How level is "level" for pool tables?

logical

Loose Rack
Silver Member
In fact, I bet I could give all of you a chance to figure out how to level the slates in some of the situations I've had to deal with, and not one of you giving advice on how to level slates....would figure out how to correctly level them.
I am sure the various conditions that you find frames and slates in presents some unique challenges. Nobody doubts you could do it faster than most and better than all. But given a basic Gold Crown in good condition it is no rocket surgery to get it level, planar, flat, smooth and stable enough to play well for many years.

I see more sloppy work on how people set up rails than issues with slate.

Sent from my SM-G950U using Tapatalk
 

realkingcobra

Well-known member
Silver Member
I am sure the various conditions that you find frames and slates in presents some unique challenges. Nobody doubts you could do it faster than most and better than all. But given a basic Gold Crown in good condition it is no rocket surgery to get it level, planar, flat, smooth and stable enough to play well for many years.

I see more sloppy work on how people set up rails than issues with slate.

Sent from my SM-G950U using Tapatalk

I've seen to many GC frames that were the reason the slates were crowned or swayback just by mounting the slates to the frames.
 

Bob Jewett

AZB Osmium Member
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... Sticking my toe into the black hole.... How is the calibration laser equipment calibrated and how is that calibrated, and that.........?? In torque and force they stop at physical weights in a controlled room on a precision arm, calibrated to a specific GPS location. Even this isn't without error. Friction & motion in the arm and calibrating the scales that weigh the weights.
There is a great deal of information available on-line about physical standards and calibration techniques. Many clever people have been working on developing the techniques for hundreds of years. There is much to know.

Laser-based precision measurement techniques use optical interferometry. That allows distances to be measured down to a fraction of a wavelength of light. A wavelength of visible light is about 0.5 microns or 20 microinches.

Really accurate laser distance systems are calibrated for the speed of light in the local air since wavelengths go down as the speed goes down. If you know the frequency you know the wavelength and it is possible to measure the frequencies of laser light to about 15 places.

You have probably heard of "atomic clocks" that are very accurate. In fact the standard of time and frequency is a very precise resonance in cesium atoms and time and frequency are now defined in terms of that cesium resonance. The accuracy of such systems allows GPS among other things. A GPS receiver can know the correct time to within 20 billionths of a second because it is talking to multiple atomic clocks on multiple satellites.

For about 20 years (until the 1940s) a special pendulum clock was the standard of time measurement. Here is some info on that:

In 1984 Pierre Boucheron studied the accuracy of a Shortt clock preserved at the US Naval Observatory.[3][18] Using modern optical sensors which detected the precise time of passage of the pendulum without disturbing it, he compared its rate to an atomic clock for a month. He found that it was stable to 200 microseconds per day (2.31 ppb), equivalent to an error rate of one second in 12 years, far more accurate than the 1 second per year that was previously measured. His data revealed the clock was so sensitive it was detecting the slight changes in gravity due to tidal distortions in the solid Earth caused by the gravity of the Sun and Moon.[19]
 

DaveK

Still crazy after all these years
Silver Member
Wonder how "overpriced" Starrett gets within these specs on their granite surfaces?
How do you measure this? Your $20K laser isn't good enough unless my feeble math is working.

Laboratory Grade AA = (40 + diagonal squared/25) x .000001" (unilateral)
Inspection Grade A = Laboratory Grade AA x 2
Tool Room Grade B = Laboratory Grade AA x 4.

So $20K laser can't come close to checking a Starrett granite surface.

Sorry, just intrigued with Precision and how its done.

One way to measure flatness is using "optical flats". Here is a reasonable explanation of how they work :

https://www.kemet.co.uk/blog/lapping/how-to-measure-flatness-technical-article

I believe that optical flats are ground similar to how glass lenses are ground. Then it becomes an issue of testing the flatness of an optical flat, and again optical methods are used (Fizeau interferometry for example).

Surface plate measurement using really sensitive dial gages :

http://www.tru-stone.com/pages/smp.asp#prod

Fascinating stuff IMO.

Dave <-- owner of an 8" x 12" surface plate and is in the process of making a spherometer using a 0.0001" dial gage
 
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realkingcobra

Well-known member
Silver Member
There is a great deal of information available on-line about physical standards and calibration techniques. Many clever people have been working on developing the techniques for hundreds of years. There is much to know.

Laser-based precision measurement techniques use optical interferometry. That allows distances to be measured down to a fraction of a wavelength of light. A wavelength of visible light is about 0.5 microns or 20 microinches.

Really accurate laser distance systems are calibrated for the speed of light in the local air since wavelengths go down as the speed goes down. If you know the frequency you know the wavelength and it is possible to measure the frequencies of laser light to about 15 places.

You have probably heard of "atomic clocks" that are very accurate. In fact the standard of time and frequency is a very precise resonance in cesium atoms and time and frequency are now defined in terms of that cesium resonance. The accuracy of such systems allows GPS among other things. A GPS receiver can know the correct time to within 20 billionths of a second because it is talking to multiple atomic clocks on multiple satellites.

