The table of contents
- Determining the wrench number by the diameter of the fastener thread
- Selecting Inch Wrenches
- Wrench sizes for hexagonal socket screws
Wrench size 24
Determining the wrench number by the thread diameter of the fastener
The key size of a hexagonal bolt or nut is the distance between two parallel lying faces. You can quickly and accurately find it out, without resorting to a ruler or caliper, by the diameter of the threaded part, which is listed in the technical information for the fastener. The fact is that each standard thread diameter corresponds to a certain size of the working profile of the fastener - basic (normal), reduced and increased. Bolts with reduced and increased size of the head are much rarer.
According to the table, you can easily determine what size wrench is suitable for a particular bolt from M1 to M110.
Table 1. Wrench sizes for metric bolts and nuts.
Thread diameter, М | Turn key size | ||
main S, мм | reduced S, мм | enlarged S, мм | |
М1 | 3.2 | - | - |
М1.2 | 3.2 | - | - |
М1.4 | 3.2 | - | - |
М1.6 | 3.2 | - | - |
М2 | 4 | - | - |
М2.5 | 5 | - | - |
М3 | 5.5 | - | - |
М4 | 7 | - | - |
М5 | 8 | - | - |
М6 | 10 | - | - |
М7 | 11 | - | - |
М8 | 13 | 12 | - |
М10 | 17 (16) | 14 | - |
М12 | 19 (18) | 17 | 21 (22) |
М14 | 22 (21) | 19 | 24 |
М16 | 24 | 22 | 27 |
М18 | 27 | 24 | 30 |
М20 | 30 | 27 | 32 (34) |
М22 | 32 (34) | 30 | 36 |
М24 | 36 | 32 | 41 |
М27 | 41 | 36 | 46 |
М30 | 46 | 41 | 50 |
М33 | 50 | - | 55 |
М36 | 55 | 50 | 60 |
М39 | 60 | 55 | 65 |
М42 | 65 | 60 | 70 |
М48 | 75 | - | 75 |
М52 | 80 | - | 80 |
М56 | 85 | - | - |
М60 | 90 | - | - |
М64 | 95 | - | - |
М68 | 100 | - | - |
М72 | 105 | - | - |
М76 | 110 | - | - |
М80 | 115 | - | - |
М85 | 120 | - | - |
М90 | 130 | - | - |
М95 | 135 | - | - |
М100 | 145 | - | - |
М105 | 150 | - | - |
М110 | 155 | - | - |
The sizes of the hexagon socket are defined in the standard GOST 6424-73. When properly selected, the gap between the jaws of the tool and the faces of the fastener does not exceed 0.1 - 0.3 mm.
Selecting Inch Wrenches
The size of the inch wrench is expressed in inches and refers not to the width of the wrench's shed, but to the diameter of the threads of the inch fasteners it is designed to work with. The hexagonal working profile of inch bolts and nuts differs in size from the metric standard by a fraction of a millimeter. Therefore, metric wrenches will either not fit on the faces of inch fasteners, or they won't fit at all. You need inch wrenches and sockets to work with it.
Table 2. UNC/UNF threads and key nut size.
Thread diameter (wrench size), inch | Wrench nut size, inch | Wrench nut size, mm |
1/4 | 7/16 | 11.11 |
5/16 | 1/2 | 12.7 |
3/8 | 9/16 | 14.29 |
7/16 | 5/8 | 15.88 |
1/2 | 3/4 | 19.05 |
9/16 | 13/16 | 20.63 |
5/8 | 15/16 | 23.81 |
3/4 | 1 1/8 | 28.58 |
7/8 | 1 5/16 | 33.34 |
1 | 1 1/2 | 38.10 |
1 1/8 | 1 11/16 | 42.86 |
1 1/4 | 1 7/8 | 47.63 |
1 3/8 | 2 1/16 | 52.39 |
1 1/2 | 2 1/4 | 53.15 |
1 3/4 | 2 5/8 | 66.68 |
2 | 3 | 76.20 |
2 1/4 | 3 3/8 | 85.73 |
2 1/2 | 3 3/4 | 95.25 |
2 3/4 | 4 1/8 | 104.76 |
3 | 4 1/2 | 114.30 |
Wrench sizes for bolts with internal hexagon
In the mechanical engineering and instrumentation along with hexagonal fasteners are widely used bolts with cylindrical head, for screwing which the hexagonal angle wrench is used. They are made according to DIN 912 or GOST 11738-84, according to which each thread diameter must correspond to a certain size "under the key" (the distance between the opposite faces of the internal hexagon).
Crescent wrench with ball for Allen screws
Compliance Table:
Thread, M | М4 | М5 | М6 | М8 | М10 | М12 | М14 | М16 | М18 | М20 | М22 | М24 | М27 | М30 | М33 | М36 |
Turnkey size, mm | 3 | 4 | 5 | 6 | 8 | 10 | 12 | 14 | 14 | 17 | 17 | 19 | 19 | 22 | 24 | 27 |
Before you start disassembling a car, servicing a bicycle or repairing garden equipment, it's a good idea to make sure you have all the tools you need. It is a good idea to have a table of key sizes for bolts and nuts handy. When repairing old machinery often faces the problem of unscrewing damaged parts. In order to work with fasteners with worn-out sides you can purchase special twist heads AN0400120 at the "Krepkom" store and for removing screws with ripped-off heads we offer a set of thread extractors AG010048.