What does this control do ?

[Brian JohnParticipant @brianjohn93961]

1. What does this control do ? This is a photo of an Optimum TU-2004V lathe ; it is the big brother of the small lathe I have now.

2. Do you think having two emergency stop buttons is really necessary ?

[Brian JohnParticipant @brianjohn93961]

This is from an Optimum TU-2004V lathe

[John RuddParticipant @johnrudd16576]

1) Is a thread dial indicator, used in screwcutting, to determine the engagement point when returning to the start of the thread after the initial and successive cuts….

2) The requirements for the number of controls is driven by some European directive for machinery, there is an Emergency Stop button at the top, then there is a No Volt Release switch below it, which just happens to have a Manual Stop associated with its functionality…my guess is these controls are in place due to the requirements of said directive….My big lathe has the same controls, yet my Chester 9 x20 nor my Sieg mini lathe dont….

[Neil WyattModerator @neilwyatt]

The original design probably didn't account for many NVR switches coming with a 'e-stop cover' these days.

I expect they would do away with the one on top, except it would leave an embarrassing hole…

All explained here (clear as mud…)

Neil

[MWParticipant @mw27036]

Either that or they would need to fit a blanking plate, which would only add to the mystery i suppose.

Michael W

[JasonBModerator @jasonb]

Posted by Neil Wyatt on 10/07/2016 12:41:47:

The original design probably didn't account for many NVR switches coming with a 'e-stop cover' these days.

I expect they would do away with the one on top, except it would leave an embarrassing hole…

All explained here (clear as mud…)

Neil

I think its the other way around, they originally fitted the NVR switches with integral emergency stop but as they are a bit of a pain to lift each time you want to start the motor people took the E-stop cover off.

I have one of the first 280 lathes which has the E-stop integral with the on/off and no separate e-stop, they later added a separate E-stop and now have open NVR switch and the E-stop on the top.

J

Edited By JasonB on 10/07/2016 12:58:44

[Brian JohnParticipant @brianjohn93961]

I have taken the E-stop cover off my drill press because it just became too much of a hassle to use it. I really could not see the point of it because I can hit the red off switch just as quickly as I can hit the red button on the cover. I do not remove safety features lightly but when they interfere with the smooth operation of the machine then something has to be done. Others may have a different opinion.

I think the larger separate emergency stop switch is an excellent idea and should be installed on all machinery. The E-stop cover is a lazy solution.

Edited By Brian John on 10/07/2016 13:12:38

[Neil WyattModerator @neilwyatt]

If you look at the link In gave, the NVR one is better because it works fast irrespective of how fast you hit the button and will stay off. The other switch only works as fast as you press it, plus it isn't latching off – it only works like this because its in line with the NVR switch and trips it when its pressed.

There are arguments for both. The cover-type switches do mean you have to clear the e-switch before being able to turn on while you can attempt a start with the other type of e-switch pressed in.

The fail-safe or not nature of these is different depending on whether they are directly wired or controlling an inverter, for example.

Neil

[John RuddParticipant @johnrudd16576]

Posted by Neil Wyatt on 10/07/2016 17:25:46:

The other switch isn't latching off –

Neil

Well I can assure you that on my Toolco lathe (same as the Warco WM290V and other clones) the Emergency Stop button does latch….

Neil, If you have an example of a machine where this not the case but is upstream of the nvr switch then it is of no consequence I guess…

My only gripe is that the ES is badly placed…..it ought to be within easy reach of the operator without having to reach over a rotating machine …….

[JasonBModerator @jasonb]

Yes if you look closly at the top of the E-stop in Brian's pic you can see the arrows where it has to be turned to unlatch.

I actually prefer the covered type NVR as your hand is used to going to that position to switch off the machine so in an emergency you don't have to think about where to hit as you instinctively go to teh usual off button but hit the cover rather than lift and use the stop button.

[AjohnwParticipant @ajohnw51620]

NVR switches have been a must for a long time. Good reason too. The kludge cover to make it an emergency stop switch as well was just done on many things for cheapness. Most people take the cover off. The nvr and stop button has been used in industrial environments for a long long time.

A stop switch is a different animal. They are forced rupture switches, or a least that's what I call them. The force on the button is directly applied to the switch contacts. The design lends itself to having a sensible latching mechanism and a nice big mushroom top that is hard to miss for if it's needed in anger. Also because the contacts are driven pretty forcibly they can have rather high current ratings. NVR's are often some form of latching relay set up so don't switch directly like a stop button can.

It's all similar to isolators using knife switches really. The same reasoning applies.

All that may have happened recently is that the same thing has been applied to hobby type items. Good idea too really as the cheap kludge method is a pain for people to use so the cover is very likely to come off.

I wonder if Brian is thinking about buying a larger lathe ????????

John

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Edited By Ajohnw on 10/07/2016 18:37:15

[Clive FosterParticipant @clivefoster55965]

Good example of how following safety rules and regulations actually makes things more dangerous due to the inherent confusion. Can't say that I approve of the latching type E-Stop switches as they effectively act as a disconnector once latched and appear to remove power from the machine. Bad on two counts:-

Firstly there is no clear indication that the switch has latched and is off. In the latched position the button is typically around 1/8" or few mm lower than normal. Not something easily noticed during the usual faff around working towards panic "Why won't the poxy thing go." situation.

