Here's the latest:
Here's a mobile-friendly online tool (created by "Isaac") and an Excel spreadsheet for automatically calculating the TDF factor from three pocket measurements to determine the difficulty level of a table.
Measurements and data reported by AZB users for table difficulty factor (TDF), based on the table size factor (TSF), pocket size factor (PSF), pocket angle factor (PAF), and pocket shelf factor (PLF):
username - table size:TSF, pocket mouth sizeSF, mouth-throat differenceAF, shelf depthLF - TDF (table description)
Vahmurka - 12':1.25, 7.2cm:1.55, 125deg:0.97, 25mm:0.98 - 1.84 (12ft Russian pyramid table)
Side Pocket - 10':1.10, 4 1/4":1.10, 1 1/4":1.14, 2 1/4":1.07 - 1.48 (10' 1920-1925 Brunswick, modified 9/2016)
Bob Dixon - 9':1.00, 4":1.20, 145deg:1.14, 1 5/8":1.00 - 1.37 (Pool Sharks, Las Vegas, money table, Diamond Pro-Am, red logo, Ernesto Dominguez-modified)
Ricky Sy - 9':1.00, 3 3/4":1.31, 1/4":0.97, 5/8":0.98 - 1.25 (money table at Hard Times in Bellflower, CA)
acedonkeyace - 9":1.00, 4":1.20, 1/2":0.99, 2":1.03 - 1.22 (gamble table at sidePocket in Largo, Florida)
Bonus Ball - 9':1.00, 3 7/8":1.25, 1/8":0.97, 3/4":0.98 - 1.19 (Bonus Ball table)
Marc Vidal - 9':1.00, 4 1/8":1.15, 7/16":1.05, 1":0.98 - 1.18 (shimmed Brunswick Tournament Edition)
chevybob20 - 9':1.00, 4 1/8":1.15, 7/8":1.05, 1":0.98 - 1.18 (Mark-Gregory-modified Centennial)
Qaddiction - 9':1.00, 4 1/8":1.15, 3/4":1.02, 1 3/8":0.99 - 1.16 (Diamond)
ChrisinNC - 10':1.1, 4 3/8":1.05, 11/16":1.02, 1 5/16":0.98 - 1.15 (10' Gabriel Sentinel at Family Billiards in Boone, NC)
rexus31 - 9':1.00, 4":1.20, 3/8":0.98, 1":0.98 - 1.15 (mid to late 50's AMF Commercial Model similar to a Brunswick Anniversary/Sport King)
FatBoy - 9':1.00, 4":1.20, 1/4":0.97, 1":0.98 - 1.14 (Ernesto-Dominguez-modified GC)
TATE - 9':1.00, 4":1.20, 1/4":0.97, 7/8":0.98 - 1.14 (Ernesto-Dominguez-modified GC)
Mikjary - 9'-1.00, 4":1.15, 9/16":1.00, 1 5/16":0.98 - 1.13 (Brunswick Centurion)
Cardigan Kid - 10'-1.10, 4.5":1.00, 0.88":1.04, 1.5":0.98 - 1.12 (Gold Crown from Steinway Billiards - Earl Strickland's former practice/match-up table)
ChrisinNC - 9':1.0, 4 1/8":1.12, 5/8":1.01, 1 1/4":0.98 - 1.12 (tightest Gabriel's Signature Pro at Family Billiards in Boone, NC - Table 7)
Ralph Kramden - 9':1.0, 4 5/16":1.05, 1":1.07, 1 3/4":1.00 - 1.12 (1962 Nine foot Gold Crown 1)
pocket - 9':1.00 - 4 3/16":1.10, 7/16":0.99, 1 7/8":1.03 - 1.12 (unknown)
Neil - 7':0.85, 4 1/8":1.15, 1 1/4":1.14, 1 3/8":0.99 - 1.10 (modified Valley "bar box")
