"Bill Schwab" wrote in message
nk.net...
snip----
I remember cautions about
the relatively large area of blur that is in fact a serious injury
waiting to happen, and some mention of a guy named "Lefty". While I
suspect that particular "Lefty" was largely a mythical figure, I note
that myths are often based in truth if not fact.

Chuckle!

Yeah, they're quite intimidating, but when applied properly, they're no more
dangerous than other cutters. One learns to keep hands away----and
always point your acid brush such that it can't be pushed into your hand.

It's dead easy to determine how much shimming you need. Spin a DTI on
the
table of the mill, mounted in the spindle in a drill chuck, so you have
something to grip. The indicator should be mounted such that it
generates
a circle the same size as the mounting boss at the base of the column.
That will reveal not only where you must shim, but how much.

When you put it that way, it does sound easy. The holes appear to be at
about 4.5x9 inches on center. The 4.5 in gap (if that's really what it
is) just barely fits between the slots (on the table vs. "in" the
slots). Or should I use the outside dimensions of the flange? The
inside dimension seems most appropriate, but I'm not sure I want to
spend that much time under 700 lbs of metal that is dangling on a nylon
sling.

The information you are looking for is how much it will take to tilt the
column until it is at right angles to the table-----which would likely best
be checked at the point of the bolts. I get the idea that the bolts you
speak of are not spaced @ 90 degrees, so determine the bolt circle, and
swing the indicator in that arc.

You want the indicator to make contact on the front and back of the table,
and at each side @ 90 degrees. If you find the T slots are roughly the
same spacing as the circle you must spin (the bolt circle of the base of the
column), move the saddle until the circle permits contact of the indicator
when it's on each side of center.

You shouldn't have to lift the head off the machine. Just break the bolts
loose (don't take them out if possible)and tip the head slightly, so you can
insure everything is clean under the flange, tipping once left and once
right, then tighten the bolts again and check with the indicator.
Hopefully you understand that once you touch the indicator to the table, you
don't move the quill. Lock it so it can't move, then rotate the spindle.
What you want to see is how much variation there is from dead true, which is
the condition you hope to achieve. Depending on the quality of your
indicator, this can be troublesome. Lots of indicators don't enjoy being
rotated across slots, so if you can make a setup whereby your indicator
trails off instead of approaches the slots sideways, that's the best way to
go. Don't preload the indicator by much, so it doesn't have to move far
before the ball is on the table as it crosses the slots. Rotate by hand,
slowly.

Should I use any particular torque when replacing the bolts, or just
give a reasonable yank on an appropriate wrench?

Once you've shimmed the base, tighten the bolts well, then check again with
your indicator. While everything should change according to the amount of
shimming you do, things like this have a way of coming out somewhat
differently than you planned. Don't quit until you have a variation on your
indicator of less than a thou. Shoot for dead nuts.

I have no idea about torque specs, but once you have the flange well
tightened, any further tightening shouldn't affect your indicator reading.
If it does, something isn't right. When you're finished, make sure the
bolts are well tightened. Use good sense----tighten them, but don't try to
break them. Remember, the forces of the cuts you make are transmitted
through these bolts, and you don't want any movement.

Install the
appropriate amount of shim to establish a 0-0 reading in all positions.
You
may have to use small strips @ 90 degree intervals to get it right. I
think you get the idea.

I think so, except for the 90 degrees part. I am thinking of splurging
on slotted SS shims, but will want to make at least a first measurement
to get an idea of how much material I will need. I suspect it's not
much, but might be surprised.

What you're likely to discover is that you need different thicknesses for
each position. If you use .001" shim stock and stack it, you would probably
have all you needed to get the job done. No need to buy various
thicknesses. You should be able to cut shims with scissors that are maybe
an inch wide that have a slot for the bolt and will slip under each bolt
position to raise it. One, the lowest point on the indicator (hopefully at
one of the bolt positions), can be your reference point, and won't need to
be shimmed. The other three positions (where your bolts are) will each
likely need a shim of different thickness. That's what your indicator will
tell you-----how much-------and where.

Thanks!

Bill

Welcome.

Let us know how it turns out.

Harold