On Wed, 27 Jul 2005 19:07:08 -0400, john
wrote:



Harold and Susan Vordos wrote:
wrote in message
ups.com...

The indicator base was placed on the column in order to eliminate any
possible movement of the wheelhead. The measurement does therefore
confirm the flatness of the table which translates into the
straightness of the ways.


No, it does not. No more than running an indicator along a mill table
confirms the squareness of the mill head. Look at it this way. If your
wheel is fixed (which it is) and the table rises and falls, the surface is
ground in a corresponding pattern, therefore yielding what appears to be a
surface that is flat. When you run an indicator on the table, all it's
telling you is how faithfully the wheel has followed the pattern, the ways.
It may or may not be flat, and most likely is not, especially if you're
using an older machine. . You can't check flatness that way--it should be
done by comparing on a surface plate of known flatness. Only then can you
discern the rise and fall of the surface, which then translates into
flatness.

Harold





Just use a precision level. Shim it up so the bubble is in the center
and run the table back and forth. IF its going back and forth over the
mountain of unworn metal of the ways in the middle of the travel you
will see the bubble go back and forth as you run the table left and
right. A cheap and dirty way to tell is with a laser pointer and a
mirror. Put the mirror on the middle of the table mounted upright and
aiming along the table, Clamp the laser pointer so it hits the mirror
and bounces off to a far wall. Now all you got to know is a little trig.


John


The laser pointer method can be extraordinarily sensitive but
use TWO mirrors setup to be almost parallel.

Fire the fixed laser pointer beam so that it zigzags several
times between the two mirrors finally finishing off the end to land on
any convenient white card scale.

One mirror is fixed to the test surface and the second mirror
anchored to a fixed location. The angular sensitivity doubles at each
reflection so it doesn't need many reflections to reach scary
sensitivity!

Surface silvered mirrors give the best results but ordinary
vanity mirrors are usable if you are content with a few reflections.
Old hard disk platters are also usable but don't try to cut them - it
destroys the flatness.

The mirrors need to be a long way apart so that the zig zag
angle is small and the beams do not move beyond the limits of the
mirror surface as the table is traversed. There will a small movement
in spot position in the direction of the zigzag angle as the table is
traversed so the measurement must be made at right angles to this
direction i.e for up and down angular measurement the zig zag path
should be horizontal.

Jim