BAZMAK-Diary of a Myford ML7 lathe restoration

[Charles Lamont]

Interesting. My S7 came new from Reeves in 1973 with a 550W single phase motor. A contemporary brochure recommends 1/2 hp 3-phase or 3/4 hp single. Mine now has a VFD with a 750W motor. In top speed, at 50Hz, I can hear the speed drop when I start drilling, but then I do run it with the spindle bearings on the tight side. I would say anyone who regularly uses carbide tools (I don't) would be better off with the extra power.

 

[BaronJ]

Hi Charles, Guys,

I've heard this before, the same model lathe but fitted with different size motors.

I know a couple of people that have exactly the same lathe and both have different motors. One is a 3/4 HP Brooks and the other is 1/2 HP but a GE (I think) one. The Brooks ones have rubber anti vibration mountings, the GE one is rigid.

I think that Myford fitted whatever motor they had in stock at the time of manufacture.

 

[cds4byu]

This link shows how to change a Brooks motor from star to delta.

As I understand it, you will be running the motor at half voltage if you are running in star, so it's not surprising your power is low. Half the voltage gives 1/4 the power.

Hope this helps! Good luck.

Carl

 

[awake]

With regard to a 1/2 hp motor ... it does depend on which half of the horse you get. I have had experience with new, import, "1/2 hp" motors that apparently were assembled from just the fat and gristle of the horse, no muscles included. I also have some old "1/2 hp" motors that not only must be all muscle, but also seem to have used a bit more than half a horse - they seem more like 3/4 hp!

 

[BaronJ]

This link shows how to change a Brooks motor from star to delta.

As I understand it, you will be running the motor at half voltage if you are running in star, so it's not surprising your power is low. Half the voltage gives 1/4 the power.

Hope this helps! Good luck.

Carl

Hi Carl,
Thanks for that link, refreshes my memory. I'm fairly certain that the colours are correct for the motor Barry has. Brooks used several different connection boards in their motors but the wiring colours would be the things to go by. An ohmmeter would confirm it.

 

[bazmak]

Thanks guys. I have taken the motor and VFD to a local motor rewinders and he has said he can
rewire to delta and the conns have to be picked up inside the casing. Nice asian guy with heavy accent
when combined with mine made conversing difficult.However with additional sign language he
indicated that not enough uummff in star but ok in delta.Will have to wait and see

 

[BaronJ]

Hi Barry,

Now you have got it sorted. Once you have the VFD correctly set up it should be fine !

 

[bazmak]

Thanks Baron,your simple answer made sense.Just picked it up and refitted to the lathe
Seems to have sorted it all.More speed and torque.Bit more tidying up before testing
under load. First job is to make an M42.5x2 male spindle nose plug gauge so i can make
an adaptor plate to fit all my 4" range of chinese chucks. I have purchased an ER32 collet chuck
and full set of collets. I also have 3 and 4 chucks etc. Even though this super 7 can easily
swing the heavier 5" chuck i prefer a 4" for most work. As soon as i get set up i will
post a video

 

[BaronJ]

Hi Barry, Guys,

The Myford spindle nose isn't M42 by 2 mm,

This is the drawing for the spindle nose !

Note that its is 1.125 by 12 tpi Whitworth thread.

 

[bazmak]

Mine is a super 7+ or bigbore the nose is M42.5 x 2mm pitch with MT4

 

[BaronJ]

Mine is a super 7+ or bigbore the nose is M42.5 x 2mm pitch with MT4

Hi Barry,

I should have guessed ! I'd forgotten about the "Big Bore" version.
However I'm surprised that they have gone metric. Does that mean that nothing else fits ?

 

[bazmak]

Yes i have a 4" 3 jaw ,a 6" 4 jaw and a faceplate.Thats why i want to make an adaptor plate
to suit the chinese 4" range of chucks.I have bought an ER32 collet chuck and set of collets
i also have 3 &4 jaw s/c and 4 jaw independnad chucks.Should still be able to pass 1" thru
the headstock.Will post if its all successful.I usually do all the lathe work on my chinese lathe
and just the final skim/fitting on the Myford. (so i dont get too dirty). Again it is a metric lathe
with only the cross and top slides and the tailstock running on metric screws.The leadscrew and gearbox
are still imperial, but has a metric conversion kit to cut metric threads by changing the banjo assembly

 

[goldstar31]

RDG- the 'new' Myford has an adapter 'nose' for the Big Bore variety. Over £100 though in the UK.
As for the Chinese lathes- well, I listed what I did for the SiegC4 which I have. I also did a conversion kit to fit Myford bits and ER25 collets as well as Myford collets.
So I can fit a 'Myford' rotary head and the GHT small dividing head and the Myford vertical slide.
Jim Batchelor writing in GHT's Workshop Techniques added the Universal Pillar Tool modifications for those interested in clockmaking. I seem to recall Tom Walshaw writing as Tubal Cain doing Ornamental Turning on the Myfords.

