Table levelness tolerance for pro events
- Thread starter nataddrho
- Start date
Solution
The WPA equipment specs list flatness requirements. So far as I know, they have never been confirmed at tournaments.
4. SLATES
The thickness must be at least 1 inch [2.54 cm], and the playing surface must be capable, either by its own strength or a combination of its strength and that of the table base frame, of maintaining an overall flatness within + .020 inches [.508 mm] lengthwise and + .010 inches [.254 mm] across the width. Further this surface should have an additional deflection not to exceed .030 inches [.762 mm] when loaded with a concentrated static force of 200 pounds [90.7 kg] at its center ...The real requirement for a table being level is that if it rolls off visibly, no one will want to buy that brand.
The spec Bob quoted are from the BCA rulebook from 50 some years ago. Someone hand retyped (or scanned with text recognition) them at some point 20 some years ago, and missed the +/- on the tolerances. That's what made it to the WPA site and its had that tolerance error since.
One line off on a Starrett 98 series level is .005" per foot. So if you were to slide the level across the table on the short rail on every diamond (which is about 1 foot), it it was off half a line on each diamond, you'd end up at 2 lines total, or .010" for the 50" width of the table. I think most table mechanics try to get within one line about everywhere on the table. That would be above the BCA spec if all the error was pointing in the same direction. If it flips direction back and forth, then it would be better than this BCA spec.
I can tell you that::
a) I have a table on a pier-and-beam floor that moves with moisture content.
So I get to re-level the table multiple times per year.
b) that I shim the table with business cards 0.010" thick
c) you can tell when the table is more than 0.005" out of dead-flat
d) you cannot tell when the table is less than 0.003" out of flat
this is on Simonis 760 with Duramith balls.
a) I have a table on a pier-and-beam floor that moves with moisture content.
So I get to re-level the table multiple times per year.
b) that I shim the table with business cards 0.010" thick
c) you can tell when the table is more than 0.005" out of dead-flat
d) you cannot tell when the table is less than 0.003" out of flat
this is on Simonis 760 with Duramith balls.
DeeDeeCues
Well-known member
Flat has nothing to do with level. I know you are just posting the spec, and I expect the authors thought that flat means level...but it doesn't.
There is a chance that they did know that flat doesn't mean level, in which case their definition and your observable roll-off are a great spec, if the roll-off test is defined.
The test for level being judged by the peers is best.
Any mathematical pursuit for defining level in current terms will be controversial.
Especially at the tournament, is there a ruling for poorly installed tables?
Should they be allowed to have corrections after a player already had a horrible match?
Or should players have to play on the bad table?
Any mathematical pursuit for defining level in current terms will be controversial.
Especially at the tournament, is there a ruling for poorly installed tables?
Should they be allowed to have corrections after a player already had a horrible match?
Or should players have to play on the bad table?
smiling_Hans
Well-known member
If it rolls it is good because at this point the pros are so good they can compensate. They can also play away from any table flaws.
A tournament director that can choose who gets the bad table is a nice perk for officials.
I mean level as I typed it, as compared perpendicular to gravity.
I use Theodolite to get table level.
If there is more than 0.1mm difference on slate level it will show on slow rolls. Most of time tables that i go work for can be 15x more than that error on level of slate.
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If there is more than 0.1mm difference on slate level it will show on slow rolls. Most of time tables that i go work for can be 15x more than that error on level of slate.
DeeDeeCues
Well-known member
I was only commenting on the spec Bob quoted.
Do you just make stuff up to see what it sounds like? Math is objective. Defining something as out of level or not flat can only be done using numbers that you got from measuring. This is the opposite of controversial. What you just said is the same as voting to find out if 2+2=5
My favorite argument in Differential Geometry was arguing that the L2 norm is closer than the Arc Length norm when a piece of flat paper is folded. The demonstration is to fold paper in half and poke a hold. Then separate the fold to have a gap.
The math of the situation is arc length can be shaped differently to change the L2 norm distance.
Flat versus level. Space is curved, what does a flat curve look like? QED.
Is the surface flat from the human perspective or flat on the astronomical scale.
BIRPA support creates research like this.
Movie night is happening.
Maybe we should have stated that:: the surface on the table is perpendicular to the local gravitational vector.
Satisfied ??
DeeDeeCues
Well-known member
I want the one asking the question. I am neither satisfied nor dissatisfied. I only pointed out that they produced a partial specification.
0.1mm per what distance? Per meter?I use Theodolite to get table level.
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If there is more than 0.1mm difference on slate level it will show on slow rolls. Most of time tables that i go work for can be 15x more than that error on level of slate.
This is an hour long video, but it really explains a lot, and how to interpret the readings of the level. It sounds like you are serious about this info, so it's def worth the watch. It's Paul Smith from Diamond. I watched it a couple times over the years. .005" vertical drop per 12" is one division of the Starrett 98 series level, which is what all the USA based mechanics use.
If you want to buy one, check FB marketplace. I bought 3 or 4 of them in the past year for about $60 each. New they are 250-300 range, depending on the seller.
As a spec for manufacturers I think it is OK. There needs to be an additional spec for level for when the table is installed. If the table can't be made flat it can't be made level. And the manufacturer has no control over the installer, usually. I agree that a levelness spec needs to be added.