This morning I screwed a 11" vase held on a faceplate back on my lathe
to re-turn the neck and make it a little less tacky. The unsupported
neck end wobbled quite a bit and I assumed the old axiom or urban myth,
"replaced work is never centered" had got me. This is about _replaced_
work and I understand that blanks originally misaligned on a faceplate
can be turned to round. Like woodturners, faceplates need not be perfect
to be useful.

The spindle and faceplate threads had looked ok so I hadn't cleaned
them. I took a closer look and there it was, a smashed miniscule chip.
I mean just a meer wisp. This time I cleaned the threads and now there
was almost no wobble.

I decided to clock by eyeball the runout along a 2 X 10 maple cylinder
made as smooth and accurate as I could turn it. It was held on a clean
good quality face plate without tail support. Not the accurate
precisely controlled (except for oversight) govt. grant experiment with
stipend, travel and meal allowances, but good enough for a NASA
subcontractor or this 'shadetree scientist'. Certainly not the
contribution to mankind like the study that proved overeating makes you
fat.

I digress, but anyway the blank ran quite concentrically at the spindle
and with no significant runout as I looked along the shaft. Then I
interposed various bits of debris, shavings, pieces of thread, washers
that weren't machined spacers, even a bit of dried varnish. Turns out I
didn't need to be funded by a govt. grant for a dial indicator electron
microscope to see the runout as I neared the blank's end. It was clearly
visible and significant. (however I could have used the prestige,
stipend and the meal & travel allowances)

What I'm trying to say in as many words as possible is, "Don't assume
that your lathe's spindle and fixings threads are clean". Wipe them each
time. An unseen wisp of debris makes a wobble that will increase as the
blank is longer. It's worse than some of you may think.


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

"Arch" wrote: (clip) An unseen wisp of debris makes a wobble that will
increase as the blank is longer. It's worse than some of you may think.
^^^^^^^^^^^^^^^^
This is one of those obvious-after-it's-pointed-out facts. Thanks for
pointing it out.

So a bit of flakiness results in being off-center? I have been accused of
that all my life. It's nice to know it can be more universally applied to
woodturning, as well. -mike

Hi Arch

Yes Arch and this also applies to other things, for instance, drilling
a to be accurate deeper hole with your drill press, and it seems to
have gone off kilter, first thing people blame is the drill bit (people
assume the table is at 90 degrees) you'd be surprised how far a bit
goes off with the table just a tad out of 90 degrees or the table not
clamped tight, check it out you'll be surprised.

Seems like every time I got into trouble was the time I assumed
something or other.

Have fun and take care
Leo Van Der Loo

Arch wrote:
This morning I screwed a 11" vase held on a faceplate back on my lathe
to re-turn the neck and make it a little less tacky. The unsupported
neck end wobbled quite a bit and I assumed

/SNIP/

What I'm trying to say in as many words as possible is, "Don't assume
that your lathe's spindle and fixings threads are clean".

/Snip/

Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

wrote: (clip) Seems like every time I got into
trouble was the time I assumed something or other.
^^^^^^^^^^^^^^^^
The countless assumptions you make every day that don't get you into trouble
go unnoticed. :-)

Tedious, indeed.

Must you?

J.

Hi J.
Probably not.


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings