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Tailstock alignment

DPittman

DPittman

Ultra Member
So I've been trying to align my tailstock with the spindle with an indicator revolving around the tailstock. Very frustrating process as it seems to wiggle around in not much relation to how I'm adjusting. However, I think I've got it about as close as I am able but I notice there is .0055" difference between the top and the bottom. I've read that height difference isn't critical but I can't find any spec regarding HOW much is acceptable? I'm not making any parts for NASA, but I would like to have precision acceptable for a home machinist. Any thoughts?

Don
 
I think I measured slightly less less than that on mine, but its been a long time. I should re-check. These links discuss a few things of interest & there are likely more on net. I remember freaking out until I did some reading. Check a few things t make sure you are not introducing measurement errors:
- make sure bed & tailstock base perfectly clean, no casting burrs or chips
- ensure consistent tailstock base clamping
- ensure consistent barrel extension & locking
- check the condition of the internal MT bore in tailstock if you are indicating around that. I've seen them ovaled or buggered up on older lathes
- don't put a dowel pin in a tailstock chuck because the chuck is rarely within a few thou unless you have a great one. Best to put a ground MT blank like dead center into the MT bore
- using a gravity sensitive dial indicator can introduce error (plunger reads different pointing up vs. down). So use a good DTI on the most rigid arm setup.
- I've also read not to trust mounting DTI on chuck especially threaded backplate ones because they might not be aligned to true spindle axis depending on how they come in contact when tightened. Although this is a bit of a mind bender to me if its rotating about common axis?
- I always read the same thing, TS always set high at factory as much as 5-thou to allow for wear? But that sure seems like a sh*t load of abrasive sliding would have to occur before you would wear that away to come back to zero?

http://www.chaski.org/homemachinist/viewtopic.php?t=90370
http://www.model-engineer.co.uk/forums/postings.asp?th=106608
 
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