Originally posted by Mudder
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Originally posted by Rifleman1776
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Originally posted by Chuck Key
<br />Even when the points meet exactly, if you rotate the spindle 180 degrees they may not. If not run out.
Originally posted by Rifleman1776
<br />I'm not sure what you mean by the term "run out". If you are referring to correct alignment, the point of a tailstock live center should meet exactly with the point of a drive spur. Anything less than exact is unacceptable.
Agreed, but I think with a wood lathe visually 'exact' would suffice. Some would call it a "sweet spot" when they meet at one point but not another. That is [explitive deleted] nonsense. I was told this by someone who claims to be very knowledgable then checked with many acknowledged master turners. The string of 'explitive deleteds' comments was scorching. There simply is no such thing as a "sweet spot", don't be mislead otherwise. The lathe is true or it isn't. Accessories (mandrels, etc.) that don't meet exactly are defective also.
I’m a little confused by your question.
If you want to measure “runoutâ€, I would define that as how well your mandrel or center runs compared to the centerline of the lathe’s rotational axis. In order to make this kind of measurement you will need a dial indicator or a test indicator and a way to mount it.
First thing I do is see if the mandrel is true by holding the rod in a vee block and setting the indicator to check any deviation from zero at several points along my morris taper.
(that is assuming that you are using a tapered mandrel) Once I am satisfied that my mandrel is running correctly I mount it in the lathe and check the deviation from zero at several places along the mandrel rod.
The other measurement that I take is one of alignment (both vertical and horizontal). I have checked lathes running from the cheapest import up to and including Nova’s, Powermatics and Oneways and I have found that it is possible to **** the tailstock on each and every lathe and throw it out of alignment to one degree or another. Contrary to what Frank says I have found that lathe’s do in fact have a “sweet spot†and this is how I find it.
When I set up to drill I always bring up my tailstock up and while the tailstock is unlocked I bring the point of the drill into contact with the material that I’m drilling while the lathe is spinning and allow it to find center……Also known as the “sweet spotâ€, then I lock tha tailstock and finish drilling. I also do this when I bring the tailstock up to support the end of my mandrel for penturning. The only time that I cannot use this method to find the “sweet spot†is when I’m turning between centers using a spur center in the headstock and in that situation you will be roughing the wood and creatiog your own centerline.
In summation, unless you find that your lathe is GROSSLY out of alignment but does have little runout I would not worry too much because using the methods above you can indeed find that a lathe has a “sweet spotâ€.