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06-17-2019, 04:46 PM

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Originally Posted by CESSNA10 View Post
The guys who installed my Brunswick glenwood spent an 2 hours installing and another
hour leveling. They had a 6 small levels all over the table, kept moving them and shimming. Trust me it was level when they finished and a year later is still level
That's kind of my point, when leveling the slates on a pool table, there's more to it than just leveling side to side and end to end. When the slates are crowned or swayback, that throws in a whole different approach to leveling the slates. You can level a pool table until you think its perfect, then scratch your head trying to figure out why the balls roll away from the long rails at one end of the table, but not the other end. Or they roll towards the end rails halfway down the table, but roll dead straight down the middle.
  
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06-17-2019, 05:35 PM

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Originally Posted by Bob Jewett View Post
The company I used to work for makes a laser measurement system (Keysight 5530 Dynamic Calibrator) that can measure flatness to 10 microinches over the surface of a pool table. That appears to be a lot better than the Starrett granite plate. If you are really interested, the manual for the HP 5528A has a good explanation of both how the general system works and the details of flatness measurement. The manuals or data sheets of both systems are available on-line. (If you already understand laser interferometry the manuals will make more sense.)


  
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06-17-2019, 09:21 PM

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Originally Posted by CESSNA10 View Post
The guys who installed my Brunswick glenwood spent an 2 hours installing and another
hour leveling. They had a 6 small levels all over the table, kept moving them and shimming. Trust me it was level when they finished and a year later is still level
Did they also super glue the slate seams so they won't separate?
  
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06-17-2019, 09:23 PM

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Originally Posted by CESSNA10 View Post
The guys who installed my Brunswick glenwood spent an 2 hours installing and another
hour leveling. They had a 6 small levels all over the table, kept moving them and shimming. Trust me it was level when they finished and a year later is still level
Second question, what is the cloth on the table.
  
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06-18-2019, 03:57 AM

Quote:
Originally Posted by Bob Jewett View Post
The company I used to work for makes a laser measurement system (Keysight 5530 Dynamic Calibrator) that can measure flatness to 10 microinches over the surface of a pool table. That appears to be a lot better than the Starrett granite plate. If you are really interested, the manual for the HP 5528A has a good explanation of both how the general system works and the details of flatness measurement. The manuals or data sheets of both systems are available on-line. (If you already understand laser interferometry the manuals will make more sense.)
Did some quick reading and the thought dawned on me that I have this wrong regarding leveling a granite surface. I'm thinking now that the surface is the Standard in this case and the measuring device only needs to be within tolerance of the work being done.

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.
  
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06-18-2019, 04:02 AM

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Originally Posted by realkingcobra View Post
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.

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06-18-2019, 04:38 AM

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06-18-2019, 06:40 AM

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Originally Posted by logical View Post
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.
  
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Bob Jewett
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06-18-2019, 11:13 AM

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Originally Posted by 3kushn View Post
... 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]


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06-18-2019, 12:42 PM

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Originally Posted by 3kushn View Post
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...hnical-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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06-18-2019, 12:45 PM

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Originally Posted by Bob Jewett View Post
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.
  
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06-18-2019, 12:48 PM

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Originally Posted by realkingcobra View Post
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.


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06-18-2019, 12:49 PM

Until someone can prove all these suggested theories about how to level slates, all they'll ever be is untested theories.
  
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06-18-2019, 12:52 PM

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the conversation evolved past pool table slates to much more precise metrology

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.
  
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06-18-2019, 12:57 PM

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Originally Posted by realkingcobra View Post
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.

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.


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