Secondly without detail information on the circuits you cannot be sure where the power break of a latched E-Stop switch actually is so its quite possible for hurried folk to diagnose power loss due to internal problems and start investigating with power still on. Yes I know you should make sure everything is off before digging in but flustered folk can, and do, make silly mistakes doing things which normally they would know not to attempt. Even skilled help bought in to do the job can do silly things it not given all the information on the basis of wrong ASSumptions. Both places I've been in somewhat different situations. Regulations say that microswitches should be included to interrupt power if panels are opened but such things are regularly disconnected or otherwise circumvented by folk who just want to get on with the job.

The red stop button cap on the NVR switch raises the concept of kludge a little further towards an art form.

The rule framers seem to think you can inconvience people into being (theoretically) safe. A dubious proposition if ever I saw one. Unless the intention is to make folk think that using a lathe (or whatever) is just too much trouble.

Hard to beat the set-up on my Smart & Brown 1024 VSL. Proper disconnector on the main power feed. Big red lever on yellow background so On – Off status is visible from right down the other end of the workshop over 20 feet away. Machine has NVR relays on all controls with shrouded pushbuttons to select forward or reverse drive and a big red mushroom headed non latching stop button. Stop button is over 2 inches diameter and falls easily to hand. Simple, straightforward and sufficient. Each control does one thing in exactly the manner you expect.

Clive.

[Brian JohnParticipant @brianjohn93961]

A larger lathe ? Yes…eventually. I am just looking a bit down the track. If my current lathe were to fail for any reason then I am not sure I would have it repaired. Having used this lathe for a while, I have a better idea what I want in a new machine. The safety switches are important and I do not want a lathe that only has the silly E-stop cover like my drill press as that would drive me nuts. I regard the larger, separate emergency stop button that has to be turned to be released as a must-have item.

[KWILParticipant @kwil]

Has anybody actually needed to hit the Big Red Button in anger?

[Martin ConnellyParticipant @martinconnelly55370]

Brian John, I have sent you a message, please check your inbox.

Martin

[Anonymous]

Posted by KWIL on 11/07/2016 10:51:22:

Has anybody actually needed to hit the Big Red Button in anger?

Yes, when I got my jersey caught in the lathe power feed rod. Except that I didn't because I couldn't reach it.
Fortunately the normal power switch is on a lever on the saddle, so I used that. I could have used the 'stamp' bar, except that I forgot about it.

Andrew

[JasonBModerator @jasonb]

Posted by KWIL on 11/07/2016 10:51:22:

Has anybody actually needed to hit the Big Red Button in anger?

I hit the cover of my NVR the other day but it did not stop the internal threading tool I was using from Bending! On the plus side the insert was not damaged.

I have also had cause to use the one on my table saw a couple of times, luckily that is ideally suited to be operated with the left knee should your hjands be ocupied.

[AjohnwParticipant @ajohnw51620]

The reason for the nvr latching kludge is the manufacturers not the rule makers Clive. They would have argued that the correct solution of keeping a master stop panic switch separate to the nvr switch was too expensive for consumer items or needed to be introduced slowly. There is also a chance that there was a hole in the rules but I doubt that.

Given the nature of the areas I have worked in I have been asked to do all sorts of odd jobs at times as they haven't a clue who else to give it to. One of the jobs was a couple of panels. Both had to handle potentially high currents from batteries. A mix of electronics, electrics and mechanical work. I was told to go talk to a man who was a fellow of the IEEE and as I wanted to rewire a house as well we talked about that too. Years before it was fully implemented he knew all about earth bonding and various other changes to the wiring regs because much the same was going to happen in factories at some point. They take a long times to come up with these rules and in many ways it's the people who have to implement them that actually come up with and talk about the details not some rule maker. One of the side effects in many areas in my view is that the rules can tend to normalise things in an odd sort of way – manufacturers of one sort or the other worry more about meeting a standard than offering the best they can easily achieve because more people want what ever it is to be even easier.

I can't remember him mentioning 6mm earth bonding at gas meters. Electrical wiring safety is on odd one though as mishaps have slowly been knocked on the head and I suspect they are now down to things that don't actually happen and are getting more it might happen. On the other hand maybe lack of bonding there has caused problems. I suppose with a short some where it could.

One exception to a certain extent I suspect is outfits like TUV and Thatcham. The times Thatcham give for car repairs are way way over the top. That's why insurers have their own repair centres and pay the workers large bonus's for beating them very significantly without any real effort at all. That one they had to agree with the industry. I'd guess that there are other areas like this where both of them have to as well.

John

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[Neil WyattModerator @neilwyatt]

Clive makes some good points.

I caused posts by confusing the mechanical latching of the E-stop with the electrical latching of the NVR.

As John points out the mushroom E-stop can potentially be used to interrupt the supply without being depressed fully so it fails to latch if it isn't hit hard enough. This operates the NVR but then leaves a machine that someone can restart without having to 'clear' the e-stop by twisting it.

The combined NVR/Estop can also fail to latch, but at least the red button covers the start switch.

Of course with a big machine you will only have one NVR but may have several e-stops – many lathes have one on a foot-rail.

The drill I'm trialling at the moment has the e-stop positioned so you can operate it with your forehead, which has its uses

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 11/07/2016 17:14:29:

The drill I'm trialling at the moment has the e-stop positioned so you can operate it with your forehead, which has its uses

.

When the drill catches your tie, it automatically drags you into contact.

MichaelG.

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