MahnaMahna - 10':1.10, 5 1/2":0.85, 2":1.09, 2 1/2": 1.07 - 1.09 (snooker table poorly converted into a pool table)
Cardigan Kid - 9':1.00, 4 1/4":1.10, 0.45":0.99, 1 5/16":0.99 - 1.08 (GC II)
MSchaffer - 9':1.00, 4 7/16:1.00, 15/16":1.07, 1 5/8":1.00 - 1.07 (GCII, RKC mod)
cigardave - 9':1.00, 4 1/2":1.00, 1":1.07, 1 3/4":1.00 - 1.07 (typical Pro-Cut Diamond)
peppersauce - 9':1.00, 4 1/4":1.10, 3/8":0.98, 1 1/4":0.98 - 1.06 (GC 3)
Side Pocket - 10':1.10, 4 7/8":0.91, 1":1.07, 1 1/2":0.98 - 1.05 (10' 1920-1925 Brunswick)
Pool Hustler - 9':1.00, 4 1/4":1.10, 1/4":0.97, 15/16":0.98 - 1.05 (modified GC, measured by rexus31)
JC, 9':1.00 - 4 7/16":1.00, 143deg:1.07, 1 3/8":0.98 - 1.05 ("Cobrasized" GC III)
SloMoHolic - 9':1.00, 4 1/2":1.00, 7/8":1.04, 1 3/8":0.98 - 1.02 (2005 Diamond Pro with ProCut pockets and Red-label rails)
CoreyClark - 9':1.00, 5":0.91, 1":1.07, 2 1//8":1.05 - 1.02 (GC I)
"standard" table - 9':1.00, 4 7/16":1.00, 9/16":1.00, 1 5/8":1.00 - 1.00 (average-difficulty table)
Goldball - 8':0.90, 12.2cm:0.91, 4cm:1.14, 5.4cm:1.07 - 1.00 (Heiron & Smith)
dr_dave - 9':1.00, 5": 0.91, 1 1/8":1.10, 1 3/8":0.99 - 0.99 (old GC II at MatchUps, Fort Collins)
MVPCues - 9':1.00, 4 1/2":1.00, 1/2":0.98, 1 5/8":1.00 - 0.98 (Antique Brunswick Jefferson, circa 1900)
oldschool1478 - 9':1.00, 4 1/2":1.00, 0.625":1.00, 1.5":0.98 - 0.98 (updated Red Badge Diamond Pro)
freds - 8'+: 0.95, 4.9":0.91, 1.1":1.1, 1.8" 1.03 - 0.98 (Gandy Big G, oversized 8)
Cardigan Kid - 9':1.00, 4 1/2":1.00, 3/4":1.02, 1 1/16":0.95 - 0.97 (GC III Table 7 at Premium Billiards, Syracuse, Mark Gregory-modified w/ Artemis cushions)
wigglybridge - 9':1.00, 4 1/2":1.00, 5/8":1.00, 1 1/2": 0.98 - 0.98 (GC 1.5, rails rebuilt & cushions replaced by Jay Spielberg)
BryanB - 9':1.00, 4 1/2":1.00, 3/4":1.02, 1 1/4":0.95 - 0.97 (1931 Brunswick with double shimmed pockets)
Poolmanis - 9':1.00, 10.9cm:1.05, 1cm:0.97, 3.1cm:0.95 - 0.97 (modified SAM)
Vahmurka - 9':1.0, 12.5cm:0.91, 20mm:1.04, 45mm:1.03 - 0.97 (Brunswick Metro)
mamics - 9':1.00, 4 11/16":0.95, 143deg:1.07, 1 3/16":0.95 - 0.97 (no-name "Chinese Cheapie" with Uylin cushions)
dzcues - 9':1.00, 4 7/8":0.91, 11/16":1.02, 1 15/16":1.03 - 0.96 (typical League-Cut Diamond)
dr_dave - 9':1.00, 5": 0.91, 1":1.07, 1 1/5":0.98 - 0.95 (Olhausen purchased from Robert Byrne)
dzcues - 9':1.00, 5":0.91, 15/16":1.07, 1 1/2":0.98 - 0.95 (Gandy Big G)
Sloppy Pockets - 8'+:0.95, 5":0.91, 1 1/8":1.10, 1 3/4":1.00 - 0.95 (A.E. Schmidt)
44Runner - 8'+/-:0.925, 4 3/8":1.05, 3/4":1.02, 1":0.95 - 0.94 (8' Diamond Pro-Am - blue label)
