How long....?

[Ron LaDow]

I'm looking at the wear patterns on the lathe bed-ways. Where the carriage always is (near the center), the ways show a smooth even pattern. At the ends, where it hardly ever is, the ways show a 'wave' wear pattern that tells me they were never really flat.
It's 20+ years old. The sticker claims 'hardened and ground bed ways'. I work to .0005", 'cause that's as close as I can reliably measure.
How long do I get to keep this thing before it needs straightening (grinding) or replacement? Probably cheaper to replace it, correct?

[MarcF4]

I am looking at a very old machine right now and wondered some of the same myself.

Would you check it with a very good straightedge? Or run a long cut on a small diam(1") aluminum rod and measure with a micrometer to check for variations?

Marc

[Ron LaDow]

MarcF4,
I can only barely see any light under the best straight edge I have. Certainly can't get any feeler gauge material in there. I just turned a bar which was within the .0005" limit at 12" length.
Point is, I think it's fine now. I'm just curious how long it will stay that way.

[SGW]

If you don't abuse it, longer than you need to care about.

See also "Rollie's Dad's Method of Lathe Alignment" at http://people.ne.mediaone.net/wasser/NEMES/RDMLatheAlignment.html

It is *THE* way to set up and/or check a lathe. I described the technique several years ago in an article in (I think) Projects In Metal, but John's description is at least as good if not better than mine.