# Union Graduate Lathe 3 phase vs single phase



## Rick2058 (26 May 2013)

I may be buying a Union Graduate Lathe with a 3 phase motor, would it be better to buy a single phase motor and fit, or to buy a inverter and keep the 3 phase, both ways cost about the same any advise welcome.


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## spinks (26 May 2013)

I would go single phase myself....not for any other reason than i prefer it!


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## mikec (26 May 2013)

Personally I would go 3 phase, smoother operation with speed controller by varying the frequency.


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## katellwood (26 May 2013)

Is the three phase lump dual voltage???


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## dickm (26 May 2013)

Having only used a Graduate in a class, I'm no expert, but the speed change seemed to be even more of a pain than on the Mystro. So if the motor is dual voltage, 3-phase seems to win hands down.


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## retreatjohn (27 May 2013)

Three phase with variable speed control,you wont regret it!


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## Naxie (27 May 2013)

3 phase every time, best thing I ever did to my lathe!

If you look here https://www.ukworkshop.co.uk/forums/union-graduate-t66355.html you can read a thread on which I posted my experience on the company I got my inverter kit from.

Also if you look here http://www.penturners.co.uk/your-tips-jigs/765-cheap-lathe-tachometer.html you can see a post I made today about fitting a cheap tachometer to said lathe.

Hope that helps,
Kind regards,
Ed


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## paul-c (27 May 2013)

hi Rick
for me it would definately have to be 3 phase and inverter.
i did just this using newton tessla to supply both the motor and inverter - and was very pleased with the result.
best of luck with whatever you decide.
cheers
paul-c


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## wizard (27 May 2013)

If its duel voltage go for the inverter, if its single voltage the inverter will cost more, but it will still be worth it.


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## graduate_owner (27 May 2013)

As has been said already, the 3-phase motor needs to be dual voltage (220 / 415) for it to work with any decent torque when powered by a 'basic' inverter (somewhere around £100 new, for around 2HP motors). If the motor is not dual voltage then you could buy a 415 volt inverter, but they are considerably dearer. Alternatively you could have the motor rewound. This is what I did for my milling machine. It was not actually a rewind, they just delved into the winding and picked out the necessary wires to allow me to connect to them. This work cost me about £30.

As to whether you would benefit from 3 phase - yes, definitely. I have a Myford ML8 which I have converted to 3 phase and the variable speed advantage is sooo worthwhile - especially when turning uneven / unbalanced timber. I still lose some torque at very low speeds but I can live with that. (Actually it's quite handy because if I get a dig-in on jagged baulks of timber then the motor stops safely.)

I have a 3-phase motor ready to fit into my own Union Graduate, and am looking forward to the upgrade.

Bear in mind that a replacement single phase motor will just do one job - the lathe - whereas a 3-phase inverter will power the lathe plus any other equipment you may buy (within the capacity of the inverter, of course). My inverter powers my milling machine, my ML8, my new surface grinder, and soon ( I hope) my graduate. When I acquire another 3-phase motor I shall change the motor on my old Myford ML4 metal lathe as well. I don't need to change any parameters - I just plug in a different motor and it works.

If you decide to buy a single phase motor, you could probably sell the 3-phase one on this forum to recover some costs - I'm sure there would be plenty of interest. (Or ebay, of course) but carriage could be more that the cost of the motor. However - personal opinion - I would definitely go 3-phase.

K


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## graduate_owner (27 May 2013)

Continuing previous posting,
I forgot to add that 3-phase also gives you a reversing facility. If you use this on your lathe, be careful because the work can unscrew from the mandrel when the lathe turns in reverse. I did this once and my 3-jaw chuck unthreaded itself and spun off around the workshop - really scary. I'm much more careful now.

K


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## Rick2058 (31 May 2013)

Thanks to you all for your comments and i will stay with the 3 phase.

Rick


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## katellwood (1 Jun 2013)

Naxie":3p0035bp said:


> 3 phase every time, best thing I ever did to my lathe!
> 
> If you look here https://www.ukworkshop.co.uk/forums/union-graduate-t66355.html you can read a thread on which I posted my experience on the company I got my inverter kit from.
> 
> ...




Hi Ed

could you post the photo's here of the tac

thanks


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