Warco WM250V – Cross Slide Screw Replacement

[John McCullaParticipant @johnmcculla]

[John McCullaParticipant @johnmcculla]

Hi all,

The nut for the cross slide screw on my Warco WM250V lathe broke a while back (the narrow section after the slit for adjustment broke off), and Warco sent me out a new nut and cross slide complete under warranty. It sat in a drawer for a bit as the old cross slide nut was still working, however today I noticed that I suddenly had approx 180 degrees of back lash on the cross slide. I assumed that the nut had failed further, so I decided now was the time to fit the new part. Upon removing the top slide, I noticed that the the single bolt passing through the cross slide and into the cross slide screw nut was very loose. This seemed to be causing the backlash, however I decided to crack on with the replacement. Upon removing the old screw, I have two questions.

1. There doesn't seem to be any support for the end of the screw, it just floats. The front is supported at the handle side, and the nut is bolted to the cross slide, but that's it. Surely that isn't a great design? Or is that the norm on these lathes?

2. The screw that I have been supplied doesn't have a drilling for the roll pin which holds the gear for the power cross feed. Either they have sent me a screw for a machine without that feature, or else they all come like that and I'm expected to drill it. It doesn't seem to be hardened, a file marks it easily, but my question is how do I drill through the piece squarely and in the middle of the rod. I don't have a mill, just a lathe (which would need reassembled temporarily to use) and a pillar drill. Any suggestions would be appreciated.

[John McCullaParticipant @johnmcculla]

[Clive Brown 1Participant @clivebrown1]

I'm not a Warco lathe owner, but I think that the lack of end-support for the cross-slide screw is fairly normal, at least on hobby-sized machines.

Re the roll pin. The lack of drilling may stem from the difficulty of accurately matching the cross holes in the two separate components. They need to be drilled together. Do you really need to fit a new screw on a lathe that is new enough to be under warranty, or only just out of it?

[John McCullaParticipant @johnmcculla]

I possibly don't need to replace the screw, however for two reasons I was going to. Firstly, I only needed a nut, but Warco sent a nut and a screw. This made me wonder if they came as a matched pair? Secondly, with everything bolted in place apart from the bolt that goes through the cross slide into the nut, I noticed that the nut wants to sit slightly to the side and out of line with the bolt hole. This made me wonder if something was bent or misaligned with the old screw, causing the old nut to be under pressure and break, so I thought I'd replace both the nut and the screw.

[David George 1Participant @davidgeorge1]

Hi John. It may be possible that there is some play in the holes which bolt the plate to the front of the slide which allows you to align the leadscrew with the nut as you assemble. Loosely screw in the leadscrew with screws loose in the plate that bolts it to the slide and the same for the nut. Then screw the leadscrew all the way in till almost as far as if will go then tighten the bolts and the screw should be in alignment and tighten the screw holding the nut as well.

David

[John McCullaParticipant @johnmcculla]

Hi David, I will certainly try that when I'm assembling it. I even wondered if I might need a small washer/shim behind one of the two bolts which hold the hand wheel assembly onto the cross slide in order to align everything properly so that when the bolts are all tightened up nothing is under pressure.

[Mick B1Participant @mickb1]

I wonder if your nut broke because the crossfeed screw's driven by a roll pin through the pinion?

My WM250V had a brass shearpin, not a roll pin in that position. Presumably the theory was that the pin would break if the crossslide met heavy resistance under power feed.

What actually happened in my case was that the brass pin broke when I engaged crossfeed by mistake and caused a severe collision (IIRC I was working late at night on summat), and one of the bits left in the crossfeed pinion fell out into the apron gearbox, jamming it perfectly. I had to take it off to find out what had happened, and clear it.

I made a new brass shearpin with a light tap-fit, to reduce the chances of bits falling out next time – and have had no trouble since.

Reading what you found, plus the chance I had of examining the Chester equivalent lathe at my son's workplace, has led me to think that there's some variation in final assembly of these machine – possibly different factories and very likely different individuals with their own procedures. For example – the Chester had a brass shearpin driving the longitudinal leadscrew, whereas my Warco had what looked like silver steel, and now you've found a roll pin in the crossfeed drive.

Whether you put back the rollpin or replace it with brass probably depends on which sort of jam you're more scared of…

 

Edited By Mick B1 on 27/07/2023 10:01:03

[John HaineParticipant @johnhaine32865]

This is Warco's responsibility, don't dilute it!

[Mick B1Participant @mickb1]

Posted by John Haine on 27/07/2023 10:36:11:

This is Warco's responsibility, don't dilute it!

If that's a response to what I posted above, I don't understand it.

Warco appear to have done their bit by supplying nut and leadscrew. They did so with me when I had a breakage during the warranty period. I suspect that if they had to keep mobile engineers on hand to travel to user site, analyse and rectify anything that arose within warranty irrespective of cause, their overheads would raise their prices to overtake Myford's.

[John McCullaParticipant @johnmcculla]

Thanks Mick, I toyed with the idea of making a brass pin but just decided in the end to stick with the original roll pin. I can also see why Warco didn't drill the hole themselves, because the hole through the gear was not on centre, so a perfectly drilled hole wouldn't have worked. I set the gear up in the drill vice so that it was perfectly in line with the drill bit, then inserted the screw to the right point and drilled it. This left everything lining up properly, but if you flip the gear 180 degrees, the hole doesn't line up, showing the original hole was off centre.

I think my next problem though does merit a phone call to Warco in the morning.

With everything built up the bolt hole in the cross slide nut still doesn't line up with the hole in the cross slide. By leaving the two front bolts slack as David suggested I can get the bolt in, but tightening up the front bolts then results in everything going very tight and/or binding up completely. I tried shims at one side of the front plate, this moved the nut to the correct position when the cross slide is in the middle of its travel, but when moved to either end the nut moves too far to the left at one end, and to the right at the other. Now this suggests to me that nothing is bent, but that either the bolt hole in the cross slide, the hole through the handwheel front plate, or the hole in the saddle casting, have been machined off centre. I think the issue could be solved by the machining of a custom lead screw nut, but I don't really want to have to do that. I'll speak to Warco tomorrow, and hopefully they can provide a solution.

[John McCullaParticipant @johnmcculla]

[Mick B1Participant @mickb1]

I just measured the position of the crossslide nut capscrew counterbore on my Warco with a caliper and it looks to be about 0,5mm off-centre. I don't have any noticeable difference in tightness from one end of travel to t'other, and backlash is pretty constant at about 0,2mm on the (diameter) dial – that's 0,1mm actual travel. Machine's had regular use for over 8 years now.

Measuring your pic, your counterbore offset looks less than this (as far as I can tell with a rule ) , and if the nut position relative to it differs between one end and the other, it looks as if it might be the angle of the saddle face, the bearing housing face or the bearing seating itself that's out of square?

It's definitely a legitimate question for Warco to look at in any of those cases.

Especially since you now have a reason to suspect why the original fitter left the capscrew loose.

[old martParticipant @oldmart]

Can you turn the nut around? Maybe the holes are both offset. If the plate at the front has any sideways adjustment, that might help.

[John McCullaParticipant @johnmcculla]

I spoke to Warco yesterday who said it's most likely that the plate at the front is has been drilled off centre, and they're sending me out a new one to try. Could be a slow process if that's not the issue and other parts need to be sent out, but at least they're trying to sort it. I must say they were very helpful.

Old Mart, the hole in the nut doesn't appear to be offset, but if nothing else works I think a nut made with a custom offset hole would solve the problem.

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