Corwyn_8 - 9':1.00, 4 3/4":0.95, 1 3/4":1.02, 1 1/4":0.95 - 0.92 (Gandy Winchester)
beetle - 9':1.00, 13.1cm:0.88, 2.2cm:1.03, 4.3cm:1.00 - 0.91 (Olhausen York)
frigopie - 9':1.00, 11.5cm:0.95, 138.7deg:0.98, 3.5cm:0.98 - 0.91 (Eurotour Dynamic III)
12squared - 9':1.00, 4 7/8":0.91, 3/4":1.02, 1 1/2":0.98 - 0.91 (GC home table)
iusedtoberich - 9':1.00, 5 1/8":0.88, 1":1.05, 1 1/2":0.97 - 0.90 (GC)
MSchaffer - 9':1.00, 5 1/8":0.88, 3/4":1.01, 1 3/4":1.00 - 0.89 (GC II)
mfinkelstein3 - 9':1.00, 5 1/8":0.88, 7/8":1.03, 1 1/2": 0.97 - 0.88 (GC III)
StraightPoolIU - 9':1.00, 4 7/8":0.91, 3/4":1.02, 1 1/4":0.95 - 0.88 (GC I)
Vahmurka - 9':1.00, 5 1/8":0.88, 7/8":1.03, 1 1/2": 0.97 - 0.88 (GC)
Dopc - 8':0.90, 4 1/2":1.00, 3/4":1.02, 1 1/4":0.95 - 0.87 (8' Connelly Kayenta)
SloMoHolic - 8':0.90, 4 3/4":0.95, 3/4":1.02, 1 5/8":1.00 - 0.87 (old 8' Brunswick Medalist league table)
RobMan - 9':1.0, 5": 0.88, 3/4":1.01, 1.5":0.97 - 0.86 (GC)
SloMoHolic - 8'+:0.95, 4 7/8":0.91, 7/8":1.04, 1 1/4":0.95 - 0.85 (Brunswick Medalist at Stardust Club in Manchaca, TX)
buckshotshoey - 8':0.90, 4 3/4":0.95, 3/4":1.02, 1 1/2":0.98 - 0.85 (American Heritage "Independence")
nateobot - 7':0.85, 4 3/8":1.05, 1/2":0.95, 1 3/4":1.00 - 0.85 (custom-made)
angluse - 8'+: 0.95, 4 5/8":0.95, 7/16":0.98, 1 3/16:0.95 - 0.84 (1935 Brunswick Challenger)
dr_dave - 8':0.90, 4 3/4":0.95, 5/8":1.00, 1 3/8":0.98 - 0.84 (8' Connelly home table)
BRussell - 8':0.90, 5":0.91, 13/16":1.04, 1 1/2":0.98 - 0.83 (8' Olhausen)
Lovepool - 9':1.00, 13cm:0.88, 1cm:0.96, 3.5cm:0.97 - 0.82 (home table)
jtaylor996 - 7':0.85, 5 1/8":0.88, 146deg:1.09, 1.51":1.00 - 0.82 (7' Legacy home table)
Mooneye - 7':0.85, 4 7/8":0.91, 3/4":1.02, 1 5/8":1.00 - 0.79 (7' Brunswick "Ranchero")
SloMoHolic - 6':0.85, 4 1/2":1.00, 0":0.95, 5/8":0.95 - 0.77 (old 6' Valley "bar box")
dzcues - 7':0.85, 4 1/2":1.00, 0":0.95, 1/2":0.95 - 0.77 (7' Valley "bar box")
dr_dave - 7':0.85, 4 1/2":1.00, 0":0.95, 3/4":0.95 - 0.77 (7' Valley "bar box" at West End, Fort Collins)
_______________________________________
Based on ideas from previous threads on this topic (tight pockets thread and pocket answers thread), and based discussion in the Billiard University (BU) thread concerning how to account for table difficulty in scoring and rating drills like the BU Exams, I decided to create a system for determining how difficult a table plays (based on table and pocket geometry only). It is described in detail in the Table Difficulty Factor (TDF) document, which is convenient if you want a printed copy.
