The thread on the outer hexagon screw is generally fine tooth common thread, and the ring tooth common thread outer hexagon screw has good self-selling property, which is mainly used on thin-walled parts or under impact, vibration or alternating load.

Generally speaking, the outer hexagonal screws are made into partial threads, and the full-threaded outer hexagonal screws are mainly used in occasions where the nominal length of the outer hexagonal screw is short and the longer thread is required. External hexagon screws with holes are used in situations where external hexagon screws are required to be locked. The outer hexagonal screw with hinged hole can accurately fix the phase position of the connected part. And can be sheared and extruded by the mold force.

The advantage of the outer hexagon is that the pretightening contact area is large, and a large pretightening force can be used, which is generally used in large equipment, the price is lower than the inner hexagon, but the disadvantage is that it occupies a large space and can not be used in countersunk holes.

The inner hexagonal screw is often used in machinery, which mainly has the advantages of easy fastening, disassembly, not easy to slip angle and so on. The inner hexagon wrench is usually a 90 °turn. One end is long and the other is short. When using the short side to hit the screw, the long side of the hand can save a lot of force and tighten the screw better. The long end has a split head (hexagonal cylinder similar to a sphere) and a flat head, which can be easily inclined to disassemble and install some inconvenient parts of the wrench.

The manufacturing cost of the outer hexagon is much lower than that of the inner hexagon, and its advantage is that the screw (the force position of the wrench) is thinner than the inner hexagon, and in some places it can not be replaced by the inner hexagon. In addition, the machines with low cost, low dynamic strength and low precision use much less inner hexagon screws than outer hexagons.

The advantage of the inner hexagon is that it takes up a small space and can be used as a countersunk head, which is generally used in small equipment, but the disadvantage is that the pretightening contact area is small and can not use too much pretightening force, and the price is a little more expensive. If it exceeds a certain length, there will be no full thread.