Adjusting and squaring a 1965 Millrite MVI

Another report from the field:
When I first got the vertical mill in November 2006, I trammed it, and
all seemed well. But I soon started to notice little symptoms of a
non-perpendicular spindle, like the fly cutter cutting in two steps if
the work moved left-to-right, and only one larger step if the work moved
the other way.
I also noticed that the spindle seemed to have considerable runout,
especially angular wobble, but this varied with what R8-shanked tool or
collet or chuck was mounted. Very strange.
I had to shorten the drawbar by about 1/4" so it wouldn't bottom out on
my brand new 1" stub arbor for tools for a horizontal mil, and while I
had the head tilted horizontal to remove the bar, I inspected the inside
of the mill's spindle, the R8 socket. The taper part wasn't smooth,
between 40 years of battering while inserting collets and shanks, and
some tightly adhering hard spooge. Cleaned it off with acetone and a
half-round swiss file, so it's now smooth the the finger. This helped a
lot, cutting the wobble in half or so. But didn't solve the wobble.
Most of the big problems seemed to involve the 1/2" R8 collet, so I
looked at it closely. It has had a long service life, with damage here
and there, but nothing that could cause the observed wobble, something
like 0.006" peak to peak at 5" from the face of the collet. Then I
noticed that the bore of the collet had two sections, fore and aft,
separated by a little groove, and the diameters were not exactly the
same, the front section being slightly larger. Huh? Looked at all the
other collets - only one section, and one diameter, as one would have
expected.
Now the 1/2 inch collet gets by far the most use, so I bought a new
US-made (Lyndex) collet. What a difference. Now the wobble is more
like 0.0005", a tenth as much. Bingo!
I'm wondering if the 1/2" collet I had was a soft collet that had been
machined to fit something special. Anyway, it is now retired.
Now, it was time to re-tram the mill. (This was done with the
now-retired collet, but it shouldn't matter.) I trammed it to less than
0.001" offset in about 15" along the table (X-axis). So far so good.
Then I measured front to back (Y-axis) - it was off by 0.010" in ~7".
Ouch! Perhaps the knee is loose.
Tightened the knee locks, observing the effect with a knife-edge square
between the vertical dovetail on the machine base and the horizontal
dovetail on the top of the knee. Not perpendicular when unlocked,
closes up and becomes almost square when knee gib locks are tightened
hard. The gap at the top looks to be about 0.010". Hmm. Time to
tighten the knee gib adjuster screws.
All the gib adjusters have their jamnut glued to the hex-socket setscrew
adjuster with hard-caked spooge, perhaps decades worth. Take them out
one by one, clean, oil, reinsert, and tighten. Cleaning required
scraping the spooge out of the threads with a 3/8-16 tap and die, and
acetone. Scrape excess paint out of the spot-faced bearing area for the
jamnuts.
Now the knee tilt is within original spec, but I may have it a bit too
tight, as the knee doesn't come down smoothly, instead lurching. Going
up is smooth.
Next weekend, I will re-tram the mill, using the new 1/2" collet and a
well-clamped knee and table. As well as a few bits of hardware I bought
for rigidly attaching dial test indicator to spindle.
I recall a year or two ago someone on rec.crafts.metalworking saying
that with Chinese machine tools, one needed to spend ~40 hours taking
the tool apart, cleaning all the swarf out, finishing the machining, and
adjusting. I believe that may be true, but it's turning out that the
old iron is requiring the same thing and taking about the same amount of
time. The difference is the machine one ends up with.
Joe Gwinn
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Joseph Gwinn
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