On Fri, 29 Jan 2010 07:45:49 -0600, Ignoramus7752
wrote:

On 2010-01-29, Andrew VK3BFA wrote:
On Jan 29, 2:06?pm, Ignoramus2532
wrote:
I bought a "test bar", which is a 10" or so long with MT3 end.

I inserted centers in the headstock and tailstock and mounted the bar
between those. Then I aligned tailstock with headstock, such that the
position of the indicator was the same at both ends.

What you have done is align the test bar between the 2 centres. This
will give you accuracy when your turning between centres, but anything
else, ie chuck work, is unknown. You also need to check the spindle
alignment, preferably first, then align the tailstock. As Robert says,
the (Rollie's Dad's Method) method is good, even if a bit hard to
comprehend at first reading.
(I still need to pull my finger out and correct said measured errors
in my humble 9x20...but need to shift so much stuff to be able to get
access to ALL of the headstock bolts that it aint happened. Yet. But
its on the list).

Guys, thanks. I loathe to adjust the headstock, because I think that I
will make things worse, not better. Why would headstock be misaligned
on this 43 year old lathe? At this point I just want to
measure bed straightness. Anyway, measuring is easy and fun, and is a
harmless activity, so I will just continue on this part. I have a
longer precision ground shaft, but it is not yet center drilled, and I
wanted to do so accurately.

i


The old fashioned method was to mount a piece of stock between centers
and then turn it, full length, with sufficient depth of cut that the
entire diameter was machined. Measure both ends to determine tail
stock offset and adjust. When tail stock alignment is satisfactory
remove faceplate and centers and mount chuck. mount work in chuck with
reasonable overhang and re-machine. Measure head stock misalignment,
if any.

Probably an hour's work; no special test bars needed.

Cheers,

John B.
(johnbslocomatgmaildotcom)