Hi Robin the short answer , Yes many I should think……..b

ps my 1 pic is belt slip and releases both belts on an old Drummond……b

Edited By bodge on 03/05/2016 10:55:06

Edited By bodge on 03/05/2016 10:59:10

My Taiwanese lathe, with a 1.5hp single phase motor has survived over 20 years without a clutch, plenty of stop start work, is there something wrong with the motor on a Myford?

If I had a countershaft I would fit flat belt with a fast and loose pulley system. I would feel happier than using a loose v belt. Nothing wrong with v belt as a clutch, many ride on mowers etc. have them, my 6 hp rotavator has 2, been ok for 3 seasons. These do have guides to lift the belts clear when not engaged.

Robin,

"the Myford motor is a relatively crude capacitor start type "

Not quite fair as Myford always fitted top quality single phase motors to their lathes usually from Crompton Parkinson or similar British manufacturer. Capacitor start single phase motors are perfectly OK and the centrifugal switch is necessary to cut out the start windings as soon as possible as they otherwise overheat and burn out. As I said it is necessary and not a sign of cheap or incompetent manufacture.

The weak link in the original Myford set up is the wretched Dewhurst switch which is much more likely to fail rather than the motor. They survive better if the operator moves the lever quickly. but is much better to use them only as a change of direction switch is series with a proper DOL starter.

When I had a Super 7 I would leave the motor running and use the clutch except, obviously, when making measurements, changing clutches, etc. I did this in the belief that capacitor start motors did not like being switched on and off. Over the nine years I had the lathe, which was well used by me, I never had any problems with either the clutch or motor. However I did have to replace the belts.

Since getting a Myford Big Bore lathe fitted with an inverter I use the clutch far less often, happily switching the motor on and off when required.

I consider the Dewhurst switch very unsafe and would not entertain using one. I am a person who uses the big red button as an isolation switch.

JA

There was an excellent article in MEW years ago on making a clutch for an ML7 Neil will have the details. I and a few more close by, each made each ourselves a clutch following the instructions, very good. As mentioned earlier, the Dewhirst switch was just inadequate for the job as ON/OFF, no No – volt release either. Get a direct on line starter and then use the Dewhirst. People get anxious over reverse, but how often is it actually used ? John

I think that the long time period between forward and reverse, is simply to ensure that the motor has come to a dead halt. Going directly from forward to reverse on running motor is called "plugging" and causes enormous inrush currents to flow round the motor circuit. Not good for invertors. The electronics can change the phases around in a few 100s of mS without any harm to itself.

I have read a lot of bad comments about the Dewhurst switch. I reckon that you should use it to drive a pair of interposing relays with mains coils that it last would forever. The problem with all switches that drive solenoids and motors is when the contacts open, a very high voltage arcs across the switch contacts as they open. This causes pitting and smoke deposits as they get worse, the contact area gets smaller, so in the end they overheat when they close due to the current flowing through a very small contact area.

The high voltage arc can be reduced to virtually zero by the use of a "snubber" network. across the contacts. This is a high voltage capacitor and a low value resistor in series. Should not cost more then £2 each .A simple version can be made without the resistor, only the capacitor at a cost of about 50p each.

Frank

Are you suggesting taking a cut with the lathe in reverse? On my Super 7 the chuck was just screwed onto the nose of the spindle. There was nothing to stop it unscrewing when reversed. The Big Bore lathe chuck has a grub screw that engages in a grove on the nose to prevent accidental unscrewing.

I am traditionalist and the only justification for a reverse is to return the tool to the start of the thread when screw cutting and one has not got, or not got confidence in, a thread dial indicator. I would not dream in taking a cut in reverse on any lathe.

JA

Coming in late on this thread………

I was looking at an automotive air-con compressor the other day on my Ford V8 and it occurred to me this has a sort of dog clutch operated by a 12V solenoid. Not sure how much power/torque these can handle but scrap air-con compressers must be quite easy to find in scrapyards. I wonder if anyone has tried using one?

MEW 159 (Jan 2010) has an article by Ken Wilson on fitting an electromagnetic clutch to a Harrison M300.

I looked at this with a view to fitting one to my Warco GH1330 but after some thought I decided against it. The problem with this type of clutch is that the take up is almost instant whereas with a cone clutch you can feed in th power slightly more gradually.