ML10 Dewhurst / Brook Crompton

[starjumpParticipant @starjump]

Hello,

I’m getting on with jobs on the Myford ML10 which is new to me and am looking to site the Dewhurst switch. Before I do, could anyone please tell me whether the Dewhurst Forward/Reverse switch and Brook Compton single phase motor combination, is still an acceptable method of running a lathe.  Any comments around this subject will be helpful.

I will say that at this point that I still have to run the lathe, but the seller’s story suggests a low hours model, the contacts in the switch don’t look bad, and I would rather start off with the current arrangement if possible.   I am sure that variable speed, new motor and inverter would be a huge boon, but I’d like to start off with what’s here and then potentially add to it in the future.

It’s in need of a mains plug, the mains cable goes to the Dewhurst forward/reverse switch. Then  an armoured cable connects the switch to the motor.

Should I have an emergency ‘STOP’ button?

Thank you. Best, Starjump

 

[bernard towersParticipant @bernardtowers37738]

Robert has obviously not seen this yet but when he does you will have all the info you need

[starjumpParticipant @starjump]

Here’s the switch:

[starjumpParticipant @starjump]

@bernardtowers37738 Thank you!

 

[Clive FosterParticipant @clivefoster55965]

The Dewhurst is a direction switch, not a stop start switch. In practice perfectly compliant with modern safety expectations if used for that job in conjunction with a No Volt Release device to do the actual starting and stopping after the direction has been selected.

Whatever any theoretical non-compliance may be dredged up in the minute detail of the regulations a Dewhurst in decent condition and properly installed is a darn sight safer than the common cheap import forward-reverse / stop start devices. Although I’ve used them in extremis I’ve not been happy with what I’ve seen on teardown inspection of failed units.

Objectively the correct way to do the job is with remote buttons linked up to an interlocked reversing dual contactor unit. Maybe £70 all in including proper shielded push button units. More if you need a box rather than, as I would putting it in tech cabinet with cover.

Next best is a proper stop start box with name brand contactor inside, Machine Mart are relatively cheap and of respectable quality, followed by the Dewhurst.

Its sensible to add some form of foot bar operated emergency stop system. easily done with proper contactor systems. Impossible with the inexpensive imports. I’ve never worried about not having an emergency stop bar in over 50 years of machine work. But it is the sensible thing.

A major advantage of a Dewhurst is that everything can be inspected and any potential issues, whether wiring or contact related easily seen. They are also really durable even if grossly abused. For example by folk using them as stop start devices.

Clive

[BazyleParticipant @bazyle]

There have been wuite a few threads on here about motor switches. You need a ‘no volt release’ (NVR)  switch to turn it on and off and only use the dewhurst for isolating and selecting reverse to save sparking ruining those lovely clean contacts. And it is a safety device and some on ebay come with a big red off switch.
There is a variety of NVR switch that comes with the contacts for the built in relay available on the outside so they can be connected into safety switches on the shcuk safety guard etc. I posted some pictures only last year so must be still around on the site somewhere.

[noel shelleyParticipant @noelshelley55608]

DO NOT use the dewhurst as a start /stop switch and in an idea world a DOL/ contactor with a suitably rated overload device is best. This can then have panic buttons/emergency stop as part of the set up. Cheap Novolt units may take the run current but will not be happy with the start, the relay contacts will soon burn. Noel.

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