Help with a boxford motor

[jimbo84]

My Boxford CSB came with this unplated motor when I got it. the lathe turns freely by hand so it isn't seized.

It's capacitor start and run. It runs up to speed and the centrifugal switch can be heard kicking in but it seems woefully underpowered for its size and the lathe.

The motor measures roughly 150mm in diameter and about 200mm long and is a fair weight.

I've clamped it whilst running at speed not under load and it pulls 2.6a suggesting it is 0.8 horsepower which isn't a common size.

Should the lathe have a bigger motor?

 

[brightspark]

3/4 hp or 1 hp be ok a super 7 myford is fitted with a 3/4 hp

 

[Dcal]

Yes.
1.5hp is about right for a Boxford

 

[Guineafowl]

Boxford CSB Lathe

Power-feed apron as used on Boxford Model A, Model B and VSL lathes

www.lathes.co.uk

Apparently a 1/3 hp motor was fitted as standard.

 

[Dcal]

A 1/3 hp motor will work but it was sized at a time where HSS tooling was the norm.
The issue will be with carbide tooling where you need to take a deeper cut.

 

[jimbo84]

I had seen that a 1/3 motor was fitted to the original machines but a bigger motor was required to run them at the higher speeds. I don't think a 1/3 HP motor would even be able to start the lathe turning, with the amount this motor seems to struggle.

The reason I've been asking about the motor is that the large pulley was broken when I got it and has had a bad repair done with JB weld or similar and hasn't been set square onto the shaft so wobbled around a lot. In trying to dismantle the counter shaft to see if I could do anything with the originally damaged pulley I damaged the step pulley too . I'm now weighing up options wether to try and get replacement pulleys or just get a large motor with VFD to run it direct without the counter shaft.

 

[Dcal]

Bigger motor and vfd is definitely the way to go

 

[Seadog]

I have a 1hp motor fitted, with VFD. I did away with the counter shaft. I rarely experience any need to move the belt or engage backgear.

 

[jimbo84]

I would suggest a 3 phase motor and VFD every time - but not without careful consideration of the ‘gearing‘. Power decreases - even if torque is maintained - at lower motor speeds. The motor may not be as efficient when wide of its specified design speed. Cooling will be reduced considerably as the fan (motor) speed reduces.

I hadn't thought/wasn't aware of that.

It might be better going for a 6 or 8 pole motor then do you think to reduce the speed rather than a 4 pole and running it slower via the VFD?

 

[Newlands]

I have never had a motor overheat when tun at slow speed via a vfd. In practice, unless you’re running the machine all day long it isn’t an issue. How many times do you need to run at slow speed? On my mill it’s only when I want to tap a hole, which takes literally seconds. Same on the lathe. If I want to do some screw cutting I’ll select a lower speed using the gear box, and on the Boxford I used to own it was a matter of seconds to swop the belt to another pulley. It is a complete non-issue.
ps On my old Boxford I swapped the original motor for a 1 hp. I had a similar speed problem to you, caused by the previous owner using thick grease on everything. The spindle besrings were full of old dried up grease. After stripping and cleaning everything it ran like a sewing machine.

 

[Newlands]

But I didn’t make a sweeping statement. Nor did I say it was a cumulative problem. I specifically said ‘unless you’re running a machine all day’. And I also said that if you’re doing a job which might take longer then you can change gear rather than drop the frequency. I reckon you could count the number of motors burnt out by running a vfd on too low a frequency amongst the forum members here you could count them on the fingers of zero hands.

 

[6ply]

Measuring the current when the motor isn't doing much work will give a very poor indication of the rated output.

I used to have a Boxford (and still have a Denford Viceroy, which is similar in size) and 0.55kW (3/4hp) is just fine. If you want to change to a 3 phase + VFD I have some good used motors I'd be willing to sell. I also have a nearly new 8 pole motor that runs at about 680 RPM at 50hz. Personally, I'd stick with a 4 pole motor and countershaft. If you are in the Dorset area you could come take a look.

 

[jimbo84]

Measuring the current when the motor isn't doing much work will give a very poor indication of the rated output.

I used to have a Boxford (and still have a Denford Viceroy, which is similar in size) and 0.55kW (3/4hp) is just fine. If you want to change to a 3 phase + VFD I have some good used motors I'd be willing to sell. I also have a nearly new 8 pole motor that runs at about 680 RPM at 50hz. Personally, I'd stick with a 4 pole motor and countershaft. If you are in the Dorset area you could come take a look.

Very nice offer, unfortunately I'm a very long way away from Dorset.