What diameter is a 2 56 screw

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Thread designations for inch threads

UNC thread: Unified Coarse Thread Series, American standard coarse thread

Example: 3/8 "- 16 x 1/2" hex bolt
3/8 = outer thread diameter 9.53 mm
16 = number of threads on 1 inch (25.40 mm) length
1/2 = length of the screw from the head 12.70 mm

UNF thread:

Unified National Fine Thread Series, American standard fine thread
Example: 3/8 "- 24 x 1/2" hex bolt
3/8 = outer thread diameter 9.53 mm
24 = number of threads on 1 inch (25.40 mm) length
1/2 = length of the screw from the head

Thread for the photo area
Camera thread, tripod thread, or also referred to as large and small photo thread
1/4 inch UNC thread
6.35 mm outer thread diameter, American coarse thread UNC
3/8 inch UNC thread
9.53 mm outer thread diameter, American coarse thread UNC

Wrench sizes and thread diameters for hexagon
Inch screws and nuts

Thread diameter Thread diameter Wrench size Wrench size
in inches in millimeters screw nut

1/4                                   6,350                             7/16                    7/16
5/16                                 7,935                             1/2                      1/2
3/8                                  9,525                              9/16                     9/16
7/16                               11,113                             5/8                     11/16
1/2                                12,700                              3/4                       3/4
9/16                              14,288                             13/16                    7/8
5/8                                15,875                             15/16                  15/16
3/4                                19,050                             1 1/8                   1 1/8
7/8                                22,225                             1 5/16                 1 5/16
1                                   25,400                             1 1/2                   1 1/2

 

UNC thread No. 1 - 12 

Thread identification Thread diameter Diameter of turns each
in millimeters core hole in mm inches

1 - 64 UNC 1.854 1.50 64
2 - 56 UNC 2.184 1.78 56
3 - 48 UNC 2.515 2.05 48
4 - 40 UNC 2.845 2.27 40
5 - 40 UNC 3.175 2.59 40
6 - 32 UNC 3.505 2.77 32
8-32 UNC 4.166 3.42 32
10-24 UNC 4.826 3.82 24
12-24 UNC 5.486 4.47 24

 

UNF thread No. 0 - 12

Thread identification Thread diameter Diameter of turns each
in millimeters core hole in mm inches

0 - 80 UNF 1.524 1.25 80
1 - 72 UNF 1.854 1.55 72
2 - 64 UNF 2.184 1.90 64
3 - 56 UNF 2.515 2.15 56
4 - 48 UNF 2.845 2.40 48
5 - 44 UNF 3.175 2.70 44
6 - 40 UNF 3.505 2.95 40
8 - 36 UNF 4.166 3.50 36
10 - 32 UNF 4.826 4.10 32
12 - 28 UNF 5.486 4.70 28