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Ko-ken Part Numbering System

Learning the Ko-ken Part Numbering System

1) The first digit denotes the Square Drive.
  2 = 1/4"
3 = 3/8"
4 = 1/2"
6 = 3/4"
8 = 1"
7 = 1 1/2"
 

All Square Drive codes that are prefixed with a 1 refer to an Impact Socket/Accessory/Set, etc. for example:

 CODE    
(1)2 1 = Impact 2 = 1/4" Drive...
(1)3 1 = Impact 3 = 3/8" Drive...
(1)4 1 = Impact 4 = 1/2" Drive...
(1)6 1 = Impact 6 = 3/4" Drive...
(1)8 1 = Impact 8 = 1" Drive...
(1)7 1 = Impact 7 = 1 1/2: Drive...
2)

The second digit denotes the type of tool. For example:

0 = Bit Sockets 20... = 1/4" Drive Bit Socket
2 = Sets 22... = 1/4" Drive Set
3 = Deep Sockets 23... = 1/4" Drive Deep Socket
4 = Standard Sockets 24... = 3/8" Drive Std Socket
7 = Accessories 37... = 3/8" Drive Accessory
3)

The third and fourth digits refer to the type of Socket or Accessory:

00 = 6 Point Socket 49/50/52/53 = Ratchet
05 = 12 Point Socket 60 = Extension Bar
10/11/12/20/25 = Special Type Sockets 68 = Hinge Bar
15 = 8 Point Socket 70/71 = Universal Joint Style
  85 = Sliding "T" Handle
 

These numbers repeat themselves throughout the range for the same tools in various Square Drives, for example:

 CODE      
6405 6 = 3/4" Drive 4 = Std Socket 05 = 12 Point
4400 4 = 1/2" Drive 4 = Std Socket 00 = 6 Point
2300 2 = 1/4" Drive 3 = Deep Socket 00 = 6 Point
8770 8 = 1" Drive 7 = Accessory 70 = Universal
4)

Codes that end with A = Imperial, M = Metric and W = Whitworth identify the type of socket, for

CODE        
3400A 3 = 3/8" Drive 4 = Std Socket 00 = 6 Point A = Imperial
4400M 4 = 1/2" Drive 4 = Std Socket 00 = 6 Point M = Metric
3405W 3 = 3/8" Drive 4 = Std Socket 05 = 12 Point W = Whitworth