Using a lazer to level slates?

Tomster said:

In the end I bought a Bosch GLL 3-80 - accurate to 0.2mm per meter. So if I place it by the side pocket, the receiver will never be more that 2 metres away from the lazer - max 0.4mm variance, according to the manufacturer specs.

But as mentioned above the thing that the beam shines on is very important as the width of the beam is around 3mm (1/8"). I've tried several different types of receptor material, so far white plastic pipe with a black line around it works ok but suffers from glare. sometimes the black line just dissapears.

I think you need a material that will absorb some of the red light, and make the black line stand out, I also think you need two black lines, one at the top of the beam and one at the bottom to give you better reference. Or possibly something made with projector screen tape that absorbs light, could work.

I undertsand Starrett levels are more accurate, but with the laser if you have multiple receivers you can a quick visual guide to the levelness of the slate that would take a fair bit of figuring out with a Starrett level. So they are useful in a different way, not better.

Click to expand...

There is no doubt laser have their uses. In this particular case I believe a quality machinist level is a far, far better for doing the job of leveling a pool table. How do you verify the accuracy of a laser if you drop it? A level you put on a flat level surface, read it, then simply turn it 180 degrees and read it again to quickly verify accuracy. I use my laser level more as a transit, the level on my laser is for making sure the tool is relatively level or for repeating set up angles. It would require much more effort to shoot that line to different points of a flat surface to check degree of level than just grabbing an accurate machinist level to do the same thing.

Tomster said:

The lazer I bought has a 360 line, so it covers all the table bed. As for accuracy, it's manufactured by Bosch to be within 0.2mm per metere, so 0.6mm across the bed of a table.

http://www.bosch-professional.com/ma/en/line-laser-gll-3-80-p-131496-0601063305.html

If you know how to use a machinest level and are comfortable with it, all good. For me they are fiddly and only show a small part of what's going on with the table at a time, with multiple receivers and a laser lavel you would be able to see what is happening across the whole bed surface immediately.

No harm in kicking the idea around and seeing what comes of it, imho.

Click to expand...

Its not that the accuracy of the laser is in question but rather how easily will you be able to interpret that accuracy by trying to measure a line rather than looking at a bubble. If they are digital receivers that read the measurements it could be done easily but that seems like it could become very costly in a hurry.
i will be interested to see how it works but it would be nice if the results could be compared on the same table to a machinist level.

Tomster said:

Totally agree on both points. It comes down to the receiver/reflector and how easy it is to read, and the end result should be comparable on the same table to a machinist level.

I'll keep kicking ideas around for something that will pick up the line accurately and cheaply, if anybody has any ideas on how to do it please chime in...:smile:

Click to expand...

Here's an idea, just buy a starrett 8" machinist level, try it out, then you'll give up on the laser level completely:thumbup:

realkingcobra said:

Here's an idea, just buy a starrett 8" machinist level, try it out, then you'll give up on the laser level completely:thumbup:

Click to expand...

Agreed.

I do have an extremely accurate lazer, made in America and I purchased it in the 90's.

I could take a Football field size area and it will shoot level to within 1/16".

1/16" will never work for a table.

IF it's all I had, I would place the receiver on the perfect vertical stand just below the lazer line then use playing cards one at a time under the stand until one makes it beep.

Let's say that 5 cards made it beep, go to the other 3 corners and see if 5 cards does the same. If it takes 6 cards, well, figure it out.

Congratulations, you can now go get a Starrett

Tomster said:

Well, actually I did that and tried to follow your instructions but after about 3 hours I was losing the will to live. So I bought out an old Black & Decker Laser level I had kicking around and the slate was level to an acceptable standard (no noticable ball deviation from the intended path) within about 20 minutes.

But I know that my B&D level is not the most accurate and I could maybe do better, so I bought the Bosch GLL 3-80 P which has a 360 beam and is accurate across the playing surface to 1/64" if placed by one of the side pockets.

The only thing stopping this system from being excellent currently is the width of the beam that the laser emits and the ability to pick out a mark within it with the naked eye. If this could be achieved and I'm guessing it's pretty easy when you know how, then the system would be a great way to quickly an easily level a table.

I've attached what I used for the Black & Decker Laser, but the Bosch is significantly brighter, so it produces too much glare/reflection on the white plastic:

So, no need for any more comments on Starretts, but welcome any and all ideas on what type of material to use to pick out the beam as clearly as possible.

Click to expand...

Well, you lasted 2 hours and 59 more minutes than i would have t4ying to use a laser level to level a pool table that's for sure:thumbup:

Tomster said:

So, no need for any more comments on Starretts, but welcome any and all ideas on what type of material to use to pick out the beam as clearly as possible.

Click to expand...

You need to use a flat sheen surface, so that the light is absorbed, instead of reflected. That will make visibility of the beam more clear.

Also, whatever you use should have a flat face, as opposed to the round tube. This is so that the beam is a consistent thickness, that does not vary with distance. If you'll notice, the beam width is much thicker at the centerline of your pvc pipe than it is at the outside edges.

Maybe you could use a flat sheen paint swatch, attached to a rectangular block.

Good luck!

Tomster said:

...but welcome any and all ideas on what type of material to use to pick out the beam as clearly as possible.

Click to expand...

I'm not a mechanic, and don't intend to try to level my own table, but I have worked a bit around lasers and optics....

I think you are inherently limited by the beam accuracy, which is probably produced by a spinning mirror (or something spinning). They are cheap to make but dirt and wear on their spinning parts, temperature, precession... there's a reason you can buy these for tens or a couple hundred dollars but people doing lasers this for serious precision spend thousands or tens of thousands.

We think of lasers as super accurate -- and they are for something like interferometry. But this isn't that -- these are basically fidget spinners inside a box. :smile:

But... to find the center of the beam, consider a pinhole in something thick (need a bit of a tunnel), with a right angle mirror behind so you can see the hole. Mount the pinhole on something you can raise and lower with a fine thread screw. Screw it up until you just barely see the laser, count turns until you stop, divide by two. Move to another place and do the same.

By finding the beam center you offset some issues of beam spread at different distances, and a pinhole can be made almost arbitrarily tiny, you are probably most limited by the accuracy of the screw. Probably some parts off a band saw or other tool that has fine adjustment knobs would be pretty good.

But... there's a reason why these things are pretty cheap for what they do. If you do get something you can count on to detect the beam center, do some tests. Turn the laser off and on, pick it up and put it down, flip it 180 degrees, 90 degrees - see how repeatable your measurements really are.

Thanks for the photo. That looks like a thick light beam. I suspect it's a fast technique, but can't match a Starrett-leveled table.

tjohnson said:

Thanks for the photo. That looks like a thick light beam. I suspect it's a fast technique, but can't match a Starrett-leveled table.

Click to expand...

No laser level made will be nearly as accurate as a starrett 8" level.....period.