Cowells lathe concerns, advice needed

[Gbitz]

Hi all,

This is my first post, but I have "lurked" here for a while and marvelled at the technical knowledge and understanding of the members - I really need some expert input on my little problem, and thought I would ask here.

I am extremely inexperienced in lathe (and, for that matter, all engineering matters) - so please be gentle on me ;-).

My hobby is messing around with watches, and I figured-out a little while ago that a lathe would be really useful for the watch modifications I've been doing - I saw an older Cowells lathe on eBay at reasonable money with only 40 minutes to go (I'd done a little research and found that Cowells made a solid, accurate little lathe - for which quite a few accessories are available) - I bid and won at a reasonable price, the lathe seems very nice and came with a milling slide and vice and a Jacobs chuck for the tailstock.

The lathe has a 3-jaw chuck - I knew I would also need a 4-jaw and a collet chuck but thought they would be easily available - here is where my difficulty comes in - it seems that the older Cowells lathes had a 14mm x 1.5mm thread to hold the chuck on, where newer Cowells have a 14mm x 1mm thread (the same as Unimat, I believe). Cowells themselves sell chucks only with the newer thread and there are plenty of aftermarket chucks with the 14mm x 1mm thread (probably because it also fits Unimat) - I have been able to find nothing (not even a backplate) with my lathes's 14mm x 1.5mm thread.

The tailstock also has an awkward MT0 taper in the tailstock which seems to make finding a live centre etc. to fit pretty difficult.

The Cowells seems like like a nice, solid, piece of equipment but the apparent restriction on the hardware it will fit makes me wonder if it will prove adaptable enough in the longer term.

Bearing in mind my current lack of experience in lathe work, Is there anything I can do to fit the available chucks to my lathe, or would I be better off to put the little Cowells back on eBay, and find something else which better suits my purpose. If so, any ideas what else would be suitable (I don't need to do super-tiny turning work, like a proper watchmaker - just turning movement rings, turning-down the shank of, say M2.5 bolts etc).

I would be very grateful for any advice  you can provide.

Many thanks,

Andy

[Jasonb]

You should be able to make a backplate yourself to mount a small 4 jaw chuck to.

The thread can be tapped as I doubt you will be able to screwcut it on the lathe. Its then just a case of carefully measuring the other hole sizes and registers from the 3 jaw and replicating these on the new backplate.

Once you have a bored & threaded hole in the backplate it can then be screwed onto the spindle nose and the face skimmed true and any register added for the new chuck. Drill & tap suitablethe mounting holes and screw the new chuck to the backplate.

Tracy Tools will have a M14x 1.5 tap at reasonable cost

http://www.tracytools.com/

Jason

Edit just looked at my old Cowells catalogue and you may well be able to cut the thread on teh lateh if you have the right changegears

[Swarfing]

Andy

Where abouts are you? i have an M14x1.5 tap to do the job. Thats the same size as some centre posts on QCTP, it is on mine

[andyf]

Hi Andy,

You might join the Yahoo Cowells 90 group http://groups.yahoo.com/group/cowells_90/ and seek advice there, but I think you will find that off-the-shelf 14x1.5mm chucks and backplates are unobtainable and that it is either a case of making your own as Jason says, or getting a new 14x1 spindle from Cowells. That won't be cheap - I reckon that weight for weight, Cowells must be one of the world's most expensive hobby machines.

Did you get a faceplate with the lathe? If so, you could bolt a chuck to that.

I have a Perris lathe, which became the Cowells in the late '60s or early 70's, and that has a 1/2" x 20 TPI spindle nose, so I'm in a similar position.

The Perris/Cowells tailstock has always been 0MT, as has the spindle. Cowells will sell you a revolving centre - there's one listed near the bottom here: http://www.cowells.com/pricelist.htm . See what I mean about the prices?

Other micro lathes you might consider are the Taig (sold in the UK as the Peatol) and the Sherline. If you want to go in for screwcutting, I don't think an accessory is available for the Taig/Peatol, but there is one for the Sherline, though you would be limited to imperial threads, and possibly close approximations of some metric ones.

Final suggestion: try a Wanted Ad at http://www.homeworkshop.org.uk/ for 14x1.5 chucks.

(another) Andy

[AR1911]

You can get MT0 centers from Sherline.
Caveat: There are two flavors of MT0, apparently.

As for 1/2-20 chucks, I have a 3-jaw I'm considering selling or trading.

Back to the OP, one thing you might consider is using a Helicoil or similar thread repair to change the thread on yours.
Find the kit for 14-1.5, which would be a tap, possibly an install tool, and a few inserts.
You would drill out the existing hole to fit the repair insert.  You would want to do this on a mill to ensure perpindicularity

[Jasonb]

Depending on what model the OP has some of the Cowells machines say they have a "Modified MT0" so a standard one may not fit.

Jason

[Gbitz]

Hi all,

I just wanted to thank you all very much for your helpful suggestions - there is a lot to think about, it looks like I've taken-on quite a project (rather than bought a machine to help with my watch projects  )

I am interested in the idea of using a tap to make the 14x1.5mm thread on a backplate - would I be able to do that on the Cowells itself? - I mean, would the little tailstock be able to hold a 14x1.5mm tap, or would I need to do do that on a larger machine?

Thank you all once again.

Best regards,

Andy

[Bogstandard]

Andy,

I would suggest to you NOT to use a tap for making a backplate thread, it just wouldn't be accurately placed square enough.

When cutting backplate threads, it needs to be cut, or majority cut, before feeding in a tap to clean up the thread, by single point threading.
You then stand a good chance of everything being square and running true.



Bogs

[Shadow]

I have a Unimat SL, Unimat 3, and Clisby, a couple of 6" Atlas and I used a Sherline, Unimat DB and small Atlas at work.

Emco Unimat 3 & 4 use 14x1mm thread
Emco Unimat DB & SL use 12x1mm thread
Sieg CO Baby Lathe uses 14x1 mm thread
Atlas and Clisby use 1/2"x 20 thread
Sherline & Taig use 3/4"x16 thread

Sherline manufactures chucks in all the above sizes. Arc Euro Trade sells the Sieg CO Baby Lathe and has it's accessories in the 14x1mm thread. 3/4"x16 and 14x1mm are the most widely available accessories.

From reports I have read the Cowells is a quality, well made, rigid machine, machined from castings and probably better than other models, some of which have non-metal components. The cross slide is longer and has tee slots for accessories and the vertical milling slide is a well made unit. I would as others have stated, investigate updating the spindle and possibly the tailstock barrel or even having a new spindle made. Even if it came to making a new spindle, I doubt you would be disapointed in the basic machine. Visit the Cowells website and see the setups pictured with the attachments.  I have made a number of accessories using the method outlined by Jasonb, leaving excess stock to be turned down on the spindle itself, turned for spindle nose register, reversed and finished turned.

[Jasonb]

As Bogs says ideally the thread should be screwcut if you have the right change gears and can be finished with a tap to give the correct thread form.

However on a small lathe like this I would say that the small length of thread will allow a bit of play for any errors in alighnment and the register and back face will be what pulls the backplate into line. Provided you then face the backplate when screwed onto the spindle it won't be far off.

As you say the tailstock chuck will unlikely hold a M14 tap, nor will the 3 jaw chuck likely hold the backplate. But a male or female centre in teh tailstock drill chuck will guide the tap to get it started, you will then have to transfer to the vice.

J

[Gbitz]

Hi again,

I would just like to thank you all again for your really useful, solid, practical advice - I now have a MUCH clearer idea of what I need to do.

Many thanks,

Andy