drill press (something I've thought about but never implemented) as it's the only machine that you potentially have to stop when both your hands are in use. If you are drilling with one hand on the downfeed and the other holding the work (In a drill vise? ;0) ) and the drill stalls it's difficult to switch off without letting go of something. It has to be your right hand because the other is holding the work to stop it rotating and the switch is on the left side of the machine.

So in conclusion if you are starting from scratch you want a bump switch or kick switch on anything that ties your hands up. Fast access on anything that you walk away from when it's running and the most instant kill switch you can get on anything CNC.

regards Martin

[JAParticipant @ja]

After fitting a power feed to my milling machine table I put a bump switch, I call it a big red button, that cuts the electricity to both the milling machine and power feed. It seemed sensible to cut the power to everything but I have never used it. I do use the individual big red buttons on the lathe and milling machine as a normal way of switching them off. Many years ago I was told this was bad practice.

I would like to fit a foot operated treadle switch (I think that is what they are called) to the lathe but never had a close look at such a set-up.

JA

[john fletcher 1Participant @johnfletcher1]

I have a 240 volt single phase contactor which controls all the socket outlet in my workshop (but not the lighting) and have several locking type stop buttons at about waist high around the shed. All stop buttons are connected in SERIES, so that when any one of them is pressed all the power is switched off. All the lights are operated by pull switches. I have three inverters and each has a 20 amp relay in front which gives protection on or after mains failure. Also I have separate equal potential bonding, one machine to another not relying on the 13 amp plug earth connection alone. For the drilling machine I have a foot operated switch, I have to have my foot on the switch for machine to operate, should things get out of control, walk away. John

[Brian WoodParticipant @brianwood45127]

For many years I have used a hinged Dexion angle iron across the front of the machine bench that operates a 'twist to release' stop button. That is in turn wired into to OFF circuit of all three identical no-volt DOL starters that serve the bench drill, lathe and mill.

​In the event of a jam, seize or whatever calamity I can just lean in the rail, rather in the method of a crash bar out of public buildings and all three machines are disabled until I release the switch. Visitors, leaning forward for a closer look often trip it, but it has saved the day on a number of occasions and was well worth the effort in setting it up.

​A variation could be built around a pull switch with a safety cord through eyelets to go round a corner.

​I fully commend the idea to others

Brian

[AjohnwParticipant @ajohnw51620]

John F's is more like what has to be done on bigger machines. I was thinking in terms of stuff that can run off a normal 3 pin plug as a panic button is fine for breaking that circuit providing it's current rating is high enough. A lot of them are 10A though. Personally as long as these only break current when there is a panic I think they would be ok even at 13A via a fuse.

Don't take any notice of me though. It's your choice. Max power in my case is 1hp so say may be 2 going in.

When a contactor is used for higher currents it finishes up like an NVR switch. Some how energising it holds it in. That could be done with an NVR switch, A panic button can then be added to the power to the nvr switch also any other safety switches in series.

This shouldn't really be used to start and stop the machine. Either the controls on it or even an inverter should be used. If something needs to added it should be an on off switch unit with adequate current rating.

In my youth I did a big box to do this sort of thing with massive contactors capable of switching several hundred amps and breaking a lot more. As it was all in one box I used 240v AC contactor coils to save adding a low voltage supply. The were single contact units that even had arc shutes. They were held in with a latching relay – a normally open contact pair is simply used to energise the coil when the relay is pulled in. I used normal relays for that because I thought the current levels and sparks when they opened and the wiping action when closing would keep the contacts clean. It didn't. They all passivated in a couple of months so had to fit gold flashed one. Those went on working for years. Just in case some one does a complete diy job. While 100ma or so may sound ok in this case it wasn't. On a later similar job I did use a low voltage supply and smaller relays. I liked the octal base type on the first job as it just needed round holes. More sexy too.

I use the inverter as an NVR on my lathe and for control just as the manufacturers recommend. My miller isn't fitted with one. It's 1/2hp so should be fitted with an on off switch box with nvr built in. To be honest I personally don't see a need for a panic button on this. It's a small machine, (Dore Westbury). Having seen a rather large millers castings crack when some one walled away and left just the feed on I'd choose a wiring method that didn't allow that to happen. Maybe limit switches too.

John

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[Ian S CParticipant @iansc]

The workshop at the local high school has a system in both the metal, and woodwork shops of a network of ropes strung around at about 2m height so that from anywhere in the workshop the entire workshop can be closed down with one pull, not quite what you would have in a home workshop, but very handy if you are trying to supervise 30 kids.

Ian S C

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