Boxford needs new motor.

I have an old boxford CUD lathe and the motor is getting very tired.

It's a single phase but I'm considering going 3 phase, possibly in 240v as the VFDs seem to be a bit cheaper.

My main questions are, what mounting plate size am I looking for?

How many horsepower can it handle?

I'm eventually hoping to put a larger chuck on this one to beef it up a bit as I use it for work. I've read somewhere that these machines are more than capable of handling a bit more speed and power.

Any advice welcome, regarding the VFD set-up as well, if anyone's been through this transition. Thanks in advance.

If it's any help, I re-motored my ME10 with a 0.75kW motor and 0.75kW Teco VFD. the motor was physically the largest size I could fit without too much surgery of the mounting arrangements. Underdrive is probably different. Control of the VFD is via a remote pendant on the lathe stand. I've set the VFD to give a top speed of ~1900rpm, against the original of 1300rpm. I'm sure it would go higher. No probs. so far, though my useage is hobby only.

All components, inc. switches and wiring purchased from "Inverter Drive Supermarket", who give all dimensions, instructions etc on their website.

Total cost was <£250. Money well spent IMO.

Edited By Clive Brown 1 on 04/06/2020 08:46:32

Edited By Clive Brown 1 on 04/06/2020 08:47:48

I believe motor mounts are standardised, the problem is the bigger the motor the bigger the mount so 1hp will swap with 1hp otherwise you will need to make an adapter. Universal motors will mount on the end or any one of the 3 sides. If you intend to only use the VFD for speed control you will need more hp or low speed power will be down compared to switching pullies.

IE2 rated motors are much more efficient than old stuff, I have a 1hp that has the same plate current as a 1980's 1/2hp Brooke.

I believe mine is 3/4hp and I've never felt like I need more power. This is the original Brooks Crompton 3 phase.

I also got everything I needed from "inverter drive supermarket". Seems like a good company to deal with. I went with an invertek drive. Made in Wales! Which is nice to know should I need help.

Thanks for the great info. I do already have a couple of motors in mind, both 1hp, the first being a dual voltage.

https://www.ebay.co.uk/itm/192580042652

https://www.ebay.co.uk/itm/142185182520

I was planning on looking at the Bangood website for a VFD but will check out the inverter drive supermarket first.

The original motor says it is 0.75hp, which seems a little strange to me as I thought these had a half hp motor as standard and the motor definitely looks standard. Wiring everything up isn't too much of an issues as my brother used to be an electrician with plenty of 3 phase experience under his belt.

Edited By Ian Rees 1 on 04/06/2020 11:07:17

I've replaced the motor several Boxfords over recent years. I think you may find it a struggle to get the motors you've linked to, to physically fit, due to the big box containing the capacitors on the side of the motor. You may also need to modify the mount on the motor and/or the lathe itself. If you can source a B56 frame foot mount motor (ideally resilient mount) it will drop straight in without modification.

Edited By Gavlar on 04/06/2020 11:41:22

In my Boxford days with VFD I found that a 1.1kW 6pole motor with a 60mm V belt taper lock on motor and the existing one (ca 90mm) on spindle would do anything in cooperation with a HuanYang 2,2 kW inverter.

I only used back gear for spindle locking while changing of chucks.When I forgot to release, (more than once) motor would turn and belt slip.The combination enabled a 3mm wide parting of tip on 100 mm mild steel.

Wow, the price rockets up when I start looking at B56 mount motors. I can see this is going to take a bit more research. Thanks for the information.

I found a picture of my Boxford when space was not a problem

1.1kW six pole

A 3 phase motor won't have the start or run capacitors found on a single phase motor.

I've looked at measurements of these modern motors and it seems that the ones that are cage size 80 will fit, physically, whether I'll struggle with space to line up shafts and pulleys is yet to be discovered. There aren't many 1.1kw, 4 pole motors in that category (I need 4 pole if I want to match the specs of the old motor).

I did some searching on the mounting hole dimensions of the old B56 frame and from what I can tell, my old motor doesn't match those measurements. I think the logical next step will be to remove the old motor and mounting plate so I can measure it more accurately and see if I can get a B3 foot mount, 80 cage motor in there.

I'm more prepared to spend time getting a modern, cheaper motor to fit than to spend twice the price on a B56 motor that might not even fit.

A 0.75Kw 80 frame B3 foot 4 pole motor from The inverter drive supermarket is recommended or the same size is available in the next power range at higher cost.

**LINK**

I bought one of these to power a 0.75Kw motor from the same people and took advantage of their quick start guide which makes all of the wiring and programming easy. You won't ever need to be one of the people trying to get help on forums when the instructions turn out to be incomprehensible.

**LINK**

That's actually cheaper than the eBay one I was looking at, although postage may up the price a bit. I wonder if they offer any kind of mounting plate? Maybe I'll fire off an email to them.

The I D S prices do not include VAT or postage, but the quick start guide is well worth the extra. The instructions which come with VFD's are fine for electrical engineers but pretty much mumbo jumbo to everyone else. So many people just go out and buy the cheapest and then whine about not being able to get the stuff to work.

Your present motor is on a mounting plate, whats wrong with that? If it cannot be modified, then you will have to make one.

Edited By old mart on 05/06/2020 15:59:39

I emailed the inverter drive supermarket and the guy called me back almost instantly. We chatted for quite some time, he didn't mind wasting his time with me, a very nice bloke.

It seems there are already sliding plate adaptors for this job, which he emailed me the spec sheet for. What I need to do now is remove the old motor and take measurements, then get back to him and he'll sort me out with the motor and plate that I need. I may even be able to get a larger cage motor in there, if I fancy going up to 1.5hp.

He also explained to me that you don't lose power in the lower rev range, only when you go higher than the specified speed of the motor do you lose a bit of power.

I have to be careful where I mount the VFD, it's susceptible to dust, swarf, damp etc. I'll also have to figure out what I want in the way of switching but that will all come when I've sorted the motor.

All in all, a fruitful conversation, can't recommend that company enough.

My VSL has a 1 1/2 hp motor. Originally had a Siemens inverter but it died quite quickly. Now have a Jaguar cub with pendant, which is excellent. Very powerful but the belt slips on large drill use. Anyone know how long the lunk belt for a 500 vsl should be?

That link I posted for the 1hp motor had a set of expected power outputs at different frequencies, and the figures don't match the advice given to you by the I D S guy. This is the box I put the VFD for the mill in, it is ventilated top and bottom and gives plenty of protection. A similar setup could be used with a lathe.

Looking at the illustration in the lathes UK website, your three door stand may have room above the motor for the VFD, or in the middle if the coolant is not used. If you buy from the I D S, make sure whichever VFD you get includes their quick start guide. You can download and print the pdf to have a good read first.

When I had a Myford ML7, I was told that if converted from single phase to three phase, the 3/4 single phase motor should be replaced by a 1/2 hp three phase. The reason given was that the three phase motor would run more smoothly, (Presumably like a six cylinder engine compared to a four )

Presumably, you will be looking to replace the original motor witha four pole, so that it still runs at 1470 rpm (or thereabouts ) to give the same speeds, nominally as before.

But with a VFD, you can increase the frequency beyond 50Hz (European sites ) and so obtain higher motor speeds if you need them.

Howard