Here's how it works:
The Table Difficulty Factor (TDF) is a percentage measure of how difficult or easy a particular table plays. It is based on table size and the three corner-pocket measurements illustrated below. If the cushion is not 2” (5.1cm) thick, measure the throat size 2” (5.1 cm) back from the cushion noses. You can lay down Post-It Notes or masking tape to better define the lines and intersection points to help with the mouth and throat measurements. If you have an angle-measurement device, you can measure the facing angle directly instead of measuring the throat size. The pocket shelf depth should be measured from the pocket mouth line to the slate top lip edge (where the pocket opening first starts).
Four factors are used to account for table size, pocket size, pocket facing angle, and pocket shelf depth. Each factor is a number less than, equal to, or greater than 1, where 1 indicates average or standard. By multiplying the four factors, you get the TDF which is a good measure of table “toughness.” If TDF=1, the table has an average level of difficulty; if TDF>1, the table plays more difficult than average; and if TDF<1, the table plays easier than average.
The four factors are defined as follows:
The total Table Difficulty Factor (TDF) is then calculated by multiplying the four factors:
The TDF can be used to adjust numbers from any scoring or rating system like the Billiard University Exams, “playing the ghost” drills, the Hopkins Q Skills drill, or the Fargo rating drill. An effective score, taking table difficulty into consideration, can be calculated with:
NOTE – The TDF and effective-score numbers should not be interpreted too literally since there are so many other factors that contribute to how difficult a table actually plays (cloth type and condition, ball conditions, pocket facing and shim properties, rail and cushion conditions, table levelness, humidity, etc.). Here’s a rough scale one can use to put the TDF factor in better perspective:
Here's a mobile-friendly online tool (created by "Isaac") and an Excel spreadsheet for automatically calculating the TDF factor from three pocket measurements to determine the difficulty level of a table.
Measurements and data reported by AZB users for table difficulty factor (TDF), based on the table size factor (TSF), pocket size factor (PSF), pocket angle factor (PAF), and pocket shelf factor (PLF):
username - table size:TSF, pocket mouth sizeSF, mouth-throat differenceAF, shelf depthLF - TDF (table description)
Vahmurka - 12':1.25, 7.2cm:1.55, 125deg:0.97, 25mm:0.98 - 1.84 (12ft Russian pyramid table)
Side Pocket - 10':1.10, 4 1/4":1.10, 1 1/4":1.14, 2 1/4":1.07 - 1.48 (10' 1920-1925 Brunswick, modified 9/2016)
Bob Dixon - 9':1.00, 4":1.20, 145deg:1.14, 1 5/8":1.00 - 1.37 (Pool Sharks, Las Vegas, money table, Diamond Pro-Am, red logo, Ernesto Dominguez-modified)