For about 20 years (until the 1940s) a special pendulum clock was the standard of time measurement. Here is some info on that:

In 1984 Pierre Boucheron studied the accuracy of a Shortt clock preserved at the US Naval Observatory.[3][18] Using modern optical sensors which detected the precise time of passage of the pendulum without disturbing it, he compared its rate to an atomic clock for a month. He found that it was stable to 200 microseconds per day (2.31 ppb), equivalent to an error rate of one second in 12 years, far more accurate than the 1 second per year that was previously measured. His data revealed the clock was so sensitive it was detecting the slight changes in gravity due to tidal distortions in the solid Earth caused by the gravity of the Sun and Moon.[19]

When slate is ground to the industry standard of +/- 10,000ths of an inch flat, and even still, slate is flexible, carpeting compresses, floor joists move....how is any lazor can any lazor leveling system be more accurate than a starrett 8" level, and ANYWHERE near time effecent since leveling pool tables don't pay by the hour. There is no way in hell a lazor leveling system is going to compensate for a floor that moves while you're walking around the pool table reading the level of the slate. And here's another problem with the lazor leveling system....constantly going back over areas of the slate that you already brought up to level, but then changed because you raised the level of the slate somewhere else, changing everything you already thought you had level.

My comparison of your lazor leveling system would be like looking through a telescope at the moon, can see it clearly, but looking at a poster on the wall 10' away, nothing is visible, because it's not designed to see something 10' away. Lazor leveling systems were not designed to level pool tables, therefore can not do the job as well, nor as efficient as a Starrett or any other quality machinist level.
 

DaveK

Still crazy after all these years
Silver Member
When slate is ground to the industry standard of +/- 10,000ths of an inch flat, and even still, slate is flexible, carpeting compresses, floor joists move....how is any lazor can any lazor leveling system be more accurate than a starrett 8" level, and ANYWHERE near time effecent since leveling pool tables don't pay by the hour. There is no way in hell a lazor leveling system is going to compensate for a floor that moves while you're walking around the pool table reading the level of the slate. And here's another problem with the lazor leveling system....constantly going back over areas of the slate that you already brought up to level, but then changed because you raised the level of the slate somewhere else, changing everything you already thought you had level.

My comparison of your lazor leveling system would be like looking through a telescope at the moon, can see it clearly, but looking at a poster on the wall 10' away, nothing is visible, because it's not designed to see something 10' away. Lazor leveling systems were not designed to level pool tables, therefore can not do the job as well, nor as efficient as a Starrett or any other quality machinist level.

:lol: :lol:

Dave
 
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realkingcobra

Well-known member
Silver Member
Until someone can prove all these suggested theories about how to level slates, all they'll ever be is untested theories.
 

realkingcobra

Well-known member
Silver Member
:lol: the conversation evolved past pool table slates to much more precise metrology :lol:

Dave

Then this thread belongs in the NPR forums, because none of these theories about the relativity of flatness pertain to leveling pool tables, because none of them can be of practical use on todays pool table leveling.
 

Bob Jewett

AZB Osmium Member
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Until someone can prove all these suggested theories about how to level slates, all they'll ever be is untested theories.
So.... You don't think every Valley table installation should be required to use a $40,000 flatness system and the slate must be level to 20 microinches? Personally, I think that would be a good idea.:wink:

On a slate-related topic -- rather than hatred of Valley tables -- some carom tables grind the top corners of the slates so sharp that no fill material is used. The corners are sharp enough that you can cut yourself on them.
 

Bob Jewett

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Then this thread belongs in the NPR forums, because none of these theories about the relativity of flatness pertain to leveling pool tables, because none of them can be of practical use on today's pool table leveling.
But think of tomorrow! I can imagine an automated system that could level a table to a few thousandths in five minutes. Even more interesting would be a system that could map out the topography of a table. The laser-based system I mentioned above is used to do just that but with far more accuracy than needed, of course. What if you could give a customer a contour map of their table in less than 10 minutes to show how badly the previous mechanic had done? Then you could show them what it takes to make it right.
 

DaveK

Still crazy after all these years
Silver Member
Then this thread belongs in the NPR forums, because none of these theories about the relativity of flatness pertain to leveling pool tables, because none of them can be of practical use on todays pool table leveling.

Threads meander :shrug:

Dave
 

kevoka

AzB Silver Member
Silver Member
Even more interesting would be a system that could map out the topography of a table.

What if you could give a customer a contour map of their table in less than 10 minutes to show how badly the previous mechanic had done?

Interestingly enough, the bar I hang around had a regular who is a surveyor and had a very high laser surveying tool in his truck.

We got the crazy idea to map out the topology of the bar's Alltech 8x4 table down to roughly the in.sq. grid level.

