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John R
10-20-2006, 08:34 AM
Can someone tell me how to take the backlash out of a Phase II, 6 inch rotary table. I have rotated the worm assembly to the limit of its engaged position but still too much backlash.
thanks
John R

SGW
10-20-2006, 08:52 AM
I suspect you don't. Like all screw-feed mechanisms, there will always be some amount of backlash, which you deal with by always taking up the slop in the the same direction, the same as you have to do with milling machine table feedscrews or a lathe cross slide.

GRH
10-20-2006, 10:45 AM
Is this a new, near new or old rotary table.

Graeme

John R
10-20-2006, 10:58 AM
GRH
It is not old but it went through a hurricane. I took it apart as far as I could, cleaned out the mud and put it back together. Every thing seems to be OK except the backlash. There is now a lot of backlash where before it was hardly detectable. I think I have heard of ways to correct but I don't know
Any help will be appreciated
thanks
John R

Herm Williams
10-20-2006, 11:34 AM
I have a different brand but if it works the same as mine the worm has offset bushings to adjust for gear mesh play. Basicly the bushings at each end of the worm are not drilled in the exact center so you can turn to take up slack. End to end should have a thrust bearings or bronze washers.
my two cents worth
re

dp
10-20-2006, 11:35 AM
If it is end play in the screw then that should be correctable with some manner of shimming or adjustment, but if it is from loose coupling between the screw and the worm gear you may have a persistent problem.

The cross and compound slides on my lathe has both problems so I'm replacing the screws and nuts. I'm beginning to think Chinese lathes should be called 'kit lathes'.

pcarpenter
10-20-2006, 11:55 AM
DP-- I don't know which Chinese lathe you have, but mine has split nuts on the cross slide and the nuts are also somewhat adjustable for "position" (to prevent lead screw binding), so you may want to look for this adjustment. Usually the lock screws are above the location of the feed nut on the cross slide, with the heads appearing on the top of the cross slide. The lousy instructions with my 13x40 tell how to adjust backlash.

Too often compound feed nuts are not adjustable for backlash...and that is not just a chinese thing. Still, you may be able to change that.

Even my 7x14 mini lathe had this feed nut centering adjustment. I also took it apart, drilled the square feed nut lengthwise in two corners for small pins, and then split the nut, such that even it is adjustable to remove most backlash.

Backlash exists in all feed screws to some extent with the exception of those that use ballscrews. It is not inherently evil. If you adjust it away until you only have .002 instead of .020, you still cannot ignore it. You can adjust out most of it on many things, but the right answer will always be to remove the slack when feeding by always feeding in a single direction into the work.

Sounds like someone already gave the right answer to the original question. If you put back any shims where they were and now have more backlash, look for offset bushings that account for adjustment that might not have been observed during re-assembly.

John R
10-20-2006, 05:41 PM
thanks all
I appreciate the help
John R

Lou
10-20-2006, 06:30 PM
I have a Phase II also, and the backlash is adjusted as described by Herm..

lane
10-20-2006, 08:33 PM
I thank you know how it works if you took it apart to clean it up. the worm runs through an eccentric shaft that rolls in and out of mesh with the gear. BUT their is wsually a set screw that limits the travel. Sounds like the set screw is screwed in to far. LOOK FOR the set screw should be somewhere nere the lock leaver toward the bottom.

daryl bane
10-22-2006, 11:53 AM
Alittle late to the party. I have a Vertex super spacer that I considered way too much backlash. The handwheel shaft/worm had too much endplay and no real provision for correcting it, except crudely. I machined the eccentric shaft bush to accept 3pc thrust bearings on each end, as mentioned in a previous post. The worm and gear were then lapped together in place. This ,plus scraping the table and chuck, now make a very fine tool.

Millman
10-22-2006, 12:18 PM
Some of the Big boys had the eccentric, as Herm mentioned. They were so smooth, once you got them dialed in.