Carrige gib adjustments

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RSG
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Location: Ontario, Canada

Carrige gib adjustments

Post by RSG »

How loose should the gibs on the carriage be?

I've owned my lathe from new for about 8 years now and have adjusted the gibs on the carriage once since. As with most lathes the first 2" to 3" closest to the chuck on mine has experienced the most wear. When you crank it away from the head stock you can feel it tighten up a bit. When machining close to the chuck the carriage will actually push away a few thou during a facing cut if you don't hold the handle while taking a moderately heavy cut.

I feel that the adjustment I made a few years ago has actually accelerated the wear and am afraid to tighten it any more. There doesn't feel like there is any side to side slope but I have yet to test that with a DTI. Is there a standard rule I should be following? I wipe and reoil religiously as many here have advised with way oil.

Thanks in Advance.
Vision is not seeing things as they are, but as they will be.
John Hasler
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Re: Carrige gib adjustments

Post by John Hasler »

I lock the carriage when facing or parting.
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NP317
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Re: Carrige gib adjustments

Post by NP317 »

If your lathe was made with proper materials, the gib should wear while the bed does not.
Gibs are relatively easy to adjust, and eventually replace.
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John Hasler
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Re: Carrige gib adjustments

Post by John Hasler »

The gib is not the only point of contact and in any case the bed always wears.
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Harold_V
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Re: Carrige gib adjustments

Post by Harold_V »

Gibs should be tight to the point where there is (slight) drag at the tightest point of travel. Anything beyond that will result in the loss of travel, and there is nothing to be gained by having the gib looser. If you find your machine is loose in a given area, that is attributed to local wear of the way surface(s), not wear of the gib.

It is beyond being reasonable to assume that only one surface will wear, although it is not unreasonable to assume that one surface can be more resilient than the other. It is far more desirable that a gib be sacrificial. That is accomplished by heat treatment of the ways, which is not commonly found in less than industrial rated machines.

It is not uncommon to find gibs made of steel. In that instance they are usually adjusted by multiple set screws which bear on the length of the gib.

It is well known (and accepted) that gray iron is a good bearing material, even when matched with steel.

H
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pete
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Re: Carrige gib adjustments

Post by pete »

Afaik it's always standard practice to lock the carriage as John mentioned when facing or making critical cuts on any lathe that has a rack and pinion drive for the carriage longitudinal feed since there's nothing other than the carriage weight holding it in position against the cutting forces. That extra rigidity with the carriage locked down further helps to reduce any chatter at the tool point. But tightening any gib too much greatly accelerates wear on the components. On a worn lathe about all you can do is adjust to a compromise condition where the carriage is adjusted as tight as possible on the worn portion of the bed ways yet still allows smooth movement to the less worn areas without being too tight. That assembly that prevents the carriage from lifting doesn't usually wear all that evenly, I'd pull the parts for a check and making new ones might help a bit. It's also a mostly neglected area that gathers old congealed oil and chips so a detailed cleaning might help some as well.
RSG
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Re: Carrige gib adjustments

Post by RSG »

Just got back from Florida, thanks or the notes.

I can lock the ways I suppose, for final facing cuts. It sounds like I better not tighten the gibs anymore then or risk accelerating wear on the front end of the lathe. If feels like there is a very slight amount of resistance so it still feels good.

Guess maybe it's time for a new lathe :)
Vision is not seeing things as they are, but as they will be.
pete
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Re: Carrige gib adjustments

Post by pete »

Replacing with a new one depends on what you currently have. While it can be great deal of work, if the machines original quality was high enough a full bed and slide re grinding can be well worth it because you then know exactly what you have verses possible unknowns with a lower end new machine. If it isn't worth doing so? I've spent more hrs than I'd care to add up looking at various new lathes available today from mainland China and Taiwan that were within what I could spend up to one's way outside my budget. I found there was there is a huge difference in both quality, features and overall machine rigidity that seems to generally start at the 13"- 14" swing size of machine for not a massive difference in price in comparison to the 12" machines. For myself overall machine weight is a problem or that's the direction I would have gone.
RSG
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Joined: Fri Feb 04, 2011 9:59 am
Location: Ontario, Canada

Re: Carrige gib adjustments

Post by RSG »

Thanks Pete!

Resurfacing might be an option, didn't think of that. The lathe I have is a 12x36 King Canada, so not the best, but not the worst either. If I did go with a new lathe it would be as you mention, the most robust I can get and in 14" range. But that's down the road as I don't have the room right now. Once I move to a new shop it will be the first thing I do.
Vision is not seeing things as they are, but as they will be.
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