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Swapping motor on DSG 1307 lathe.

crtten

Plastic
Joined
May 10, 2017
I have a DSG 1307 lathe, mid 1970 era. It is currently running on 3 phase via a rotary phase converter.

I would like to swap the motor out for a single phase motor. I looked over the wiring schematic and it looks like the main motor and the coolant pump are both 3 phase, and then a transformer steps down the voltage using 2 legs of the 3 phase to power the controls, lights, etc.

Does anyone have experience swapping out a three phase motor for single phase on a DSG 1307? I’m assuming it is a matter of swapping the main motor, coolant pump motor and substituting in a transformer for the lights/controls, but would like to hear from anyone else that has done this.

Thank you.
 

M. Moore

Titanium
Joined
Jun 8, 2007
Location
Vancouver Island, B.C. Canada
I have a DSG that runs on three phase power. I have never changed a 3 phase for a single phase on any of my machines. If yours runs fine with a rotary 3 phase generator why change out the motors? I ran my former workshop on a rotary with at least ten machines including my compressor and it all worked very well.

There is more to changing it over to single phase than just changing the motors. The electrical controls will not be set up for the single phase voltage so those will have to be changed or swapped out which adds to the cost. Also you cannot plug a single phase motor, that is to reverse it at full rpm without braking.

If you set up your rotary so that it is easy to turn on and off so that it doesn’t take any extra time or thought then I can’t see the problem?

If there is a problem then please elaborate.
 

crtten

Plastic
Joined
May 10, 2017
It works fine in the rotary phase converter, I just find it annoying to add an extra step to using my lathe.
 

M. Moore

Titanium
Joined
Jun 8, 2007
Location
Vancouver Island, B.C. Canada
You will find it more annoying to try and swap this machine over to single phase.

I definitely feel your pain as I go to great lengths to make my shop what I call “invisible”. It is the point where your shop just becomes an extension of yourself, where you don't have to think about anything but the work.
No extension cords to plug in or adjustment tools to find etc etc.

That is why I made the comment I made above, if the switch for your rotary is right above or near the lathe switch then it becomes easy and painless to turn it on and off. I have to turn on the 575 volt transformer each time I want to use my 13/40 Dean as I only have 120/208 three phase coming into my shop.
 

Bill D

Diamond
Joined
Apr 1, 2004
Location
Modesto, CA USA
A VFD will be cheaper and give dynamic braking, etc. You will be able to reuse you switches for low voltage controlling the vfd. I did this on my Harrison m300.
I added a pushbutton off switch that controls an old reversing relay. This allows me to shut down the VFD, and its cooling fan, when done for the day. I put the switch down on the front of the cabinet under the headstock out of the way.
Bill D

Drilling the 22mm hole to mount the switch was the hardest part.
 

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beckerkumm

Hot Rolled
Joined
Aug 5, 2014
Location
Wisconsin Rapids WI
I like a vfd for braking and filling in the gaps between the various speeds but if the lathe runs well and you don't need those upgrades, just keep the RPC. Swapping to single phase is a lot of work to make a machine worse than original. Dave
 

crtten

Plastic
Joined
May 10, 2017
How many hp is an M300? My DSG is 10 hp.

A VFD will be cheaper and give dynamic braking, etc. You will be able to reuse you switches for low voltage controlling the vfd. I did this on my Harrison m300.
I added a pushbutton off switch that controls an old reversing relay. This allows me to shut down the VFD, and its cooling fan, when done for the day. I put the switch down on the front of the cabinet under the headstock out of the way.
Bill D

Drilling the 22mm hole to mount the switch was the hardest part.
 

Bill D

Diamond
Joined
Apr 1, 2004
Location
Modesto, CA USA
M300 is 3 HP. I bought it running off a remote one Hp vfd. Seemed like enough power coming from a 9" South bend flat belt drive. Switched over to a internal mounted 3hp VFD.
A ten Hp vfd is under $200 for a no nanme Huan Yang on ebay. Would five hp be enough. With a vfd it does not have to be equal to the motor HP. but the motor can not deliver more power then the vfd is rated for.
Bill D.
 
Last edited:

woodsrider845

Hot Rolled
Joined
Dec 12, 2012
Location
ny usa
Hey guys, I have this great machine, that works great, but I really feel the need to fuck it up. I don't know why, but i feel like a large machine tool should just be ruined, and cause problems and wasted time.

Should I just be me, and ruin a great machine, or just stop being an asshole because I have to take a whole fucking extra step before I can use my lathe? Obviously I'm bored.

Bro, I'm selling clues. 3 for the price of 2. That'll save you money, seeing as you need so many.


But hey, do you.
 

Overland

Cast Iron
Joined
Nov 19, 2017
I'm running a Harrison M540 (21" x 80") lathe, 15 hp, with a VFD originally sized for 7.5 hp motor.
I just have to watch the cuts I'm taking, and therefore the amps, to stay within the capacity of the VFD.
When I get round to it I'll connect the lathe to my new 20 hp RPC, but until then, it'll be fine.
 

Overland

Cast Iron
Joined
Nov 19, 2017
Woodsrider....
Such a wonderfully helpful, constructive comment, you jerk !
Not everybody has your wealth of knowledge, of course.
The OP was just trying to learn !
 

thermite

Diamond
It works fine in the rotary phase converter, I just find it annoying to add an extra step to using my lathe.

You'll find it far MORE more "annoying" to replace the start switch and capacitors on a single phase motor every few years.

They do fully-braked to a dead stop reversing cumbersomely, if AT All, are not fond of constant starting from a dead stop, and get raggedy-ass under loads above about 70% or so of "nameplate". Right out of the box, you'd need a BIGGER 1-P motor to to as good a job as a 3-P and it won't EVER be "quite" as good.

It runs off an RPC?

Best leave it that way.
 

crtten

Plastic
Joined
May 10, 2017
So I guess the better question would have been, “why is this a bad idea?” I was not aware of the short comings of single phase motors compared to their 3 phase brothers.
 

M. Moore

Titanium
Joined
Jun 8, 2007
Location
Vancouver Island, B.C. Canada
Everyone who has responded has told you why it is a bad idea. It seems you are intent on finding a way for it to be a good idea.
It appears you bought this lathe in 2017 and loaded it with the advice of PM members. How did that go?
So five years later you want to change the motor? Why? If you have no expertise in re-wiring machine tools and do not understand what we are saying about changing the electrics on a machine of this kind then you are going to put a very large dent in your wallet not to mention the time involved and in the end you will have a machine that does not function as intended.
 








 
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