Warco WM250V Cross Slide Nuts

[Mick B1Participant @mickb1]

I was recently facing a component and didn’t notice in time that the cross slide was reaching limit of travel. I heard the power feed starting to labour, but the shearpin didn’t shear (despite a groove I’d put in it) and by the time I’d knocked off the crossfeed the cross-leadscrew and nut had jammed.

I thought of trying to back out of the jam by reversing the feed tumbler and re-engaging, then rotating the chuck by hand – but the outcome was unclear and I didn’t like the feel of it. However it was enough to enable me to unjam it by hand and finish the job after correcting the tool position.

Now the cross slide handwheel was distinctly – but not unusably – stiff to turn over the whole travel except for the last few turns clockwise (away from the user) before the stop. Having seen a picture recently of the slotted cross slide nut, I guessed the leadscrew might’ve bent, or summat might’ve happened to the slot.

I asked Warco for a quote for the leadscrew and they replied – as suspected by a recent-ish poster on here (I can’t now find the posting) – that they supply leadscrew and nut as a matched pair at a gnat’s under 60 quid, plus VAT and Carriage.

Well, I took out leadsrew and nut and had a look. The leadscrew wasn’t perceptibly bent, but once I had them in in isolation from other possible factors, it was clear that the nut was stiff on the screw when both the thick and the thin bit of the nut were engaged.

You can see the incident had cracked the thin bit on one side. It had also visibly caused the slot to be narrowed on the cracked side – the picture was taken after I’d used the little jacking screw on that side to open it out visually parallel again.

I then found that the leadscrew ran in the nut apparently as smoothly as before the collision. When I reassembled, the backlash in the handwheel was still 0,2mm (on diameter, so 0,1-ish actual) or less over nearly the whole travel, which is better than any industrial lathe I can remember working on in industry. So I don’t plan to pay out for doing anything further unless I run across further problems. Obviously it’s cracked now, but AFAICS it’d take another collision to finish it off, and it seems good enough for all normal work as iti is.

So my guess is that the way they match the pairs in the factory is to close up the slot slightly by bending the thin side inwards, the screw it onto the leadscrew and adjust the small jacking screws to open it up until they get the fit  they’re looking for.

[Tony Pratt 1Participant @tonypratt1]

Every time I see a piece of Chinese machinery in detail it becomes obvious that they do the absolute bare minimum engineering wise to achieve a sort of workable product, this is how they have over run western industry!

And BTW I have a Warco 290V lathe which I absolutely love but scratch the surface and its a pile of Cr**, the cross slide nut picture reminded me of that.

Tony

[Mick B1Participant @mickb1]

I suppose it’s a case of how much you care for cosmetics. The things that matter about that nut are the accuracy of thread fit and the top face to thread CL distance and parallelism. I thought about tidying the finish with file and emery, but nobody’s gonna see it in normal use, and generating a load of abrasive debris around it would just give me an extra cleanup job.

Handsome is as handsome does.

Although it does look as if it was 3d printed out of metalised RAAC… 🙂

[HopperParticipant @hopper]

Cheap is as cheap does. But it gets the job done at a budget price. As you noted, backlash on the cross slide is no big deal if you know enough to wind the handle past the backlash and then back to where you want it, as is common practice  on the industrial lathes you have used.

You have a lathe, you can always make up your own nut to suit if required. I made one for my old Drummond lathe. An interesting little project to while away an afternoon. But if the current one works as is, all is well.

The cheap is as cheap does philosophy seems to be becoming universal and not unique to tools etc. Household appliances that young couples once received as wedding gifts and were still working when they retired have been replaced by junk that lasts a year or two.

Even down to silly things like clothes pegs. I had to buy some new ones recently and they basically don’t work. They twist and either jam up or fall apart. Inspection vis a vis the old pegs reveal the wooden parts are identical but the spring is wound from the next gauge thinner wire and and this flexes too much and does not hold the peg together in operation. Cheap cheap. And mops whose strings are held to the main body with two ungalvanised staples so they rust out after about one year and fall apart. Now I note the store sells mop “refills” of the exact same poor quality that you screw onto the old handle. Planned obsolescence. Right at a time when we should be cutting back on consumption to save the baby whales etc… Geez, don’t get me started.

