BAZMAK-Diary of a Myford ML7 lathe restoration

[ozzyjoe]

Lathe has arrived and i have done a part strip down to give it a good cleanup
2003 model with very little work,excerlent paintwork with a few chips to remedy
Next job is to make a stand and fit before reassembling.Its a heavy beast
First impressions very good.It has a 3 phase motor so i can fit a vfd or a new single phase motor
I may go with the latter to start so as to get it running soonerView attachment 117469View attachment 117467View attachment 117468

it must be a good drop, you are already a day older than us......According to your camera date!!!

 

[ozzyjoe]

Lathe has arrived and i have done a part strip down to give it a good cleanup
2003 model with very little work


She is a beauty......I am in love...…..you know that Will of yours? can we talk about it????? please install a vfd and keep the original motor on, with a good brand vfd you will have a very smooth control of the revs. Please don't sell this new baby .

 

[bazmak]

where in Australia can i get a vfd. I want a small box for controls every thing i see
is large multiple control box units with cables everywhere as in your photos
I will go for it if i can a a simple to wire compact control unit

 

[goldstar31]

where in Australia can i get a vfd. I want a small box for controls every thing i see
is large multiple control box units with cables everywhere as in your photos
I will go for it if i can a a simple to wire compact control unit

I believe that you had a 'Yorkshire' connection so I would mention that a unit weighs less than a pound.
Howverm years ago I bought a unit suit suitable for a myford and added a three phase motor-- and it doesn't work now.
Importantly, a year or two back I took it( the unit) to a Model Engineering Show to see whether the single exhibitor of such things would either comment or repair it. Frankly, I got the 'Bum's Rush' and was simply offered a new one.

Recently, I bought a Super7B with PXF but found that the wiring caused shorts. I was helped here- thanks Baron J, but it ended up being repaired locally with new wiring harness etc for the low price of £60 or £70.

So, I don't know but a new vfd will be easy and light to post and not incur British taxes. If that is the way that you want to go.
ME???????- well let's say politely, I have. a spare single phase motor-- which works.

Best of Luck

Norm

 

[deverett]

Following on from Norm's posting, 2 well known suppliers of vfds in the UK are

Newton Tesla (which I have used and am completely happy with)
https://www.newton-tesla.co.uk/product-category/lathe-speed-controls/and
Transwave Transwave Converters

There are 350 vfds for sale on eBay UK at the moment.
No doubt there are other suppliers from other parts of the world.

Dave
The Emerald Isle

 

[jack620]

where in Australia can i get a vfd.

This is where I got mine:
0.75kw/1HP 240V Single Phase Variable Frequency Compact Drive Inverter VSD VFD

They can be operated from the built in control panel, but it's much more convenient to use remote switches. The remote switches will be much more robust and the VFD can be enclosed in a box where it will be safe from metal chips, coolant, damage to the wiring, etc.

 

[ozzyjoe]

where in Australia can i get a vfd. I want a small box for controls every thing i see
is large multiple control box units with cables everywhere as in your photos
I will go for it if i can a a simple to wire compact control unit

Don't warry about all the boxes and wires in my photo,they are for looks only.
The VFD is the first box on the left , it is a company from the UK and they main depo for AU is here in Sydney.
1 Wire in and 1 wire out,start-stop ,forward -reverse, speed control all in one control panel.
If you want a cheaper version (made in china)there is a local eBay reseller that has some for a good price at the moment, but I have to buy one and test it before recommending it to you.

 

[ozzyjoe]

My first speed control box, it was more than $150 for parts back then,now you can buy a vfd for $98 on eBay.

 

[bazmak]

Well the VFD arrived today.Just a cheap chinese one,just to get me started
I mounted it to the side of the cabinet for now and had a quick play. I was under
the misconception that the digital readout was for the rpm but now i realise
its only the frequency. I really need to get a rev counter at some stage
With the motor drive on low range and the spindle belt in the middle i got
a speed range of 0 to ave,but when i moved the motor pulley to high range
it did not seem to have the desired effect and could not get a faster speed
When it was wired direct to the motor at first it was very quiet and smooth
but did not seem to drive the motor at top speed ie 1425 ish Any advice
Attached are photos of the original wiring.Question,can i use the 3ph stop/start
box and wire it to the n1ph supply before the vfd

 

[Charles Lamont]

I am not an electrician, but I think the answer is no. Those appear to be momentary push buttons. They would be used with a contactor (and overload relay). The contactor would be wired to be self latching in the on state.

AFAIK The VFD just needs a normal mains plug. Any external controls would be wired to the (24V) control terminals in the VFD.

