"Jim Wilson" wrote in message
link.net...
Catherine Jo Morgan wrote...
Could a laser level lay a straight
line onto the curved surface, so I could mark it for cutting?

Yes, the "Strait-line" style lasers will work for something like this.

Are the lines or dots always smaller the closer you are?

Yes. Although much narrower than that other light sources, the beams of
these cheap lasers do diverge noticeably. The ones with a finer aperture
have thinner beams. If you can modify one to have a very fine aperture
(I.e, very narrow slit in very thin material), it should be able to do
what you want, within reason. You'll still get a diffraction pattern, but
the main line should be pretty clear for reasonable distance.


Actually that is not true. Those cheap lasers are surprisingly good,
between
1 to 2 mrad divergence. This is the same for ordinary HeNe gas lasers.

You cannot narrow the beam by passing it through a slit. A slit will
cause the beam divergence to increase. The divergence is a function
of the width of the wave front. A narrower wave front (beam with) will
result in a increased divergence. This is a result of wave theory and is
not specific to lasers.

Pete.