[Hopper]

On Hopper Said:

… Geez, don’t get me started.

Sounds like I already did… 🙂

“Give them the third best to go on with; the second best comes too late, the best never comes.”  (Robert Watson-Watt)

Overall perfection doesn’t actually exist. Exact match for one task means drawbacks for another, in practically any piece of equipment you can imagine.

As far as I could see at purchase, the Warco did more things, and did them better, than the competition – at least with the addition of the versatile milling slide I already had – and I’m not aware of any significant change 9 years later. Capability has its own quality, irrespective of the cosmetics.

[BazyleParticipant @bazyle]

Getting back to the sbject.

Have a think about how the screw/nut performs in this application. 99% of lathe work is designed to run the slide inwards ie away from the operator so the ‘thick’ part of the nut provides multiple threads engaged to take the force and spread wear.
The thin part is only there to adjust backlash for your convenience. Most smaller hobby lathes don’t have any such provision so actually it is a mark of increased quality/thought by the supplier.
Again think carefully about the thread in contact when you have the slot adjustment loose and alternating between directions of travel. When moving the slide towards you only the few threads of the thin bit are in contact and taking all the load; no wonder it bent.

The manual should have told you how to adjust this backlash. Since you have it apart you can make some careful adjustments and assess the variation in backlash along the screw, if any on a new lathe. Also look into what provision is made on teh lathe for getting proper lubrication down to the nut.

[DC31kParticipant @dc31k]

Maybe it cracked because the grub screws crossing the slot were not snug when the overload happened. If the slot in the nut were properly bridged, there is no way the thin part can deflect in that direction.

If you were worried about the gap closing up despite the grubscrews, buy some crinkle washers of the appropriate size and jam as many into the gap as makes a snug fit. Crinkle washers are thin so you can make fine adjustments. Then if the nut tries to bend again, the washers provide a solid path of resistance.

Re-engineer the nut so that the holes in the thin bit are clearance holes for studs screwed into the fat bit. Then with nuts either side of the thin bit, you can bias the slot open or closed and it will be restrained in both directions.

[DC31k]

On DC31k Said:

Maybe it cracked because the grub screws crossing the slot were not snug when the overload happened. If the slot in the nut were properly bridged, there is no way the thin part can deflect in that direction.

…

That’s really what I think happened. Although the open end of the slot on the cracked side was narrower than the blind end, there was still a few thou daylight showing between the tip of the adjusting screw and the inner face of the slot it should’ve been bearing on. The screw head was burred over, so I had to re-saw the slot to adjust it to contact. So it looks as if it wasn’t fully supported from the start.

I don’t know whether the collision created the head burr or it was there from manufacture. But I have to suspect the latter as that would have made it difficult for the assembly fitter to set it correctly and encouraged him/her to let it go set on one side only.

And it’s a bit late after 9 years’ effective service to try a warranty claim, innit?

🙂

BTW I agree with Bazyle that the presence of the adjusting slot shows thought about provision for wear and tolerances that I’ve not been aware of in other makers.

[Hugh Stewart-Smith 1Participant @hughstewart-smith1]

hello Mick,

If  you find that you do need to replace the 250 leadscrew nut, we stock these sourced from our supplier Weiss and retail the part together with the matched leadscrew at £35 including VAT and delivery. They will almost certainly be interchangeable with your machine.

Hugh                                                                                                                                                                    Amadeal Ltd.

[Mick B1Participant @mickb1]

Thank you, Hugh,

Is it a 2mm pitched screw?

I’ll certainly bear that in mind.

[Hugh Stewart-Smith 1Participant @hughstewart-smith1]

yes indeed Mick, 2mm pitched screw

H.

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