Lathe problems

[Krawl]

I have craftex CT089 lathe, 13 x 24 I believe, anyway last night I was working away and I stopped to take a measurement and then when I went to start again it would not start. I could hear it laboring but it would not turn, it would however start in reverse. So I took the belt off to unload the motor it runs fine in reverse but it will not run forward, if I start it by spinning the pulley on the motor it will turn slow but it will not come up to speed. Any ideas?

[mixdenny]

I have no experience with that particular machine. But in general, those are symptoms that the starting capacitor has failed (unlikely since it still runs in reverse), or the centrifugal switch contacts have stuck and it is on the run windings instead of the start windings. I'm not sure why it will run in reverse, but my shoptask growls like this every now and then, and it will also run in reverse, which clears the problem, so I am assuming stuck contacts. On my motors, the contacts are under the removable end bell of the motor. If you can get to yours, see if they are stuck together, just gently pry them apart and clean them a bit with a very fine file.

Dennis

[Krawl]

Yeah I was thinking the starting cap as well, mine hase too caps on it so would one be reverse and the other on forward? I'll switch them and try and I'll aslo check the contacts, thanks for you input.

Kevin

[Bubba]

Kevin,
With two caps, it sounds like it also has a run cap. The two are probably different values so DON'T interchange them. The start cap is used for both directions. The forward reverse is handled in the switch by changing the ends of the start winding.

[mixdenny]

As Bubba has posted, one cap is the starting cap and the other is the run cap, and they are different. If you suspect them, they can be checked if you know anyone with a capacitor checker. Grainger sells replacements that are rated for more starts per hour than the original cheap caps that come on most import motors.

Another thought, since it runs in reverse, is that the switch has a problem. I would check the contacts. Like I posted earlier, mine will occasionally growl and run slow in forward, but if I start it in reverse it has cleared the problem everytime so far. I can't explain why it would start in one direction and not the other.

Dennis

[KOS]

i had a similar issue with my 11x26 lathe. In the end I replaced my start and run capacitor as well as my switch. Although I beleive it was the run capacitor that was my original problem. I just figured while i was at all of this I would just upgrade everything in there.

[handlewanker]

Hi All, one thing a lot of people don't know is that single phase motors, (as are fitted to the majority of the cheaper home type lathes) are not designed to be stopped and started more than a few times per hour.

This is not a problem with 3 phase maotors.

The fact that the manufacturers fit single phase motors with on/off switches for stopping and starting is because it's too expensive to fit a clutch in the drive mechanism which allows the motor to keep running.

Every time you hit the start switch the start windings are engaged, and as they are only designed to start the motor and bring it to synchronous speed and then drop out without burning out, it doesn't take much imagination to realise that after a few starts the windings get hot.
Most, but not all, single phase motors are designed to run continuously, but this doesn't mean they can be stopped and started frequently.

I overcame this problem by fitting the electric clutch from a cars airconditioner pump to my Colchester Bantam lathe, and this allows me to keep the motor running continuously and stop and start as many times as I want for measuring purposes.

The clutch is powered by a 12 volt transformer with rectifier for DC, and only requires about 2 amps to power it.
I've also fitted an electric clutch to my 1-1/4" capstan lathe and this usually runs for 6 or 7 hours at a time.
The motor on this lathe is a 3HP 3000 rpm single phase induction motor.

The electric clutch will handle quite a few horsepower and at high speeds as well without a problem.

Most car wrecking yards throw the aircon pumps away as scrap because they're too expensive to repair when they fail, but the electric clutch on the pumpshaft end is usually still good, and the whole assembly can be had for a few dollars, just don't say why you want it or the price goes up.
Ian.

[tonyidle]

Hi Ian

This is my first post: I was Googling "electric clutches" because I had an idea that I could fit one to my Bantam and I found you had already done it!! My concerns were price (of course) and whether a cheap (aircon) clutch would handle the torque. I think your post answers both questions. Would you be willing to share details (and maybe a picture)?

Regards

Tony (in Cumbria, UK)

[handlewanker]

Hi Tony, no problem.
I've got a few photos I took but need to be resized for the forum, but the fitting is straight forward and all it needs is to get the clutch as mentioned previously, discard the airconditioner part, or make it into a compressor, and go from there as the mounting could differ a bit from model to model.

I don't know what model Bantam you have but mine is the flat belt type dating from the 1930's and as it used power from a line shaft, it came as just a bare lathe, so I had to build a countershaft to carry the second step pulley and input reduction drive with motor mount etc.

Once you've had one fitted you'll never do without it.
I hope you are up on your engineering skills as there is a bit of fitting and turning to be done.
Ian.

[tonyidle]

Ian

Thanks for the quick response. Mine's a 1960s MkII Bantam - ex-school & appears to have been mothballed for some time before removal. I've only just installed it. My previous experience was with a Super 7 (with clutch of course) so I know I'll miss having one. Although the machines are so different & photos are unlikely to be of help in installing a clutch on mine it would be nice to see photos what you've done - if it isn't too much trouble.

I don't mind machining & fitting

Thanks again

Tony

[handlewanker]

Hi Tony, heres a couple of photos I already have. I'll take a few more so that you can see the mounting.
The mounting will differ from make to make but the principle is the same I think.

The pulley size is about 160mm in diam with a B section Vee belt.
Some of the air-con compressors have twin vee belt drives.

I think your lathe has the drive directly into the top of the headstock casting with the motor down near the floor.
Ian.

[tonyidle]

Ian - thanks again.

Mounting it shouldn't be too difficult on mine: the pulley on the headsock gearbox is under the changewheels cover & the shaft it drives protrudes around 3.5". The pulley itself is installed 'boss outwards' & hides the bearing cover. The bearing cover contains an oilseal & is a flange fit with 4 bolts so either a new bearing cover with mounts for the clutch stator/coil or an adaptor to fit the stator to the existing bearing cover will be easy options. The shaft protrusion will, I hope, be long enough to accept the driven & driving elements.

Whilst Googling electric clutches I've found them used on tractor PTO's and on the cutter drives of lawn tractors - all of similar size to the aircon pump clutch.

Yours looks to be a nice, handy, setup.

Regards

Tony