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wbleeker
07-24-2009, 04:49 AM
My new lathe is a chinese one from the Yunnan Machine Tool works, it is the equivalent of the CL40 sold in OZ by www.machineryhouse.com.au. I bought it off our local toolmaker who retired recently and couldn't find an owner for it, it is in great condition except for a section of leadscrew about as long as a credit card that appears to be badly worn around the crest of the thread, so the first thing I thought of was that perhaps at the factory they put in an imperial clasp nut instead of a metric one which could account for the wear, I had a bit of a fiddle with it and I closed the clasp nut (machine off of course) and rocked the saddle back and forward a bit and the clasp nut engaging lever jumped back out of engagement, so I think perhaps I am right, that probably it is not engaging all the way. Any one had any experience with this sort of thing?

.RC.
07-24-2009, 05:16 AM
I guess it could be worn....Have you priced a new leadscrew and half nuts??

wbleeker
07-24-2009, 05:31 AM
Half nuts will be here Monday, 135.00 AUD, Leadscrew not in OZ at the moment 1996 price was around 550.00 AUD. I have never seen a leadscrew with that amount of wear which is what leads me to believe that it has the wrong half nuts in it.And if I prove that is the case I will get the original owner and talk to the sellers as I think it should be still covered by warranty irrespective of its age.
Will

oldtiffie
07-24-2009, 05:35 AM
Will.

If you are considering any replacement, I'd open the apron first and see if there was a mechanical (ie "linkage") problem. It may be a simple fix. If it is only the top of the lead-screw and nut/s that are worn, they may only need a "touch up" and a re-setting - with no spares required.

Either way, the apron is going to be opened/removed - which may be for the best as you will be able to "see" instead of "guess" what the problem is.

This sort of thing can be caused by a good "crash" that may not be evident.

Machinery House aka Hare & Forbes aka HafCo carry a good range of spares for a lot of the equipment they sell. Some is carried in stock, other stuff is "ordered in" (from China - 4>8 weeks). I've had very good results both ways. Give them a ring and they will go through their spares and "master" catalogues and give you advice as to availability, cost and delivery time.

The Artful Bodger
07-24-2009, 05:57 AM
{Deleted by me, double post!}

The Artful Bodger
07-24-2009, 05:59 AM
If the leadscrew is toast what would be the prospect of swapping it end for end? I am assuming the damage is close to the headstock end.

.RC.
07-24-2009, 06:08 AM
A bit off topic but Will, what do you think of the Yunnan lathe???

I am looking for a 16"-17" swing lathe at the moment and wondering what you think of that model??

oldtiffie
07-24-2009, 07:36 AM
Half nuts will be here Monday, 135.00 AUD, Leadscrew not in OZ at the moment 1996 price was around 550.00 AUD. I have never seen a leadscrew with that amount of wear which is what leads me to believe that it has the wrong half nuts in it.And if I prove that is the case I will get the original owner and talk to the sellers as I think it should be still covered by warranty irrespective of its age.
Will

That's a nice lathe Will.

I was at H&F yesterday and was filling in time and had a look at the lathes - that one included. I couldn't run it but it looked nice and felt nice. All the required features too.

I just checked the H&F web site and catalogues. Warranty is not mentioned. In OZ, irrespective of anything else to the contrary - in a "Consumer" if not a "Commercial" environment - at the Retailer to Consumer level at least - there is the warranty of being fit for purpose, which my be limited or restricted to the initial buyer of the new item. It is usually 12 months unless other wise legislated or agreed (in writing). It is not usually transferable to successive buyers.

If the Tool-maker had no complaints, and given that he would - or should have been an informed buyer - the lathe passed all tests.

If the Tool-maker sold it to you on a "as-is where-is" basis without a written warranty, you may have trouble getting any settlement.

I can't see that the lead-screw problem could be classed as "fair wear and tear" - and if it were, in whose hands did it occur?

If it were me, I'd just "wear it".

On the several occasions that I've had (only minor) problems, I've always had a very good result from H&F.

wbleeker
07-24-2009, 06:13 PM
Thanks for the replies everyone, the leadscrew can't be turned end for end there is a section at the right hand end with no screw, Ringer I haven't used the lathe yet, just got the outlet put in yesterday, I am having a hernia operation on Tuesday so it may well be a couple of weeks before I get to have a go at it, Tiffie I will probably just wear it, I ordered the half nuts as they were in stock and good for a comparison anyway and 135.00 isn't going to break the bank, the bloke I bought it off rarely did any threading and had quite a terrible shed to work in so I think he probably didn't even notice the damage, he is a long term family friend, I actually used to help him out when I was an apprentice.
Will