3 hours and many beers later we had about 1/4 of the table done when someone mentioned the topology map would only be valuable until some 300 lb. dude stretched across the table for the long shot, and stressed the frame and slate joints.

10 minutes would make it worthwhile.....12 hours not so much.
 

realkingcobra

Well-known member
Silver Member
So.... You don't think every Valley table installation should be required to use a $40,000 flatness system and the slate must be level to 20 microinches? Personally, I think that would be a good idea.:wink:

On a slate-related topic -- rather than hatred of Valley tables -- some carom tables grind the top corners of the slates so sharp that no fill material is used. The corners are sharp enough that you can cut yourself on them.
Bob, if you knew anything about the Valley tables, then you'd know the slate just lays to the frame of the table...if the cabinet is swayback, then the slate lays swayback....its not the slate, it's the cabinet, and there's no way the slate can be shimmed up to level end to end....because then you can't bolt the rails on, they follow the flatness of the slate while the cabinet sinks in the middle!!
 

realkingcobra

Well-known member
Silver Member
But think of tomorrow! I can imagine an automated system that could level a table to a few thousandths in five minutes. Even more interesting would be a system that could map out the topography of a table. The laser-based system I mentioned above is used to do just that but with far more accuracy than needed, of course. What if you could give a customer a contour map of their table in less than 10 minutes to show how badly the previous mechanic had done? Then you could show them what it takes to make it right.

And there's the million dollar question, what would it take to make it right?? Do you happen to have a portable grinding system in your other pocket??
 

realkingcobra

Well-known member
Silver Member
But think of tomorrow! I can imagine an automated system that could level a table to a few thousandths in five minutes. Even more interesting would be a system that could map out the topography of a table. The laser-based system I mentioned above is used to do just that but with far more accuracy than needed, of course. What if you could give a customer a contour map of their table in less than 10 minutes to show how badly the previous mechanic had done? Then you could show them what it takes to make it right.

I once worked on a GC3 that the previous mechanic determined that the nose of the cushions were.to low which is why the balls were hopping off the rails, so his FIX.......was to use a belt sander to grind down the edge of the slate at an angle in order to raise the nose height when the rails were bolted back on....I walked away!!!
 

ShootingArts

Smorg is giving St Peter the 7!
Gold Member
Silver Member
grid

Interestingly enough, the bar I hang around had a regular who is a surveyor and had a very high laser surveying tool in his truck.

We got the crazy idea to map out the topology of the bar's Alltech 8x4 table down to roughly the in.sq. grid level.

3 hours and many beers later we had about 1/4 of the table done when someone mentioned the topology map would only be valuable until some 300 lb. dude stretched across the table for the long shot, and stressed the frame and slate joints.

10 minutes would make it worthwhile.....12 hours not so much.



You could use a six inch grid and still be more accurate than anything done with a level. Also, those readings would be likely to give indications of any problem between them.

The registered surveyor I used in 1995 happened to be a government surveyor as his day job. Their equipment was accurate to 3/8" to the mile back then and I think it is far better now. I think the last commercial tool I saw used eight satellites, I don't know how old it was.

Hu
 

realkingcobra

Well-known member
Silver Member
You could use a six inch grid and still be more accurate than anything done with a level. Also, those readings would be likely to give indications of any problem between them.

The registered surveyor I used in 1995 happened to be a government surveyor as his day job. Their equipment was accurate to 3/8" to the mile back then and I think it is far better now. I think the last commercial tool I saw used eight satellites, I don't know how old it was.

Hu

Anytime you want to put up satellites against my starrett to level a pool table, just let me know...but the pool table has to remain IN the bar....LOL
 

ShootingArts

Smorg is giving St Peter the 7!
Gold Member
Silver Member
not a problem

Anytime you want to put up satellites against my starrett to level a pool table, just let me know...but the pool table has to remain IN the bar....LOL


It can stay in the bar just like that other table stayed indoors. As long as the instrument has a clean shot at the table it doesn't have to be on it or next to it.

You are way out of your depth when you start talking about what lasers or telemetry can't do.

Since less than one in a hundred Starrett levels are used to level pool tables I somehow suspect that isn't what they were designed for. I owned a few thousand dollars worth of Starrett measuring tools from the sixties and seventies before they were stolen. I own a zero to a half inch Starrett mike now that reads in ten-thousandths, cost over a hundred dollars. The Starrett wasn't as accurate as a fifteen dollar chinese piece of crap with an analog dial on it until I sent it back to Starrett. I told them about the chinese mike. To add insult to injury, the chinee mike came in a wooden case, the Starrett in a cardboard box. It cost me another ten dollars for the case! I once owned a Starrett dial indicator that was a thing of beauty. Dropped a hundred on one a few years back, it wasn't any better than the fifteen dollar harbor freight one. Felt like it had sand in the gears!

Starrett was a hell of a fine company fifty years ago. Today, not so much. Harbor Freight was handling a Starrett level. Need I say more?

Hu
 
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