Welcome to the forum Chris. How post photos described here.

First step is to identify the type of motor, for which pictures will probably be necessary unless someone recognises the Delco part number. As the motor could be old, it's Sherlock Holmes time.

Particularly useful is a photo of the terminals inside the terminal box, which should have a removable cover. If not, the motor will be hard to reverse because reversing is done by swapping over one of two pairs inside the cover. The exact wiring depends on the motor – there are about 4 different types.

I'd put the Dewhurst in a museum, or sell it to a Myford enthusiast who wants an authentic look. They weren't particularly good switches when new, so replace it with a modern one.

If the motor can't be reversed and it matters to you, John's suggestions is a good one – replace with a 3-phase motor and VFD, kits available with instructions. You get smoother running, speed control, and reverse.

Dave

Welcome to the party Chris !

The dewhurst is easy ! Top left is No1 Live in, No2 Start winding, No3 Neutral, No 4 unused. Top right No5 run winding, No6 Start winding, No7 Run winding, No8 unused.

No 2 & 6 may have to be swapped for the switch to show right ! There are many colour codes and terminal names so tell us what you have and it should be easy. Best wishes Noel.

Before you spend/waste any time wiring in the ancient Dewhurst switch, carefully inspect the contacts inside the switch. They commonly burn out and become unusable over time. That is quite possibly why the previous owner bypassed the reversing switch.

You don;t really need reverse on a hobby lathe. I have used my old Drummond lathe for over 50 years without it. I have reverse on my ML7 but have never once used it. The only time you might really need reverse is if screwcutting metric threads on an imperial lathe.

You might be better off to leave the reversing switch until later and carry on without it. Wiring in a simple stop/start push button switch (available online cheap) would be a good safety thing though. As a beginner there is plenty more you need to do and learn first before really needing reverse.

A close inspection would seem to show the start windings are tapped from the run windings – this being so then reversal in simple terms is not possible. But it appears to be only 1/4 Hp ? if so then it is to small, n S7 should have a 1Ph 3/4Hp or 3Ph 1/2Hp. Wire it up as shown on the cover with out the reversing switch and play with it.The important thing is to make sure it has a good earth connection.  The machine will not take heavy cuts and may not run at top speed but will give valuable experience. DO NOT overload the motor or you will quickly cook it ! When money is available look for a secondhand 1ph motor, there should be many about as everybody changes to VFDs with 3Ph. If there is plenty of money then you may consider a VFD, though I have 2 S7s and have no intention of changing. WHY VFD ? Variable speed, handy bit in no way vital. Reversal of direction, on a lathe with a screw on chuck ? Smoother drive, theoretically correct ! A very complicated electronic kit with plenty to go wrong and need setting up, unlikely to be happy in a damp shed. Costly, new motor and unit ! You must choose ! Good luck, Noel.

Edited By noel shelley on 08/05/2023 10:58:34

As there doesn't seem to be a capacitor it is presumably a motor where the start winding just has a high resistance compared to the run winding to give some phase shift. With only 1/4 hp the lathe is definitely underpowered. And apart from anything else the mains cable looks old and horrible and ought to be replaced!

I fitted a 3ph motor to my S7 only partly for variable speed, but mainly to get smoother operation. With the single phase motor the higher speed range on the motor pulley was essentially unusable as the lathe vibrated so much. Going to 3ph has transformed the machine, much smoother and quieter. Single phase motors inherently have lumpy torque.

I agree reversing this motor is likely much more trouble that it's worth.

Only three terminals in the box and a diagram showing the start winding is tapped into the run winding mean this design isn't simple to reverse! Unlucky: it's more usual for the both ends of the start winding to be brought out to terminals, and these are easy to reverse once the terminals are identified.

The photo is blurred, but as Bazlye says, ¼HP is the bare minimum power for a lathe of this size. ½HP or ¾HP is more usual. 1HP is a shade too much poke, and more than 1HP unwise because of the high wear rate and risk of damage when the lathe is crashed.

That a Super 7 won't run in reverse isn't a huge problem, and many owners with reverse avoid doing so because it risks unscrewing the chuck. Lathes with bolt-on or cam-lock chucks do forward and reverse equally well, which is very useful at times, but not essential.

The machine will work plugged into an ordinary mains socket, but this is bad practice today. It's usual to fit a combined Emergency Stop / No Volt Release switch. Various, styles such as:

The big red emergency stop button is wonderful if the operator gets caught in the works, especially if wifey has to rush in and cut the power. NVR stops the lathe restarting unexpectedly after a power cut – a common cause of accidents. Look for NVR on the internet – widely available from Amazon and others.

Dave

Can someone explain how any of the many earlier model engineers using Myford 7 lathes with a single phase 1/2 or 3/4 HP motor were able to build such accurate and functional models ?

Emgee

Edited By Emgee on 08/05/2023 11:33:04

By the superhuman greatness of all things Empire and ancient. Kings in golden carriages and Manx Nortons and all that.

And by rubbing a block of wood against the chuck to control its movement.

I fitted a very similar looking motor carrying an AEI Houston label to mine, three phase with a VSD but 2 pole to rev the old girl up a bit. Very successful, until a small but persistent spiral of swarf managed to make its way through the ventilation hole next to the terminal box.

Sparken blitzen mit ausgepouf.

It needs its ventilation but you might like to cover the hole.

HTH Simon

PS I wouldn't question 1/4 HP – yet. Plenty of umph to get into trouble, run it and learn its limits for a while.

That is why I fitted a TEFC (totally enclosed fan cooled) motor to my ML7. The most basic safety assesment would say "nein" to any motor that was not fully enclosed anywhere near a lathe.

That rubber mains lead really needs replacing. Use crimp ring tags on the replacement and make sure you leave the earth connection a bit longer than the live and neutral. This is so it does not get pulled off first if the cable is yanked. Even more important than usual as the terminal box does not seem to have any strain relief.

Robert.

Edited By Robert Atkinson 2 on 08/05/2023 13:44:29

Edited By Robert Atkinson 2 on 08/05/2023 13:45:03

Makes no difference.