So tell me about laser markers/levels

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?
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Red Green wrote:

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.
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Pete C. wrote: ...

Precisely--the accuracy is in making the mounting precise and the ability to level the unit itself accurately. The cost is in the machining and other manufacturing to get precision and accuracy there. The whole device relies upon base leveling and that essentially boils down to the equivalent of a spirit level--it costs bucks to get the precision required to translate from +/- some relatively small number over 100-ft, say, to the equivalent over the few inches at most of the length of the base. The laser itself is the almost trivial part--straightline propogation of the light beam comes for virtually nothing comparatively.
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If you need a Laser level, retire or get glasses. That crap is a gimmic for the gulible.
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It would sure be interesting to see YOU accomplish floor flatness requirements or install a drop ceiling in a Wal-Mart or similar competitively without a laser.
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On Fri, 06 Mar 2009 07:48:27 -0600, DanG wrote:

LOL I've been doing suspended ceilings for twenty years or so and the first lasers we used (big things with a spinning beam) were super expensive- sometimes costing thousands of pounds. Previously we used to get by using water levels.
A water level can be infinitely more accurate than a badly zeroed laser.
Although nowadays I use a DeWalt DW087K I got brand new from the States a year or so ago. The best $130 (equivalent GBP amount) I've ever spent (or should I say 'invested), it's paid for itself many times over in that time.
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They work great, if you're not too stupid to use them. -----
- gpsman
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LOL! <snicker>
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wrote:

Done at age 48

Done that one too.

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My favorite is a PLS5 by Pacific Laser Systems. Used it to frame in a 4 over 12 roof replacing a 1 " in 20' shed roof that leaked badly. The self leveling is great, makes set up quick and easy. Before that it was a Harbor Freight $30 kit on a tripod, and even that was good for getting the wainscot heights perfect in several rooms. Checked the PLS5 once with a plastic tubing and water level rig and it was dead on. Some the spec variations are due to the spot size, but its easy to mark the center of the spot for good accuracy. For working outdoors more elaborate setups with laser detectors are essential. Watch a survey crew next time you are near one...they have the most sophisticated gear of all. Even old fashioned farm drainage contractors and excavating outfits would never go back to older methods.
Joe
Joe
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