Red Green wrote:

So many times I could have used one. Everyday light duty B&D drill has
one built in. It can and has been handy. But I'd like to get a decent
one. Trouble is, even the ones that push say $75 (I know they can cost
hundreds) have an accuracy spec I think sucks for a laser. If I recall,
lasers are coherent light and are pretty darn straight. Light travels
straight unless it's bent or distorted and laser light doesn't disburse
in general. Also if I recall, the intensity and directness of laser light
depends a lot on the mirrors generating the exit beam.

How the hell did I get off on that tangent...?

Anyway, I see accuracy of +/- like 1/2" in 100'. Saw a $35 Sears brand
one today (not self leveling) that was +/- 1/2" in 30 ft. Crimus!, I can
almost do better than that eyeballing.

What exactly is the "accuracy" spec?

For a self leveling one, does this mean the two endpoints at the spec
distance and be off up or down by 1/2"?

How about one that is not self leveling...basically shooting a straight
line. Does it mean the beam can be bowed +/- 1/2" at any point alone the
line?

The specs are related to the quality of the bubble levels used in the
units, the quality of the factory alignment of the mirror or laser
mount, etc., not the laser beam itself. The laser beam will spread a bit
with distance, giving a larger spot size because the beams from laser
diodes aren't as well collimated as those from other types of lasers.