Millrite cuts in one direction only


Another chapter in the unfolding saga of my education as a machine tool tech.
While using the Millrite MVI to mill the ends of mild steel bars off square, I
noticed something odd. When moving the table in and out in the Y direction
(closer and farther from the column) with the table clamped in the X-axis
direction, cutting would happen only in the conventional-milling direction, and
no cutting would happen in the climb-milling direction, unless I moved the table
in the X-direction (side-to-side).
The bar is held in a milling vise, the bar being parallel to the T-slots in the
table, with the left end being presented to the side of the cutter (6 helical
flutes, 1" in diameter).
As I'm cranking the table in and out I'm wondering what could cause that.
Clearly, there is some unintended X-axis motion due to the intended Y-axis
motion, despite the X-axis being clamped. So, I used the Skoal optical
centering scope to test the
theory, finding that reversing Y-axis direction causes a ~0.0028" X-axis motion.

That's a lot, and certainly explains why the mill would cut only in one
direction, and also why I had some difficulty cutting the bars to a specified
length.
Cause? The Y-axis feedscrew is on the right side of the saddle, so if the
saddle-to-knee gib is loose the saddle will cock one way when being cranked
closer to the column and will cock the other way when being cranked away from
the column. So, time to adjust the saddle-knee gib. This was easily done, and
eliminated the X-axis motion due to Y-axis motion. I wonder when that gib was
last tightened.
What I have not yet done is to tighten the table-saddle (X-axis) gib, as this
requires removal of the table-saddle assembly from the mill to get access to the
adjustment screws and setscrews. Given the difficulty, I bet this gib has never
been adjusted. The X-axis feedscrew is in the center, so cocking would be more
random and thus more confusing than in the Y-axis. Table removal isn't
difficult, but requires a small hoist. I don't have the space to store such a
hoist, but they can be rented from the local Taylor Rentals place.
Or, I can hang the table from the ram with welded-link chain and quick links
and
eyebolts bolted to the table, undo and remove the saddle-knee gib, and crank the
knee down leaving the table-saddle assembly dangling from the ram. Perhaps I
can then tighten the table-saddle gib on the dangling assembly. I'll have to
work out the details of how this would be done safely. And the Y-axis DRO will
have to be removed. I already have the eyebolts and matching thick washers and
T-nuts, bought precisely to allow secure attachment for safe lifting of the
table.
Joe Gwinn
Reply to
Joseph Gwinn
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Joseph Gwinn fired this volley in news: snipped-for-privacy@news.giganews.com:
Not for nothin', Joe, but checking the gibs is normally a weekly cleanup/lubrication task.
I normally expect after one (not over-fed) cut in either direction to pull swarf in the other.
LLoyd
Reply to
Lloyd E. Sponenburgh
Yep, but I don't think people really do it weekly.
Especially, the table-saddle gib, which is quite inaccessible.
Yes, and the fact that this didn't work is what got me looking.
Joe Gwinn
Reply to
Joseph Gwinn
No, I bought it used. It was made in 1965, and looks it.
No, but I did see and hear it run before buying it.
I have been incrementally repairing things, with periodic reports to RCM documenting my progress in learning both machining and machine tool repair. The big problem has been things frozen by lumps of spooge. As time permits, I take something apart and clean it, lubricate it, then reassemble it.
Having never owned a machine tool before, I would be loath to do this all in one go, even if I had the time.
I also added an X,Y, Z (quill) DRO, which is a great help.
The Millrite has no oiling system save the user with oilgun in hand. So far, spooge removal has sufficed, and I have not had to replace anything.
Joe Gwinn
Reply to
Joseph Gwinn
Joe,
Did you buy it new? If not, did you do a tear down to inspect it?
My Bridgeport needed the oiling system repaired, a bit of shim on the knee gib, and a new Y screw and split nut to get it up to usefull status. The Y screw failed due to a blocked oiler.
Wes
Reply to
Wes

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