Compared With The Outer Hexagon Screws And The Inner Hexagon Screws, Why Do Mechanical Equipment Always Prefer The Inner Hexagon?
Mar 16, 2023
Today's mechanical equipment needs fasteners if they want to be able to operate normally, but I found many design drawings and found that almost all designs use hexagon socket screws, regardless of whether the countersunk hole is or not.
I am very puzzled, why do many devices use inner hexagonal screws instead of outer hexagonal screws? What is so good about it?
Hexagonal screws are hexagonal bolts
The threads on the outer hexagonal screws are generally ordinary threads with fine teeth, and the outer hexagonal screws with ordinary threaded threads have better self-saleability. They are mainly used on thin-walled parts or where they are subject to shock, vibration or alternating loads.
Generally, the outer hexagon screws are partially threaded, and the full-thread outer hexagon screws are mainly used for outer hexagon diameters with a shorter nominal length and where longer threads are required. Hexagon socket head screws with holes are used in occasions where hexagon socket head screw locking is required. The external hexagonal screws with reamed holes can accurately fix the relative position of the connected parts. And can be sheared and squeezed by the mold force.
The advantage of the outer hexagon is that it has a large preload contact area and can use a large preload force. It is generally used on large equipment, and the price is lower than that of the inner hexagon. The disadvantage is that it takes up a lot of space and cannot be used in the counterbore.
Hexagon socket screws are often used in machinery, mainly because they are easy to fasten, disassemble, and not easy to slip. Allen wrenches generally have a 90° turn. One end is long and the other is short. When screwing with the short side, holding the long side can save a lot of force and tighten the screw better. The long end has a round head (a hexagonal cylinder similar to a sphere) and a flat head. The round head can be easily obliquely inserted and disassembled, and it can be installed in some parts where it is inconvenient to use a wrench.
The manufacturing cost of the outer hexagon is much lower than that of the inner hexagon, and its advantage is that the screw head (where the wrench is stressed) is thinner than the inner hexagon, and some places cannot be replaced by the inner hexagon. In addition, machines with low cost, low power strength, and low precision requirements use much fewer inner hexagonal screws than outer hexagonal screws.
The advantage of the inner hexagon is that it takes up less space and can be used as a countersunk head. It is generally used on small equipment. The disadvantage is that the pre-tightening contact area is small and the pre-tightening force cannot be used too much.
Then why can hexagon socket screws appear on many mechanical equipment?
1. Greater load bearing
There are six stress-bearing surfaces of hexagon socket head bolts, which are more resistant to screwing than flat-head screws and cross-shaped screws with only two sides.
Advantages and disadvantages of outer hexagon screws and inner hexagon screws. But why do you always prefer the inner hexagon?
Note: The material of hexagon socket bolts is generally made of stainless steel, carbon steel, and alloy steel. There is basically no difference in material from other types of screws. The higher the performance level, the greater the strength. When selecting screws, you must choose strictly according to the use requirements. Screws with suitable performance grades have different grades and different prices.
2. Can be buried in processing
The whole nut sinks into the workpiece, which can keep the surface of the workpiece smooth and beautiful.
3. Easy to install
Compared with the outer hexagonal screw, the inner hexagon is suitable for more assembly occasions, especially narrow occasions, so it is very convenient for assembly and maintenance, and it is also convenient for debugging.
Four, not easy to disassemble
The tools we usually use are adjustable wrenches, screwdrivers and dull wrenches, etc., but special wrenches must be used to disassemble the hexagon socket head bolts. Therefore, it is not easy for ordinary people to disassemble, which is also a benefit.
