ML7 lathe

I have just acquired an ML7 lathe, it is in excellent condition and seems to work well. I am very much a beginner and I look forward to working on this machine. I note that although the control switch has a forward and reverse position the machine will only run in forward whichever position the switch is in. Do some of these machines not have a reverse gear. Dave.

Hello David

The "reverse gear" is done electrically and involves the swapping over of some contacts within the switch unit. It's quite possible that the previous owner has not wired it up that way, or has been obliged to omit the reversing facility as some of the contacts have burned out. If it's the usual Dewhurst affair then that's a common failure. It may even be that the motor itself doesn't have the necessary wiring in place.

I would look out for a ML7 Manual. I think I've seen one in pdf format on the web somewhere, but they're readily available. You ought to have one for setting it up and for routine maintenance.

Reversing an ML7 is also a bit worrying on occasion as the chuck can unscrew, which can lead to a furrowed brow as you examine your broken workpiece and the dents in the lathe bed. It's very rare that you should need reverse anyway.

Look out on the usual auction sites for a copy of Ian Bradley's book on the Myford lathes - a lot of good stuff in there too.

You can download an ML7 manual here

**LINK**

although you may have to register for the "myfordlathes" Yahoo Group first but that is free.

FWIW I installed a DOL starter between the mains inlet and the Dewhurst switch to save the contacts from being switched under load thus hopefully prolonging their life.

HTH

Jon

Oh - one other thing that occurs to me; did you let the motor come to a complete standstill before reversing it? If you simply flick from forward to reverse, it probably won't, but just carry on in the same direction.

Hello Nigel

Many thanks for your prompt response to my enquiry. I take your point about the chuck unscrewing, I was intending to use the reverse function to part off as I have read somewhere that it is safer and more efficient to do it that way.

I will take your advice and get hold of a copy of the manual. Can I definitely assume that my perceived problem is a fault with the switch or wiring and not the lathe or type of motor.

Thanks again for your help.

Dave.

You may be right about reading the advice, but I do not think it applies to a Myford or any lathe where the chuck screws on.

Perhaps you read (I'm guessing) that parting works better with the tool behind the work and the cutter upside down - as this allows the swarf to fall out more readily. And there may be other reasons ... The point is, though, that this method still relies on the lathe going round the conventional way.

Hope this helps

Regards, Tim

Reverse is handy even on an ML7 sometimes, such as when cutting metric threads on an imperial machine or vice versa.

In this case you want to reverse the lathe to return the tool to the start of the cut without disengaging the half-nuts. Under those circumstances there's no reason for the chuck to unscrew.

HTH

Jon

The Myford drum reversing switch supplied by Dewhurst cannot reverse a single phase ac induction capacitor start motor when it is running!

To reverse the motor it must first be switched to OFF and when it has completely stopped then the motor switch can be moved to Reverse. If you switch over whilst running forward it will continue turning in the same direction. The reason is that the Start winding has the centrifugal switch in series with it. So when running at full speed the start winding is locked out of action. The same argument holds for running in reverse, changing the drum switch to forward has no effect.

However, if you have a 3-phase ac induction motor, which the Dewhurst drum reversing switch can also control, then changing the direction whilst running can damage not only the motor but also the drum switch contacts and is not recommended. Always switch to OFF and then wait for the motor to come to a dead stop before switching to the other direction.

Edited By John Fielding on 16/02/2016 10:50:39

The Myford drum reversing switch supplied by Dewhurst cannot reverse a single ac phase induction capacitor start motor when it is running!

To reverse the motor it must first be switched to OFF and when it has completely stopped then the motor switch can be moved to Reverse. If you switch over whilst running forward it will continue turning in the same direction. The reason is that the Start winding has the centrifugal switch in series with it. So when running at full speed the start winding is locked out of action. The same argument holds for running in reverse, changing the drum switch to forward has no effect.

However, if you have a 3-phase ac induction motor, which the Dewhurst drum reversing switch can also control, then changing the direction whilst running can damage not only the motor but also the drum switch contacts and is not recommended. Always switch to OFF and then wait for the motor to come to a dead stop before switching to the other direction.

Edited By John Fielding on 16/02/2016 10:51:15

I have used a friends Myford S 7 with a Dewhurst swtich, but it also has a push button off on switch, the only time the Dewhurst switch is touched is for changing from forward to reverse after first pushing the OFF button, and the lathe stops. Normal OFF ON by push button only.

My own lathe is by push buttons with interlocks, top forward, middle OFF, bottom reverse, it's done 22 years starting a 1.5hp Sph motor.

Ian S C

You certainly do not want to load the machine by cutting metal whilst running in reverse. That is asking to unscrew the chuck, and damage to machine, and possibly you, that will result.

(My lathe looks like a newer version of Ian S C s, and has restraints for the screw on chuck)

Parting off using a back toolpost is better than using the front toolpost. The parting tool is mounted upside down, and the lathe is run in the normal forward direction. Capstan lathes, used in industry, nearly always had the parting tool, or form tools, mounted on a back toolpost. On my lathe, the back toolpost carries the parting tool and tools to front or back chamfer the work.

Running a lathe with a screw fit chuck (without restraints) is likely to be done only when running the screwcutting tool away from the chuck, to avoid disengaging the half nuts.

Howard

Edited By Howard Lewis on 03/03/2016 17:47:53