A nut is a type of fastener with a threaded hole. Nuts are almost always used in conjunction with a mating bolt to fasten two or more parts together. The two partners are kept together by a combination of their threads' friction, a slight stretching of the bolt, and compression of the parts to be held together.
GRADE | CHEMICAL COMPOSITION1(%MAXIMA UNLESS STATED) | NOTES | ALTERNATIVE NAMES | ||||||||
C | Si | Mn | P | S | Cr | Mo | Ni | Cu | |||
A1 | 0.12 | 1 | 6.5 | 0.2 | 0.15/0.35 | 16-19 | 0.7 | 5-10 | 1.75-2.25 | 2 3 4 | 303S31,303S42,1.4305 |
A2 | 0.1 | 1 | 2 | 0.05 | 0.03 | 15-20 | 5 | 8-19 | 4 | 6 7 | 304,394S17(BS3111),1.4301,1.4567 |
A3 | 0.08 | 1 | 2 | 0.045 | 0.03 | 17-19 | 5 | 9-12 | 1 | 8 | 321,1.4541,347,1.4550 |
A4 | 0.08 | 1 | 2 | 0.045 | 0.03 | 16-18.5 | 2-3 | 10-15 | 4 | 7 9 | 316,1.4401,1.4578 |
A5 | 0.08 | 1 | 2 | 0.045 | 0.03 | 16-18.5 | 2-3 | 10.5-14 | 1 | 8 9 | 316Ti,1.4571,316Cb,1.4580 |
C1 | 0.09-0.15 | 1 | 1 | 0.05 | 0.03 | 11.5-14 | - | 1 | - | 9 | 410,1.4006 |
C3 | 0.17-0.25 | 1 | 1 | 0.04 | 0.03 | 16-18 | - | 1.5-2.5 | - |
|
431,1.4057 |
C4 | 0.08-0.15 | 1 | 1.5 | 0.06 | 0.15-0.35 | 12-14 | 0.8 | 1 |
|
2 9 | 416,1.4005 |
F1 | 0.12 | 1 | 1 | 0.04 | 0.03 | 15-18 | 10 | 1 |
|
11 12 | 430,1.4016,430Ti,1.4520,430Cb,1.4511 |
In applications where vibration or rotation may work a nut loose, various locking mechanisms may be employed: lock washers, jam nuts, specialist adhesive thread-locking fluid such as Loctite, safety pins (split pins) or lockwire in conjunction with castellated nuts, nylon inserts (Nyloc nut), or slightly oval-shaped threads.
The most common shape is hexagonal, for similar reasons as the bolt head - 6 sides give a good granularity of angles for a tool to approach from (good in tight spots), but more (and smaller) corners would be vulnerable to being rounded off. It takes only 1/6th of a rotation to obtain the next side of the hexagon and grip is optimal. However polygons with more than 6 sides do not give the requisite grip and polygons with fewer than 6 sides take more time to be given a complete rotation. Other specialized shapes exist for certain needs, such as wingnuts for finger adjustment and captive nuts (e.g.