On 2009-12-18, Richard J Kinch wrote:
Charles U Farley writes:

I read somewhere (HSM probably) Someone drew a
plumb line on the wall opposite the mill. They had a laser pointer
mounted on the mill head with the laser dot pointed to the line. When
the head was moved the alignment was good as long as the dot remained
on the plumb line on the wall (and the mill level). It's suprisingly
accurate if you do the math.

This laser alignment idea is someone's ill-conceived fantasy. You don't
get any accuracy without projecting the spot a long distance. But laser
pointer spots are big blobs over such a distance (many thousandths), so
there's no accuracy to eyeballing a blob onto a plumb line.

A) You can reduce the size of the dot with a tiny hole in a thin
metal plate. (Also the brightness.)

B) Consider that the spindle is perhaps 8" away from the column
(not too unlikely, given the size of the machines which
typically have round columns).

Assuming that the wall is perhaps five feet from the column
(60") then 0.001" at the spindle becomes 0.060" at the wall.
(And five feet to the wall behind the operator is not that
unreasonable, especially if there is another machine tool, such
as a lathe, on the other side of the aisle.

Enjoy,
DoN.

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