Ricky Sy - 9':1.00, 3 3/4":1.31, 1/4":0.97, 5/8":0.98 - 1.25 (money table at Hard Times in Bellflower, CA)
acedonkeyace - 9":1.00, 4":1.20, 1/2":0.99, 2":1.03 - 1.22 (gamble table at sidePocket in Largo, Florida)
Bonus Ball - 9':1.00, 3 7/8":1.25, 1/8":0.97, 3/4":0.98 - 1.19 (Bonus Ball table)
Marc Vidal - 9':1.00, 4 1/8":1.15, 7/16":1.05, 1":0.98 - 1.18 (shimmed Brunswick Tournament Edition)
chevybob20 - 9':1.00, 4 1/8":1.15, 7/8":1.05, 1":0.98 - 1.18 (Mark-Gregory-modified Centennial)
Qaddiction - 9':1.00, 4 1/8":1.15, 3/4":1.02, 1 3/8":0.99 - 1.16 (Diamond)
ChrisinNC - 10':1.1, 4 3/8":1.05, 11/16":1.02, 1 5/16":0.98 - 1.15 (10' Gabriel Sentinel at Family Billiards in Boone, NC)
rexus31 - 9':1.00, 4":1.20, 3/8":0.98, 1":0.98 - 1.15 (mid to late 50's AMF Commercial Model similar to a Brunswick Anniversary/Sport King)
FatBoy - 9':1.00, 4":1.20, 1/4":0.97, 1":0.98 - 1.14 (Ernesto-Dominguez-modified GC)
TATE - 9':1.00, 4":1.20, 1/4":0.97, 7/8":0.98 - 1.14 (Ernesto-Dominguez-modified GC)
Mikjary - 9'-1.00, 4":1.15, 9/16":1.00, 1 5/16":0.98 - 1.13 (Brunswick Centurion)
Cardigan Kid - 10'-1.10, 4.5":1.00, 0.88":1.04, 1.5":0.98 - 1.12 (Gold Crown from Steinway Billiards - Earl Strickland's former practice/match-up table)
ChrisinNC - 9':1.0, 4 1/8":1.12, 5/8":1.01, 1 1/4":0.98 - 1.12 (tightest Gabriel's Signature Pro at Family Billiards in Boone, NC - Table 7)
Ralph Kramden - 9':1.0, 4 5/16":1.05, 1":1.07, 1 3/4":1.00 - 1.12 (1962 Nine foot Gold Crown 1)
pocket - 9':1.00 - 4 3/16":1.10, 7/16":0.99, 1 7/8":1.03 - 1.12 (unknown)
Neil - 7':0.85, 4 1/8":1.15, 1 1/4":1.14, 1 3/8":0.99 - 1.10 (modified Valley "bar box")
MahnaMahna - 10':1.10, 5 1/2":0.85, 2":1.09, 2 1/2": 1.07 - 1.09 (snooker table poorly converted into a pool table)
Cardigan Kid - 9':1.00, 4 1/4":1.10, 0.45":0.99, 1 5/16":0.99 - 1.08 (GC II)
MSchaffer - 9':1.00, 4 7/16:1.00, 15/16":1.07, 1 5/8":1.00 - 1.07 (GCII, RKC mod)
cigardave - 9':1.00, 4 1/2":1.00, 1":1.07, 1 3/4":1.00 - 1.07 (typical Pro-Cut Diamond)
peppersauce - 9':1.00, 4 1/4":1.10, 3/8":0.98, 1 1/4":0.98 - 1.06 (GC 3)
Side Pocket - 10':1.10, 4 7/8":0.91, 1":1.07, 1 1/2":0.98 - 1.05 (10' 1920-1925 Brunswick)
Pool Hustler - 9':1.00, 4 1/4":1.10, 1/4":0.97, 15/16":0.98 - 1.05 (modified GC, measured by rexus31)
JC, 9':1.00 - 4 7/16":1.00, 143deg:1.07, 1 3/8":0.98 - 1.05 ("Cobrasized" GC III)
SloMoHolic - 9':1.00, 4 1/2":1.00, 7/8":1.04, 1 3/8":0.98 - 1.02 (2005 Diamond Pro with ProCut pockets and Red-label rails)
CoreyClark - 9':1.00, 5":0.91, 1":1.07, 2 1//8":1.05 - 1.02 (GC I)
"standard" table - 9':1.00, 4 7/16":1.00, 9/16":1.00, 1 5/8":1.00 - 1.00 (average-difficulty table)
Goldball - 8':0.90, 12.2cm:0.91, 4cm:1.14, 5.4cm:1.07 - 1.00 (Heiron & Smith)
dr_dave - 9':1.00, 5": 0.91, 1 1/8":1.10, 1 3/8":0.99 - 0.99 (old GC II at MatchUps, Fort Collins)
MVPCues - 9':1.00, 4 1/2":1.00, 1/2":0.98, 1 5/8":1.00 - 0.98 (Antique Brunswick Jefferson, circa 1900)
oldschool1478 - 9':1.00, 4 1/2":1.00, 0.625":1.00, 1.5":0.98 - 0.98 (updated Red Badge Diamond Pro)
