Myford MG12 Grinder

Toms Wheels · May 3, 2012

The MG12 grinder I have is the old version 10" model. The manual with it is for the new 12" model. Nowhere can I find the old manual, it is the wiring diagram that is needed most.
Anyone here have a copy? $$ for your efforts of course.

Toms Wheels · May 10, 2012

Thanks to John Fisher for the copies that I needed.

Kiwi_007 · May 18, 2012

I also have an earlier 10" model with no manual, am I able to get a copy as well, would also appreciate a copy of the latter manual as I picked up a mint late mode swivelling workhead that I wish to use. The attachement to the table on the latter model is quite different to the earlier fixed one.....Thanks Kiwi

Toms Wheels · May 20, 2012

Kiwi, I purchased the late model manual from a guy in the UK. I found his website and PP the $$ to him, cheap with postage to USA was $23, most guys sell for $100. It is a very good photocopy, The 10" infomation was from a member here "lost in LA" John Fisher who also makes some very nice edge finders and tapping guides. He has a hydraulic model with a 400 page book, what I needed he just faxed to me, as it was diagrams and part lists.

Since the 10" models have not been made in 40 years, and Myford now gone, for new parts we are screwed. The USA distributor is selling stuff on ebay for the old dogs, but some stuff is stupid $$$ $800 for a wheel hub, $900 for a wheel balancer, along with switches, contacts etc.

Mark McGrath · May 20, 2012

Toms Wheels said:
Since the 10" models have not been made in 40 years, and Myford now gone, for new parts we are screwed. The USA distributor is selling stuff on ebay for the old dogs, but some stuff is stupid $$$ $800 for a wheel hub, $900 for a wheel balancer, along with switches, contacts etc.

A company in the UK bought the grinder rights from the receiver and were advertising all over the place.They were advertising on Practical Machinist in the form of posts to threads and Milacron barred them.
I have no idea what they are like but was not overly impressed with how they conducted themselves on here.

Toms Wheels · May 20, 2012

There is a UK company Jubilee I believe is the name. THey have the parts from the sale and are selling those. They rebuild and sell all grinders as their business. But the 10" units went out of production in 1972, the 12" units replaced them at that time. I have not read the anyone intends to continue manufacting the Myford units.

Go down to the the Chevy dealer, and ask for a wiring diagram for a 1961 Oldsmobile. Yeah Right!!

rgerlach · Apr 11, 2018

Does the 12" manual have a complete wiring diagram? I just picked up a 12" and I think it is configured 440V. The big transformer primary is connected to the 440V post and the contactors do not pull all the way in. I can press each motor contactor in and the motors will spin up but they do not seem to spin up as quickly as I expected. If I am correct I am hoping that it will just require changing the transformer connection to the 220V post and rewiring the two AC motors for 220V.

Ron G
Tustin, Ca

Toms Wheels · Apr 13, 2018

Step carefully in there. That transformer has a bunch of taps for sure. I would suggest removing and checking the coil voltage of one of the contactors, On my machine they were all 220V, and powered by the line voltage. The wheel motor was direct wired, no transformer in that line. The Workhead motor is driven by the transformer, and on most machines is DC not AC. Check the motorplate to be sure. Since you have the transformer, I would guess workhead is DC. AS the AC units have a VFD. If you have a dial switch next to the power cord connection of the Workhead, you have DC workhead. That switch is a reversing switch, for Internal/external grinding.

Note that I have the older model so your model may not be similar. Check those contactor coils first if 440 you will need to install a 220 to 440 transformer at the head of that circuit. Also you will need to adjust the overloads for the wheel motor, mine are adjustable anyway, half the voltage need twice the amps.

Richard King · Apr 13, 2018

I saw this ...top right paper "larger size" says electrical diagram.
http://www.industrialmanuals.com/myford-mg12-cylindrical-grinding-owners-manual-1965-p-4604.php

rgerlach · Apr 24, 2018

Toms Wheels said:
Step carefully in there. That transformer has a bunch of taps for sure. I would suggest removing and checking the coil voltage of one of the contactors, On my machine they were all 220V, and powered by the line voltage. The wheel motor was direct wired, no transformer in that line. The Workhead motor is driven by the transformer, and on most machines is DC not AC. Check the motorplate to be sure. Since you have the transformer, I would guess workhead is DC. AS the AC units have a VFD. If you have a dial switch next to the power cord connection of the Workhead, you have DC workhead. That switch is a reversing switch, for Internal/external grinding.

Note that I have the older model so your model may not be similar. Check those contactor coils first if 440 you will need to install a 220 to 440 transformer at the head of that circuit. Also you will need to adjust the overloads for the wheel motor, mine are adjustable anyway, half the voltage need twice the amps.

Mission accomplished. Mine had a large transformer that fed all the contactors and the DC motor rectifiers. It had 220V and 440V primary taps so I just moved the connection from the 440V tap to the 220V tap and all the contactors as well as the workhead motor functioned properly. I then went into the ID and OD motor wiring boxes. The ID motor was very straightforward. It was a Leroy and had a wiring diagram on a paper within the box. The Brown-Boveri OD motor was a different story. It also had a piece of paper with instructions but they were confusing at best and did not match the wires. I took a stab at what I thought was the correct change and it did not like it. I made myself a diagram based on the 440V connections and info gleaned from my ohm meter on the various wires. With this I moved the wires around and bingo the motor quickly came up to speed.

Thanks for your feedback.

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