socket wrenches
metric sizes

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The tables below show the commonly-available sizes of socket wrench and the fasteners they fit. A 12-pt socket fits both hexagonal, square, and 12-pt heads (the last found only in aerospace bolts).

Sockets are made that are deeper than the normal socket, so that they will fit over bolts that protrude so far that a normal socket will not come down far enough to engage the nut. In the column headings, these are indicated by a “d”.

One end of a socket has a square recess which fits the socket wrench. In consumer wrenches, the square drives are ¼″, 3/8″, ½″, and ¾″.

American Socket Wrenches: Metric Sizes to 36mm
Size
(mm)
¼″ drive 3/8″ drive ½″ drive Fits bolt or nut with this diameter
6
pt
12
pt
6pt
d
6
pt
12
pt
6pt
d
12pt
d
6
pt
12
pt
6pt
d
12
d
ANSI
cap screws,
formed hex screws,
standard metric
ANSI
heavy hex
ISO J.I.S.
(Japan)
D.I.N
(Germany)
3                                
4 .                     M2×0.4        
5 .                     M2.5×0.45        
5.5                       M3×0.5   3   3
6 .                     M3.5×0.6     3  
7 .                     M4×0.7   4   4
8 .                     M5×0.8     4 5
9 .     . . . . . .           5  
10 .     . . . . . .     M6×1     6 6
11 .     . . . . . .         7 7 7
12 . . . . . . . . .         8    
13 . . . . . . . . .     M8×1.25       8
14   .   . . . . . .   .     10 8  
15       . . . . . .     M10×1.5*        
16         . . .   .     M10×1.5        
17       . . . . . .   .     12 10 10
18         . . .   .     M12×1.75        
19       . . . . . .   .     14 12 12
20                                
21                 .   . M14×2 M12×1.75   14  
22               . .   .     16   14
23                             16  
24                 .     M16×2 M14×2     16
27                 .   .   M16×2      
30                 .     M20×2.5        
32                 .              
34                         M20×2.5      
36                 .     M24×3        

* Produced in the US, but not an ISO size. The 16mm between flats should be used instead.

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