"DoN. Nichols" wrote in message
...
In article ,
Mike Henry wrote:
I recently set up a used KO Lee S714 surface grinder and was a little
disappointed at the finish, though my experience on these tools leaves a
lot
to be desired. The surface almost seems to have very shallow scallops at
regular intervals. They can't be felt by hand and a fingernail doesn't
catch
anywhere. There is a bit of noise as the grinder winds up but that seems
to
be coming mostly from the motor. The grinder appears to be in otherwise
very good condition.
Hmm ... before we get into the matter of play, I have a some
questions to ask:
1) It the motor original?
I suspect that it is a replacement - it's a GE Stock No. K163 (220 VAC,
3-phase) and looks a lot newer than the grinder.
2) If not, did you replace a three-phase motor with a single-phase
motor?
3) If it still has the original three-phase motor -- how are you
running it?
a) From genuine power company supplied three phase?
b) From a VFD?
c) From a rotary phase converter?
d) From a static phase converter?
Just a home shop here, with single-phase power, so I bought a new Hitachi
L-100 VFD for the grinder.
If your answer is either (2) or (3-d), that could be a source of
your surface finish problem.
I checked the spindle runout with a gage head and amplifier and am seeing
about 0.00075" with the gage tip on the tapered spindle nose (wheel &
collet
were puulled off and belts between spindle and motor were removed).
With the spindle warmed up, or after it has been sitting cold
for a while?
It was checked both cold and after 45 minutes of running with no discernible
difference in the readings.
I
can
also get about 0.0015" deflection in the spindle by manually pushing or
pulling the spindle toward or away from the gage tip.
Is that in the spindle bearings, or in the ways of the vertical
slide? (To tell -- shift the gauge to measure the spindle housing and
repeat the test.
Hmm - hadn't thought of that. Just cecked, though, and only get 0.0002"
deflection when the gauge tip is against the housing.
I think that your measurements may be a bit high -- but the
runout (if it is *consistent* runout, and not slop in the bearings)
would probably be tuned out when you true your wheel with a diamond.
(You *did* true it first, didn't you?)
I'm pretty sure that these readings are not a good sign. KO Lee specs their
new grinders at 0.0001" runout. The wheel was trued before taking the test
grinds. I believe that I fed the wheel about 5-10 thou into the diamond, a
a thou or less per pass, with a couple of passes at the end with no
downfeed.. FWIW, the test grind was made with a couple of tenths downfeed
per pass, with about 0.050" infeed per pass and it was sparked out at the
end.
A friend also suggested that truening the wheel would take out the slop, but
it occurss to me that a bad ball or two (needle?) could cause the wheel turn
just a little eccentrically under load. I'm wondering if that might cause a
slight wheel hop, once per revolution.
The spindle feels
reasonably cool after running for 45 minutes without a wheel or collet
mounted.
Then it at least is probably not too tight --but it might be too
loose.
This seems to be pretty far out of spec to me, but opinions would be
appreciated from those that know better than I.
Another thing to check is whether the pitch of the scallop
matches the teeth of the rack gear on the bottom of the table. If so,
then there is proably some slop in the table ways.
I'll check that out after freshly dressing the wheel again but on the sample
I have now it appears that the pitch of the scallops is about half the pitch
of the rack, maybe less..
If this does need attention, is there any chance that the bearings just
need
adjustment? There's a circular disk threaded into the outboard side of
the
spindle with holes for a pin spanner wrench. I haven't mucked with that
yet
but presume that it's there to adjust bearing pre-load.
It sounds as though it is. I don't know the K.O. Lee grinders,
so I would suggest getting a manual to match *your* machine. (Perhaps
the company can supply this for you, as I believe that they are still in
business.)
Yep, still in business, but they don't seem to have any manuals for this
model although they were happy to send me parts manual. That only has about
5 pages with a couple of sectioned views but not much detail on maintenance
or adjustments. There's virtually no detail on the spindle or bearings.
They did send me a manual for a more recent model (SE612/SE618) but that's
been of no help either.
If the bearings need to be replaced what are the chances of being able to
do
this myslef? A manual for a slightly different KO Lee grinder suggests
that
spindles must be returned to the factory for rebuilding.
I've not tried it. The spindle on my Sanford is still in pretty
good shape -- other than the seals. Oil really flows out of the spindle
bearings at the stone end.
The manual for the Sanford also suggests that if you try to
replace the bearings yourself, instead of sending it to the factory that
you are doomed to disappointment. If so, then I am probably eventually
doomed, as the factory seems to have folded not long after I got my
(very old) grinder.
Well, there is always the option of taking it to a machine rebuilder. I
know of someone somewhat local and might consider that option. I'd like to
be a little more knowledgeable on options before talking to him, though.
Hopefully, others will pitch in with their experience, too.
When I posted, I saw only your question and no followups.
Yours was the first I saw - thanks.
Good Luck,
DoN.
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