Slack in my compound.

[littlejack]

Hey fellas:
I went out today and made a sleeve for my collet puller. The puller shaft/tube was a little too long to tighten up against the chuck spindle
and pull the collets tight.
This is for my (new to me) QC54 Atlas. This sleeve came out very nice. This is my first piece of usable tooling, as all before has just
playing with the machine, and getting to know its quirks.
Anyway, The lathe seems to be very accurate. The only issue I found was the play/slack to and fro in the compound. It is not that big of a
problem, as all one has to do is keep the compound loaded against the threads, depending on which way you are cutting/boring.
However, I would like to tighten things up at least some, and hold tolerances better. I am sure that this has to have a bearing
on vibration issues?
Question:
If I install a new brass nut in the cross feed, will that eliminate all of the slack, or will there still be some but not as much? I suppose, there
could be worn threads on the threaded rod as well, but the brass is supposed to wear before the steel threads, correct?
How much slack is too much?
Regards
Jack

 

[xalky]

Backlash in the feed screw is pretty normal and shouldn't affect accuracy all that much. I would look at the gibs on the compound to eliminate vibration and chatter. Operating a compound with tight gibs can be a little harder to feed in, but it should keep things where you set them when making a cut.

 

[wa5cab]

Jack,

Even with a new nut and feed screw, you are going to have around .005"-.010" backlash. I probably wouldn't both replacing the nut until the backlash exceeds .030". You already know about approaching the working setting always from the same direction, which washes out all of the error it's possible to do anything about. Or to put it the other way, If you know what you're doing, you can get just as accurate results with .030" backlash as you can with anything less. If you suspect that a vibration problem exists and you don't need to move the compound or cross slide during a pass, you can also replace the center gib screw (on the cross slide the 2nd one from the crank) with the T-handle gib lock screw normally supplied with the milling attachment.

Robert D.

 

[Mondo]

Jack,

Even with a new nut and feed screw, you are going to have around .005"-.010" backlash. I probably wouldn't both replacing the nut until the backlash exceeds .030". You already know about approaching the working setting always from the same direction, which washes out all of the error it's possible to do anything about. Or to put it the other way, If you know what you're doing, you can get just as accurate results with .030" backlash as you can with anything less. If you suspect that a vibration problem exists and you don't need to move the compound or cross slide during a pass, you can also replace the center gib screw (on the cross slide the 2nd one from the crank) with the T-handle gib lock screw normally supplied with the milling attachment.

Robert D.

'Zactly. I replaced all my gib screws with allen-head screws. I can make minor adjustments with my fingers, and tighten a little more with the Tee-handle hex wrench I keep handy.

 

[littlejack]

Thanks for the replies fellas.
I went measured the amount of backlash, and it is .012 - .015, depending on how much pressure one pushes or pulls. From what you all
have said, that is acceptable.
That is fine with me. It is just one of the things to remember when using the machine.
Gib screws are adjusted, so there is no slop in the gibs , but may well change them out for the allen head type.
Regards
Jack