Me? I've got the Potts grinding and drilling spindles. Merely saw what could be done. With a bit of 'engine-uity' the Quorn also fits.

Kind Regards

Norman

 

[JRSherbundy]

I am having problems with the VFD.I wired it to the motor and it worked ok allthough the speed seemed slow
When connected to the lathe in the low speed belt range it runs but no torque.I can stop the spindle with
my hand.In the high speed belt range it wont run at all.There is just no torque.A tight belt prevents it running
Any advise would be appreciated. I am concidering getting a new 1hp single phase motor and stick with
the belt drive.This is where i struggle with very limited electrical knowledge

Sorry for posting so late on this issue. I have been reading through these posts and I agree that the motor is probably wired for Wye (Star) Connection. This connection puts a lower voltage on each of the three windings, so each winding sees about 57% of the voltage it would see if connected Delta. Interestingly, the motor will run at or near full speed assuming the loads on the motor are low enough, meaning the belts are not too tight and not so much friction. This Wye connection is often used as a means of starting a motor and getting it up to full speed before reconnecting the windings as a delta connection (done through a sequence of mechanical switching of winding connections). When connected in Delta, the motor can operate a full power. This starting method was often used on large air compressors here in the USA for motors of 300HP to 500HP. The unloader valves on the compressor are open when in start mode thereby keeping the load on the motor down, and allowing it to come up to full speed. Then when at full speed, the winding are mechanically reconnected in Delta configuration and the compressor is off and running as desired. The advantage to this method of stating is keeping the starting current down to a lower more tolerable level. I have no idea why the previous lathe owner would want to run the motor Wye connected unless it was because of the voltage available. So getting back to the problem as noted, I agree with the comment that the motor was in Wye connection as as such had not ability to handle load. I did not see anything in the motor terminal box photographs which would suggest the previous owner used a Wye-Delta starter since all six leads of the motor would have to be brought out of the terminal box and connected to the starter. Those pictures showed the motor wiring was Wye connected for sure.

 

[ozzyjoe]

This Wye connection is often used as a means of starting a motor and getting it up to full speed before reconnecting the windings as a delta connection (done through a sequence of mechanical switching of winding connections). When connected in Delta, the motor can operate a full power.

Thanks for clearing this up, it all makes sense now.
Is there a circuit that we can build (via means of timers, relays and /or switches) to connect our motors, like the example you give above. I know it is cheaper and quicker to buy a single phase motor but i prefer to keep the original 1954 motor on the lathe. Keep in mind that we are also using reverse/forward switches in our motors.
Thank you.

 

[bazmak]

Well i am almost ready to make chips on the big bore.First job is to make an adaptor plate
Heres the progress so far. Bit long winded but i managed to use available materials Managed
to succssfully cut and a male and female M42.5 x 2mm thread.All done on the Chinese lathe
and ready to be finished off on the bigbore.Very pleased with the days work

 

[BaronJ]

Hi Barry,

Very nicely done

 

[bazmak]

I finally made chips by finish machining the adaptor plate in situ. Shame to get the lathe dirty
Its a beautiful machine so smooth and quiet. When i did a heavy cut it did bog down so for future ref
the 1/2hp motor and VFD may not be adequate.May fit new 1hp single phase later with f/rev switch
and keep both as options. The new adaptor plate works well and has given me a new range of chuck options

 

[goldstar31]

Barry
Congratulations. Most intersting.

Thinking of faceplates, I have one from a 9 x 20 which is almost too big. What I like is the smaller ML10 one- and its counterpart 4 jaw independent chuck.
I was wondering about whether you still have the Sieg SC4 as I wondered whether I could use a Sieg C4 SC chuck grafted onto a Myford catchplate( I have TWO). I have two sets of soft jaws for the Sieg which were heavily discounted.

Comments would be appreciated

Cheers


Norman

 

[bazmak]

Hi Norm, the 4" range of chinese chucks have a 72mm spigot and are the same as the ones
i have just fitted to the bigbore. They are also the ones that i fit to all the ML7s and super7s
The chinese chucks as fitted to the SC4 are good quality and cheap that is why i use them
as i dont always get decent chucks with the lathes i buy. I always use a spare threaded adaptor plate
or machine up a catchplate.That way i can economically resell an ML7 with say 2 new chucks
The answer to your question is yes you can machine a catchplate to fit your sc4 lathe chuck
I try to avoid having to screwcut internal/external threads,but as you can see i had to with
the bigbore. Saved having to buy one (very expensive) I also took the long route and used
available materials.Saved having to buy anything,being a tightarse Yorkshireman. From my past posts
you can see that my sieg chucks fit my Myfords and i made an adaptor to fit the Sieg that accepts
all myford chucks