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Mini lathe chatter on facing cuts

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Fergal:
Hi all

I recently got a used 7x14 mini-lathe (Amadeal CJ18). I've not touched a lathe for 35 years since school days, so I'm probably doing it all wrong, however I have adjusted all the gibs so everything is tight and that has improved the finish on turning cuts. Facing cuts on harder materials (stainless & mild steel) suffer from bad chatter though. I don't think it's the tools as I have tried HSS and carbide on HDPE with good results.

if I pull on the cross slide there is some slight movement across the main axis of the lathe which I can't seem to get rid of without making it so tight that I can't move it anymore. I've tried adjusting the leadscrew nut and the gibs to minimise this movement. Are there any other adjustments or modifications I can make to improve the quality of my facing cuts?

Thanks

Stilldrillin:
Hold a piece of bar, in the chuck. Preferably, with a dti on the chuck.

Push/ pull etc, to detect any movement, in the bearings......

Adjust, with the two locknuts at the other end of the headstock.

Fergal:
So you think my problem is due to the headstock bearings? The previous owner changed them to the tapered ones and I've measured the runout on the spindle plate and it's about 0.01mm. I'll check them later.

Surely the movement in the cross slide can't be good? I think maybe I need to shim it as mentioned here:

http://www.mini-lathe.com/Mini_lathe/Tuning/tuning.htm#xbacklash

Peter Cordell:
I have a CJ18 i think there is a good chance this is your problem


these maybe helpful

http://madmodder.net/index.php/topic,10107.msg114760.html#msg114760

http://madmodder.net/index.php/topic,5406.msg57014.html#msg57014

bpud:
I have a Sieg C3 ("mini lathe", 7" x 14"), which I think is similar to the machine in question.  Have a look at the carriage/saddle gibs, the standard ones are pretty tacky and hard to adjust adequately.  I changed mine to tapered gibs and the difference is surprising, much, much better.  I used Bogstandards method, which may still be available here.  There are lots of other guides though.  Well worth the effort.
cheers
Bill

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