Robin R
07-25-2009, 01:21 AM
If it came to replacing the leadscrew, you would nave nothing to loose by trying to re-work the existing leadscrew. What might work would be cutting the leadscrew at both ends, leaving the same length at both ends of the leadscrew. Next bore both ends of the leadscrew and the matching ends that you cut off, to match a piece of bar of a suitable size. You could then Loctite the bar in the bored holes and cross pin it to take the torque.
You would still have the bad bit of thread in the leadscrew, but you would just have to position your workpiece to avoid that part of the leadscrew.

speedy
07-25-2009, 02:55 AM
Au$550 is incentive enough.
Yeah Will, as Robin suggested maybe you could cut, bore and spigot both ends. Or weld then machine.
I plan on doing that with the Myford one day .....when I dig it out from under the debri :)

Retires to couch and waits for response from Allan..............................

The Artful Bodger
07-25-2009, 04:50 AM
Will, regarding flipping the lead screw, if your carriage has the feed wheel to the right (which I understand is the European tradition) then you are likely right but if the feed wheel is to the left, American style, the half nuts are presumably to the right and hence you could tolerate a bit of non-tread at the left hand end. Just a thought.

philbur
07-25-2009, 07:03 AM
I would have thought that it is impossible to fully engage imperial half-nuts on a metric lead screw. Surely jumping out of engagement indicates a faulty or worn engagement mechanism.

Phil:)


Half nuts will be here Monday, 135.00 AUD, Leadscrew not in OZ at the moment 1996 price was around 550.00 AUD. I have never seen a leadscrew with that amount of wear which is what leads me to believe that it has the wrong half nuts in it.And if I prove that is the case I will get the original owner and talk to the sellers as I think it should be still covered by warranty irrespective of its age.
Will

speedy
07-25-2009, 09:17 PM
Will, I remembered that I have a near new imperial leadscrew tucked away in the shed. It is off a Bramley 1240, maybe suitable for yours? I have sent you a pm.

wbleeker
07-27-2009, 06:29 PM
I got the new half nuts yesterday so I pulled the apron and leadscrew, and feedshaft off. What I found was that the bottom half nut was packed to the brim with swarf which was not allowing proper engagement, as well as this most of the screws holding everything together were loose. Off to hospital this morning so I won't get it back together for a few weeks.
Will

Rustynutz
08-05-2009, 05:16 PM
In the past I have re cut the old screw thread parallel then made a new nut to fit. This quick fix I done to my Abeny mill some 15 years ago and still working fine and also the cross feed on my Myford about the same time. if parts are expensive or impossible to get hold of this might be your answer.
only problem is you need a machine to fix a machine.best of luck
N.B if your old screw is to soft for the job you might consider hardening after re cutting it.

wbleeker
08-09-2009, 04:58 AM
got the operation all done and couldn't wait to get it back together, What I found when I put the new nuts in and went to tighten everything up was that when tightened up it was impossible to operate the half nut engaging lever, ie everything locked up due to no clearance in the ways that the half nuts slide, so I put each half nut in the vice and ten strokes with a good file fixed everything. I could have measured what needed to come off and machined it off but IMHO a bit of humble basic fitting solved the problem in a short time.
Will
I haven't tried screwcutting on it yet but it looks like the wear is only on the outer edges of the leadscrew so I think it should work alright

Circlip
08-09-2009, 07:52 AM
If you're going to have to replace the leadscrew, I would be inclined to look for a homeland produced item, at least the steel will be fit for purpose.

Regards Ian.

oldtiffie
08-09-2009, 09:42 AM
got the operation all done and couldn't wait to get it back together, What I found when I put the new nuts in and went to tighten everything up was that when tightened up it was impossible to operate the half nut engaging lever, ie everything locked up due to no clearance in the ways that the half nuts slide, so I put each half nut in the vice and ten strokes with a good file fixed everything. I could have measured what needed to come off and machined it off but IMHO a bit of humble basic fitting solved the problem in a short time.
Will
I haven't tried screwcutting on it yet but it looks like the wear is only on the outer edges of the leadscrew so I think it should work alright

Good for you Will.

Looks like a good week for you with good results from the operation and on your lathe.

Nice solution too to ease the nut/s with a file - by hand - too.

The tops of the thread don't matter at all - as long as the sides/flanks are OK you are set to go.

The lead-screw (uncovered??) is a dead-set way of carrying swarf etc. into the innards of your apron. It almost acts as a screw-conveyor or a mincer.

I'm surprised that no-one else took the hint and checked their own lathe aprons for the same problem.

At least you know you can get spares for your machines when you need them - but a lot of the "Old American Iron"
fans and "China-knockers" may not be as well off if and when they need those sorts of support and spares.

That is a nice machine you have. If I was in the market for a new lathe, that one of yours would be well and truly on the list.