You could use your button box for that, but you may well still need a small relay to latch the on state. VFD remote control boxes often have more functionality than that, with a speed control knob, probably reverse, and perhaps a jog function too.

I have a control box for my S7 as a back-burner project, but it is coming on; the metalwork is in the 'paint shop'.

 

[cds4byu]

There are probably two ways you can use your start-stop switches.

The first (and the one I used on my conversion) is to leave the switch connected to the contactors that started and stopped the motor when it was not in variable speed mode, and then use those contactors to switch the control wiring on the VFD.

The second is to program the VFD so that instead of having the control wiring be a Run/Don't Run input, it will have a Start input and a Stop input. I'd be happy to look at your manual to see if I can help you figure out how to do the programming if you'd like.

Carl

 

[jack620]

can i use the 3ph stop/start box and wire it to the n1ph supply before the vfd

No. As Charles said, they are momentary switches. Use them to send start and stop commands to the VFD. You don't need a contactor to switch the single phase input to the VFD. Just switch it on and off at the power point. And you are going to want a remote potentiometer for speed control. They are usually 5K linear. The one on the VFD will be quite flimsy and if you break it you may lose the ability to program the VFD.

Nice looking lathe BTW.

 

[bazmak]

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

 

[BaronJ]

Hi Barry,

Are you sure that the motor is wired in delta ? The low power suggests that it isn't.

 

[bazmak]

Hi Baron,as i say has very limited electrical knowledge. I did not touch the motor conns just used the existing wiring/cable
to connect direct direct to the VFD.Attached a couple of photos.Whats involved delta wiring ??

 

[BaronJ]

Hi Barry,

Hi Baron,as i say has very limited electrical knowledge. I did not touch the motor conns just used the existing wiring/cable
to connect direct direct to the VFD.Attached a couple of photos.Whats involved delta wiring ??

View attachment 117955

If you look at the rating plate, fourth line down. It reads, translating the symbols, V=voltage, star/delta, 380-415/220-240, 50Hz.
The lines below gives the current for star then delta connections.
Then below that the insulation class and working temperature.

The important lines for your purpose is the forth one. When the motor is wired in delta it is a 220-240 volt motor and the load current about 2.3 Amps three phase.

View attachment 117956

This bit is a bit harder ! Assuming that the motor wiring has not been altered from original, "U-V-W" are one end of the three winding's. "Z-TB1-TB2" should be the other ends.

The wires have to be swapped around in order to swap the winding's into delta. I'm struggling to remember which ones have to go where. But basically in star all three winding's will go to a common point. Those three wires have to be separated and the end of one connected to the start of the next winding in line.

These diagrams will help. I think that your motor is configured as the right hand diagram and it should be reconfigured as the left one.

 

[jack620]

This is where i struggle with very limited electrical knowledge

This is a job for someone who does have some electrical knowledge. Do you know anyone who can help you with this?

 

[Charles Lamont]

I think the black, brown & grey all being connected to Z may indicate that it is star wired. But in any case the plate also says it is 370W (1/2HP). That is not enough to drive a S7, even less so at reduced speed.

 

[BaronJ]

I think the black, brown & grey all being connected to Z may indicate that it is star wired. But in any case the plate also says it is 370W (1/2HP). That is not enough to drive a S7, even less so at reduced speed.

Hi Charles,
Forgive me if I disagree with you, my S7LB only has its original 1/2 HP single phase Brooks motor, and it has plenty of grunt. So far I've never found that it is under powered in any way.

 

[goldstar31]

Hi Charles,
Forgive me if I disagree with you, my S7LB only has its original 1/2 HP single phase Brooks motor, and it has plenty of grunt. So far I've never found that it is under powered in any way.

I'm with John here. I have just sold a sight glass Myford Super7B and replaced it with a 'recent' Sup er 7B with PXF- both with 1/2HP motors. The latter had a split phase motor and John was very help i trying to fathom its peculiarities.

I can go back- Oh till the end of the last war and getting a bit done for a Henwood athodyd jet engine being a precocious school boy. The bit was done on an early ML1or up to 3( long time ago) and it was powered by a quarter horse ex- washing machine motor.

When I got around to having a Roo¨nd bed Drummond and then a Pools 'Major', they. were also powered with ex washing machine motors.
The ONLY bigger power was the 'line shafted' ML7 whch had- a full 1 HP and one 1/3 HP running as he. changed his working.

always wanted a Bormilathe or a Murad Antarctic lathe. Oh, yes a Holzapfell but that's another story.