freds - 8'+: 0.95, 4.9":0.91, 1.1":1.1, 1.8" 1.03 - 0.98 (Gandy Big G, oversized 8)
Cardigan Kid - 9':1.00, 4 1/2":1.00, 3/4":1.02, 1 1/16":0.95 - 0.97 (GC III Table 7 at Premium Billiards, Syracuse, Mark Gregory-modified w/ Artemis cushions)
wigglybridge - 9':1.00, 4 1/2":1.00, 5/8":1.00, 1 1/2": 0.98 - 0.98 (GC 1.5, rails rebuilt & cushions replaced by Jay Spielberg)
BryanB - 9':1.00, 4 1/2":1.00, 3/4":1.02, 1 1/4":0.95 - 0.97 (1931 Brunswick with double shimmed pockets)
Poolmanis - 9':1.00, 10.9cm:1.05, 1cm:0.97, 3.1cm:0.95 - 0.97 (modified SAM)
Vahmurka - 9':1.0, 12.5cm:0.91, 20mm:1.04, 45mm:1.03 - 0.97 (Brunswick Metro)
mamics - 9':1.00, 4 11/16":0.95, 143deg:1.07, 1 3/16":0.95 - 0.97 (no-name "Chinese Cheapie" with Uylin cushions)
dzcues - 9':1.00, 4 7/8":0.91, 11/16":1.02, 1 15/16":1.03 - 0.96 (typical League-Cut Diamond)
dr_dave - 9':1.00, 5": 0.91, 1":1.07, 1 1/5":0.98 - 0.95 (Olhausen purchased from Robert Byrne)
dzcues - 9':1.00, 5":0.91, 15/16":1.07, 1 1/2":0.98 - 0.95 (Gandy Big G)
Sloppy Pockets - 8'+:0.95, 5":0.91, 1 1/8":1.10, 1 3/4":1.00 - 0.95 (A.E. Schmidt)
44Runner - 8'+/-:0.925, 4 3/8":1.05, 3/4":1.02, 1":0.95 - 0.94 (8' Diamond Pro-Am - blue label)
Corwyn_8 - 9':1.00, 4 3/4":0.95, 1 3/4":1.02, 1 1/4":0.95 - 0.92 (Gandy Winchester)
beetle - 9':1.00, 13.1cm:0.88, 2.2cm:1.03, 4.3cm:1.00 - 0.91 (Olhausen York)
frigopie - 9':1.00, 11.5cm:0.95, 138.7deg:0.98, 3.5cm:0.98 - 0.91 (Eurotour Dynamic III)
12squared - 9':1.00, 4 7/8":0.91, 3/4":1.02, 1 1/2":0.98 - 0.91 (GC home table)
iusedtoberich - 9':1.00, 5 1/8":0.88, 1":1.05, 1 1/2":0.97 - 0.90 (GC)
MSchaffer - 9':1.00, 5 1/8":0.88, 3/4":1.01, 1 3/4":1.00 - 0.89 (GC II)
mfinkelstein3 - 9':1.00, 5 1/8":0.88, 7/8":1.03, 1 1/2": 0.97 - 0.88 (GC III)
StraightPoolIU - 9':1.00, 4 7/8":0.91, 3/4":1.02, 1 1/4":0.95 - 0.88 (GC I)
Vahmurka - 9':1.00, 5 1/8":0.88, 7/8":1.03, 1 1/2": 0.97 - 0.88 (GC)
Dopc - 8':0.90, 4 1/2":1.00, 3/4":1.02, 1 1/4":0.95 - 0.87 (8' Connelly Kayenta)
SloMoHolic - 8':0.90, 4 3/4":0.95, 3/4":1.02, 1 5/8":1.00 - 0.87 (old 8' Brunswick Medalist league table)
RobMan - 9':1.0, 5": 0.88, 3/4":1.01, 1.5":0.97 - 0.86 (GC)
SloMoHolic - 8'+:0.95, 4 7/8":0.91, 7/8":1.04, 1 1/4":0.95 - 0.85 (Brunswick Medalist at Stardust Club in Manchaca, TX)
buckshotshoey - 8':0.90, 4 3/4":0.95, 3/4":1.02, 1 1/2":0.98 - 0.85 (American Heritage "Independence")
nateobot - 7':0.85, 4 3/8":1.05, 1/2":0.95, 1 3/4":1.00 - 0.85 (custom-made)
angluse - 8'+: 0.95, 4 5/8":0.95, 7/16":0.98, 1 3/16:0.95 - 0.84 (1935 Brunswick Challenger)
dr_dave - 8':0.90, 4 3/4":0.95, 5/8":1.00, 1 3/8":0.98 - 0.84 (8' Connelly home table)
BRussell - 8':0.90, 5":0.91, 13/16":1.04, 1 1/2":0.98 - 0.83 (8' Olhausen)
Lovepool - 9':1.00, 13cm:0.88, 1cm:0.96, 3.5cm:0.97 - 0.82 (home table)
jtaylor996 - 7':0.85, 5 1/8":0.88, 146deg:1.09, 1.51":1.00 - 0.82 (7' Legacy home table)
