Drum Switch

[Roger HulettParticipant @rogerhulett83124]

The very old push button remote on/off switch on my little old horizontal mill has finally given up. On fleabay is a chinese drum switch 311429429528 it says forward & reverse. Would this be suitable as a replacement.

My mill currently runs in an anti clockwise direction,so the reverse facility would stop the LH thread nut on the arbour,spinning off.

[Roger HulettParticipant @rogerhulett83124]

[NJHParticipant @njh]

Probably not a good idea Roger. The thing is that, when starting and stopping the motor, there is likely to be arcing as the circuit is made/broken and this will quite quickly burn out the contacts. The preferred method is to make/ break the circuit with the correct NVR starter ( which will also break the circuit in the event of a power failure and prevent it starting again when power resumes and you have your fingers in the works!) The reversing switch is connected between the starter and the machine and is set for forward / reverse BEFORE power is applied.

Norman

[Neil WyattModerator @neilwyatt]

If you need to correct the rotation of your mill, this is done by rewiring the motor connections and will be no more (probably less) complicated than by bringing them all to a reversing switch.

Norman is right that a proper NVR switch would be a better solution for on off control.

Neil

[AjohnwParticipant @ajohnw51620]

Not so sure about that Norman. These switches are break before make for reversing direction however it is a good idea to pause in the central position until the motor stops rotating. The drum switch that was on my Boxford had always been used to start and stop the lathe and dates back to the 70's and still functions perfectly. I have no idea how old the one was on my MYford and no problems with that either. These were both Dewhursts which were made specifically for this particular function. I would just wonder if the Chinese ones are as well made. I'v had several machines with nothing other than Dewhurst's on and no problem with any of them.

If the mill rotates in a direction that causes a nut that came with it to unscrew I would have thought that the motor is miss wired in which case fitting a new no volts release switch and rewiring would probably be the simplest option.

Curiously enough the NVR switch on my mill has been failing lately, it doesn't always hold in so is being replaced with ebay 111272288798

John

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Edited By John W1 on 21/08/2015 18:38:01

[David Clark 13Participant @davidclark13]

Stationary engines do a nice drum reverse switch. Feed this from an NVR switch so the drum switch contacts do not arc.

[AjohnwParticipant @ajohnw51620]

Pity the NVR switch contacts which it seems must be arcing.

John

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[David Clark 13Participant @davidclark13]

It is a lot cheaper to replace the NVR occasionally rather than the expensive drum switch.

[John Stevenson 1Participant @johnstevenson1]

Posted by John W1 on 21/08/2015 19:16:29:

Pity the NVR switch contacts which it seems must be arcing.

John

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Considering that there must be billions of NVR switch world wide in everyday use they don't do bad.

Dewhust type switches are illegal today anyway so if you do want one for old times sake do as David says and feed it from a NVR

[NJHParticipant @njh]

OK John – so you are not convinced on the arcing question – your choice!

Far more important is to have an NVR switch in circuit. In the event of a power failure the switch will disconnect the motor from the supply until reset. If you feed directly from a reversing switch WITHOUT a NVR in circuit then a power cut will stop the machine. When the power is restored however the machine will RESTART – let's hope that no one is leaning on it etc. when it does so!

Norman

[John Stevenson 1Participant @johnstevenson1]

Posted by NJH on 21/08/2015 20:20:49:

OK John – so you are not convinced on the arcing question – your choice!

Norman

Which John, me John S, or John W1 ?

[AjohnwParticipant @ajohnw51620]

I did point out fitting of an NVR and a bit or rewiring would be the sensible thing to do but to be honest I have had so little trouble with drum switches, a big fat zero in fact, that if one of those was on a lathe I would put the NVR in circuit before it. My lathe is on an inverter now but when I just used the Dewhurst I also had 2 separate switches before it. Neither of these positioned so that they could be used to start and stop the lathe. They did prevent anyone from starting it "inadvertently". Personally if power fails I turn everything off and find out why not walk away and leave things turned on. I find it rather hard to accept that anyone in their right mind might do that.

I would strongly suspect that people who have problems with Dewhursts fail to notice that they no longer switch position in a rather positive fashion which probably means that there is something going wrong inside. Or perhaps people move the lever slowly. All I can really say on the subject is that there has been rather a lot of them about and I personally aren't aware of a single failure. I did nose about on the web out of curiosity – one person opened his and found it contained copper slip – that really does sound like a "great idea" barmy in fact. Another found something was loose and tightened it.

John

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[NJHParticipant @njh]

John S

It was John W1 that I was seeking to convince as he seems to be satisfied with a Dewhurst alone and was questioning my advice given to Roger, the original poster.

Me question or advise John S ? – it would be like questioning my wife's cooking ! ( It is VERY good and has turned me from the " 7 stone" weakling I was when I met her into the fine figure of a man that ( I like to think) I am today ! )

Norman

[AjohnwParticipant @ajohnw51620]

Posted by NJH on 21/08/2015 21:09:32:

John S

It was John W1 that I was seeking to convince as he seems to be satisfied with a Dewhurst alone and was questioning my advice given to Roger, the original poster.

Me question or advise John S ? – it would be like questioning my wife's cooking ! ( It is VERY good and has turned me from the " 7 stone" weakling I was when I met her into the fine figure of a man that ( I like to think) I am today ! )

Norman

As I read it Norman JS sort of agrees with me. They are amazingly robust.

John

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