How much saddle wear is too much?

R

Raydel

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In attempting to get rid of most of the backlash and slop in the various parts of my SB 9A, I removed the saddle to inspect wear on the underside. The rear "V" grove of the saddle has a raised ridge on the lower edge (the edge that runs OFF the ground surface of the Way), that measures .017" above the ground surface of the saddle. Both sides of the V have the same .017" ridge. The front V grove measures approx. .007". My reasoning is that this saddle wear has caused the entire carriage/saddle assembly to sit lower in relation to the rack, causing the pinion gear not to mesh with the rack as snugly as it should. The pinion gear does have it's own wear, but I can eliminate nearly all of the backlash by gently lifting the saddle/carriage assembly slightly off the ways.
Should I be concerned about this saddle wear and what can I do about it.
Needless to say, wear on the ways is my next concern.

Thanks for your valuable input.
Ray
 
It's a trick question right? Any wear is bad wear, the severity affects most lathe operations that traverse from the good to the bad areas. I inherited my grandfathers Atlas lathe from my uncle about 40 years after I first saw it in G'pa's basement. By the time I got it the ways were bowed (worn) .025", the saddle .0145", the cross slide .003". It took a week of hand scraping to get the bed flat.

If you want it corrected your SBL will need to be scraped as well. The V ways make it much harder than my flat wayed Atlas.

If it works for you as-is, try to keep your high tolerance work short. Otherwise start reading up on scraping.
 
I don't know if this is much help but, I believe the only way to not have wear is to buy a lathe new. That being said, I have worked around old worn and well used equipment a long time. Yes , it can be a problem on close tolerance work, but once you learn YOUR machine , you will get used to working around the wear problems. My old SB 9 has wear on the ways and saddle in the middle ( someone must have done a lot of repetitive stuff in that area) and once I got used to it, It doesn't bother me much. I just work with it and I make some items that require a decent fit when done.
I wouldn't jump into scraping and trying to make it "like new". Use it , enjoy it, and maybe you will find as I did " It ain't so bad the way it is". This is merely my opinion though. If the wear is so bad you can't work with it, then you will have to figure out what to do about it.

Mark Frazier.


A note: I replaced the compound and cross slide nuts in my 9 inch lathe and machined the screw shoulders to get the backlash down to a couple thousandths there and it helped more than anything else I could have done and those are easy fixes.
 
Raydel said:
In attempting to get rid of most of the backlash and slop in the various parts of my SB 9A, I removed the saddle to inspect wear on the underside. The rear "V" grove of the saddle has a raised ridge on the lower edge (the edge that runs OFF the ground surface of the Way), that measures .017" above the ground surface of the saddle. Both sides of the V have the same .017" ridge. The front V grove measures approx. .007". My reasoning is that this saddle wear has caused the entire carriage/saddle assembly to sit lower in relation to the rack, causing the pinion gear not to mesh with the rack as snugly as it should. The pinion gear does have it's own wear, but I can eliminate nearly all of the backlash by gently lifting the saddle/carriage assembly slightly off the ways.
Should I be concerned about this saddle wear and what can I do about it.
Needless to say, wear on the ways is my next concern.

Thanks for your valuable input.
Ray
Click to expand...

Can you shim the rack?
 
Why are we worried about backlash in the carriage? Is it bad enough that the gear and rack are not engaging correctly? If you turn the carriage handwheel left and right and there's a bit of play that's really not an issue.
 
When the carriage casting rubs against the top of the bed v-ways. Remove the wiper retainer and look for a slight gap between the casting and the top of the bed vway. If you have a long bed, you can slide the whole heastock up a foot or so.
 
It is inconvenient if there is a lot of play and as long as that is the only problem, shimming the rack will make the lathe more pleasurable to use. I myself use the hand wheel a lot and a lot of play going back and forth would bother me and I would probably do something about it if it is excessive. It is a matter of personal preference. But I would only shim the rack if that is the only problem affecting the use of the machine. The saddle wear can be worked around unless it causes interference somewhere. Using the hand wheel to sneak up on a turned shoulder can be very difficult with a lot of play there.

Mark Frazier
 
Thanks to all who offered tips and advice. I'll systematically work my way through the individual components contributing to sloppy controls and leave bed and carriage wear for the last if at all possible.
Mark_f, we're on the same page. A lot of hand wheel play does bother me, so I'll try shimming the rack as a last resort.
Will post final results here after all is said and done.

Thanks again to all the good helping folks here.
Happy chipping (and I'm not talking "Golf"). :)
Ray
 
Raydel said:
Thanks to all who offered tips and advice. I'll systematically work my way through the individual components contributing to sloppy controls and leave bed and carriage wear for the last if at all possible.
Mark_f, we're on the same page. A lot of hand wheel play does bother me, so I'll try shimming the rack as a last resort.
Will post final results here after all is said and done.

Thanks again to all the good helping folks here.
Happy chipping (and I'm not talking "Golf"). :)
Ray
Click to expand...
Ray,

If you shim the rack , and a small shim there is not a bad thing, you want to use a full strip of shim under the entire rack surface and it won't be very thick. Do not try to just shim under the bolts. ( I've known someone who tried that and it is not nearly as good.) You will always have a little play. It can't be too tight or you will get spots that bind.

Mark
 
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