Mooneye - 7':0.85, 4 7/8":0.91, 3/4":1.02, 1 5/8":1.00 - 0.79 (7' Brunswick "Ranchero")
SloMoHolic - 6':0.85, 4 1/2":1.00, 0":0.95, 5/8":0.95 - 0.77 (old 6' Valley "bar box")
dzcues - 7':0.85, 4 1/2":1.00, 0":0.95, 1/2":0.95 - 0.77 (7' Valley "bar box")
dr_dave - 7':0.85, 4 1/2":1.00, 0":0.95, 3/4":0.95 - 0.77 (7' Valley "bar box" at West End, Fort Collins)
_______________________________________
Based on ideas from previous threads on this topic (tight pockets thread and pocket answers thread), and based discussion in the Billiard University (BU) thread concerning how to account for table difficulty in scoring and rating drills like the BU Exams, I decided to create a system for determining how difficult a table plays (based on table and pocket geometry only). It is described in detail in the Table Difficulty Factor (TDF) document, which is convenient if you want a printed copy.
Here's how it works:
The Table Difficulty Factor (TDF) is a percentage measure of how difficult or easy a particular table plays. It is based on table size and the three corner-pocket measurements illustrated below. If the cushion is not 2” (5.1cm) thick, measure the throat size 2” (5.1 cm) back from the cushion noses. You can lay down Post-It Notes or masking tape to better define the lines and intersection points to help with the mouth and throat measurements. If you have an angle-measurement device, you can measure the facing angle directly instead of measuring the throat size. The pocket shelf depth should be measured from the pocket mouth line to the slate top lip edge (where the pocket opening first starts).
Four factors are used to account for table size, pocket size, pocket facing angle, and pocket shelf depth. Each factor is a number less than, equal to, or greater than 1, where 1 indicates average or standard. By multiplying the four factors, you get the TDF which is a good measure of table “toughness.” If TDF=1, the table has an average level of difficulty; if TDF>1, the table plays more difficult than average; and if TDF<1, the table plays easier than average.
The four factors are defined as follows:
The total Table Difficulty Factor (TDF) is then calculated by multiplying the four factors:
TDF = TSF x PSF x PAF x PLF
The TDF can be used to adjust numbers from any scoring or rating system like the Billiard University Exams, “playing the ghost” drills, the Hopkins Q Skills drill, or the Fargo rating drill. An effective score, taking table difficulty into consideration, can be calculated with:
(effective score) = (raw score) x TDF
NOTE – The TDF and effective-score numbers should not be interpreted too literally since there are so many other factors that contribute to how difficult a table actually plays (cloth type and condition, ball conditions, pocket facing and shim properties, rail and cushion conditions, table levelness, humidity, etc.). Here’s a rough scale one can use to put the TDF factor in better perspective: