Lathe cross slide problem

[Kingchristo]

Hi everyone on my portass lathe model s when I turn the cross slide screw it turns the handle someway before it starts to move the cross slide what is this called and is there a way to lighten this up. Ive looked on ebay for a new screw for it but can only find one for the myford lathe.

 

[bazmak]

its called backlash and every machine suffers from it,exept the very best and expensive.If you allow for it when setting the cross slide it is accepable but
again it depends how much.Please estimate ahow many thou on the dial before the slide starts to move.It can be adjusted out,i doubt if its the screw more likely the nut.Some have adjustment.More info and a few photos would help
I understand you are a newbie but more info would help us to understand the extent of your problem.As stated before it makes it difficult if you start a new thread everytime you hit a problem.OIpen a thresd on the Portass lathe
and put all your questions in with a title Regards barry

 

[Brian Rupnow]

On my lathe, the cross slide threaded rod engages with a nut below the cross slide. When I was taking things apart to install a quick-change toolpost I noticed that the cross slide nut is split about half way through, with a pinch bolt that can be tightened to close the threads on the nut up a bit and get rid of too much backlash.

 

[goldstar31]

Brian's suggestion is excellent but sometimes this is not possible if the nut is solid and if it is zinc alloy, it becomes more difficult. I have carefully nipped the zinc alloy nuts such as on Myfords but brass/bronze solid nuts can be tinned with solder. I did this on an old Pools Major many years back.

The feed or leadscrew is blackened with soot from a candle and the nut itself is carefully tinned and literally recut with ' brute force and bloody ignorance'

Another wheeze is to split the nut partially and follow Brian's words and music.

Nobody's suggestions can work properly if the screws themselves are badly worn.

However( However) there is yet another idea and that is to use studding.

I used this way back when I built a Westbury mill/drill from- very porous castings.

Coming back into the 20th Century, my Stent t&C has 3/8th BSF studding as 'standard' feeds.

Of course, cheap vernier slide gauges are available and save much head scratching on old lathes.

I hope that this helps

Norm

 

[JCSteam]

Norm is correct, if backlash is something your struggling to cope with, then a digital vernier, adapted to fit on the two bodies of the cross slide will help no end. You could even use rare earth magnets instead of bolts, so long as it's aligned correctly and parralel it takes a lot of guess work out of dialing in the dials. Though I'm happy to say backlash is something that is easy to come to terms with just turn the handle out a full turn before turning in back into the work and dialing in the size you want.

Norm your suggestion on soldering the hole sounds a good bodge to improve matters. My myford (1940"s) has upto 20thou on all the dials and leadscrews, I'm wondering how much the solder trick would work. I was thinking of fitting a bush instead and drilling the original casting out to size to take the bush. Cutting the thread so the tops of the nut are wider by 20thou. Certainly try your idea first as it's much less work lol.

 

[goldstar31]

Of course, the idea of using solder- or any other 'female' part depends on how worn the male bit is. Oh, dear but really it does describe things.

If the male thread is worn- somewhere, there isn't a great deal which might improve things other than a new screw. Again, if the nut is alloy, it might be nipped up( carefully) or packed out with one of these Devcon/Turcite/ or something similar 'might' suffice.

I must emphasise that this gender thing is intended to help on lathes. What two people do standing up in a hammock together is non of my business

Cheers

N

 

[JCSteam]

I must emphasise that this gender thing is intended to help on lathes. What two people do standing up in a hammock together is non of my business

Cheers

N

Probably fall over, you ever tried to get into a hammock? Let alone stand in one, easily break something, probably an appendage! :-\

 

[dennisa49]

Good day, I have a Hare and Forbes 9 X 20 machine. I asked this question some time back. A few weeks ago I needed to tighten the retaining nut on the cross slide wheel. I found there is a grub screw in the centre of the wheel. By tightening the screw the slack was removed, I now have minimal backlash in the cross slide. I can be reduced to zero, I have set it to zero minus about a tenth of a graduation movement. This equates to a thou or so, enough to leave a good travel movement.

Check your cross slide wheel, you may have the same type of adjustment.
Regards, Dennis

 

[bazmak]

Even if there is no adjustment you can easily fit some method
The Chinese started by rocking the nut and then fitted a screw to a
split in the nut. Also look at at fitting a tension screw with a nylon insert
to bear on the thread.All will work if the screw is not too worn

 

[goldstar31]

Even if there is no adjustment you can easily fit some method
The Chinese started by rocking the nut and then fitted a screw to a
split in the nut. Also look at at fitting a tension screw with a nylon insert
to bear on the thread.All will work if the screw is not too worn

I also recall that the Chinese lathe manufacturers split the feed nuts on the 918/920 lathes and my 9180 which a Myford spindle version had these.

Again, as Baz rightly explains, another variant was to bend the feed screws which probably pulled an unworn/less worn part of the nuts into use. We can argue about the standard of engineering- or perhaps others!

Again, I recall that I have mentioned the existence of the follow up article in December 1988 in Model Engineer of how the late david Lammas made a tap and die for a friend's early Myford.

Somewhat scurrilously, the original poster who raised the question has vanished in to the sunset- somewhere.

Whatever the comments which might arise, the information was given, and raised and sank without trace.

It's a depressing thought

Norm