Advantages and disadvantages of common nuts

In some important cases, some anti-loose measures will be taken to ensure the reliability of the nut locking. The use of lock nut is one of the anti-loose measures. The working principle of the nut is self-locking by the friction between the nut and the bolt. However, the reliability of this self-locking in dynamic loads is reduced.

There are three types of lock nuts:

The first type is to drill a threaded hole (usually 2~3, evenly distributed on the outer round surface) on the outer surface of the nut to the inner circular thread surface, which is used to screw a small diameter countersunk head screw. Apply a centripetal force to the threads to prevent the lock nut from loosening. A disadvantage of such a lock nut is that it is difficult to disassemble and reload.

The second is to use two identical nuts to screw on the same bolt, and a tightening torque is added between the two nuts to make the bolt connection reliable.

The third is a special locknut that needs to be used with a lockable gasket. The special locknut is not a hex nut, but a round nut. The ball screw has 3~8 notches on the circumference of the nut (depending on the size of the nut and the manufacturer's product range). These gaps are Tighten the point of the tool and the snap-in of the lock tab.

Screws and nuts common using mistakes

1.The holes of screws and nuts are not suitable

On the machine bears the transverse load and the shear force action screw nut (such as the transmission shaft bolt, flywheel bolt), they and the bolt hole fit for the transition fit, assembly should be strong and reliable, and can withstand the lateral force.Some people do not pay attention to check in the assembly, bolt and bolt hole between the larger gap is still installed, the result of bolt loose or cut off accident.

2.screw nut to thick instead of fine

The machine on the important joint parts, such as the transmission shaft, fly shaft, etc., its bolt multi-purpose fine thread.When parts are missing in maintenance, coarse - tooth bolts are used instead.Due to the large internal diameter of fine tooth bolts, smaller pitch and outer Angle, high strength, good self-locking performance and other advantages, strong ability to withstand impact, vibration and exchange load;After replacing with coarse bolt, it is easy to loosen, take off and break, causing mechanical accidents.

3.screw nut a mother pad

In the installation, sometimes there will be assembly after the screw nut is too long phenomenon, so some people will be installed in a bolt on a lot of spring washer, so, in the process of strengthening the spring washer force is uneven, some will break, so that the bolt pre-tightening force down;Or produce eccentric load, reduce the reliability of bolt connection.

4.The washer of screw and nut is too large

Sometimes due to the lack of suitable washers, someone will use a larger diameter of the washer instead.In this way, the contact area between the bolt head and the washer is small, and the bearing pressure or locking force of the washer drops. Under the action of vibration and impact load, the bolt is easy to loosen.

5.Thicken nuts

Some people often mistakenly believe that thickening nuts can increase the number of working cycles of the thread, thus improving the reliability of the connecting parts, in fact, the thicker the nut, the more uneven load distribution between the threads, the more likely to lead to loose connecting parts.

6.The torque of the screw and nut is inconsistent

Many people think that the screw and nut should be "tight rather than loose", so they consciously increase the tightening torque of the screw and nut, resulting in screw and nut sliding buckle.

7.false strong snails

Bolt, nut or screw hole thread with rust stains, scale, iron filings, sand and other impurities, or join a joint surface impurities such as burrs, sediment, and not be removed before assembly, when tightening bolts, due to the effect of blocking of the impurity, on the surface of screw tightly, torque value meet the requirements, but actually has not really compact connection;In addition, there is a situation, due to the screw hole mud, scale and other impurities jacking role, although the bolt torque is in line with the provisions, but the working parts are not compressed.Under this false solidity, vibration, load shock, and temperature variations often cause bolts to loosen quickly.

8.Improper locking of screws and nuts

After screw and nut assembly, anti-loose device should be adopted for locking.When using cotter pin lock, the common mistake is to use too fine open lock or half open lock lock;The use of spring gasket locking, the common mistake is that the gasket opening error distance is too small, loss of elasticity;If the locking plate is used, the common mistake is to lock the locking plate at the corner of the nut.For double-nut locking, a common mistake is to put the thinner nut on the outside and not screw it tight enough.

About the screws head shapes and screws drives

A screw has two distinct characteristics：head shapes and screw drives.

Screws head shapes:

The shape of your screw head may not seem important, but each head type is made that way for a reason, usually enabling you to create your project easier, and with your preferred finish.

The head of a screw is where your screw will stop. Only the threaded part will be beneath the surface of your project, leaving the head outside, or flush with, the surface.

Some head shapes assist to create the look of the finished product, but they also usually have a purpose beyond aesthetics. The head shape of the screw also helps you drive the screw into your material using your force and the mechanics of the screws.

Screws drives:

The slotted screw drive simply has a single slot in the head of the fastener and is driven by a flat-bladed screwdriver. The slotted screw drive was the first to be developed and was for centuries the most common, simplest and cheapest drive to make. It works well when hand driven, but is not often used with power tools as the screw driver can easily slip out of the slot and damage the surrounding material.

The One Way Drive screw is a “tamper free” design. It is sometimes referred to as the one-way clutch. These screws are driven in with a standard flat-blade screwdriver but cannot be easily unscrewed because of the design. A special tool called a “one way tool extractor” can be used to unscrew it. Also various methods such as drilling, cutting, using locking pliers, and inserting a drill chuck into the head of the screw much in the fashion of removing screws with broken heads can be used.

The Hex Drive is a six point fastener head. It is often known as a hex head cap screw or a hex head machine screw. This head style can be driven with a wrench or with 6 or 12 point sockets.

The Hex Socket Drive has a rounded head with a hexagonal recess and is driven by a hex wrench often referred to as an Allen Wrench. There are tamper resistant versions with a pin in the recess.

Torx™ is the trademark for a type of screw head characterized by a 6-point-star-shape. It was developed in 1967. The official name given it by the International Organization for Standardization is “hexalobular internal driving feature”. The Torx™ is designed to allow for higher torque to be exerted on a screw when compared to a similarly sized hex socket head. Unlike Phillips drives, Torx™ heads were designed to prevent cam-out, allowing them to over torque the screw. Torx™ is commonly used in automobiles, computer systems, and consumer electronics. There is a tamper resistant Torx™ drive, which has a small pin inside the recess.

The Phillips design was created by John Thompson. When he was unable to convince manufacturers to use his products he sold the design to Henry F. Phillips. Phillips is credited with forming Phillips Screw Company which promoted and improved the design. The original patent ran out in 1966 although the company continued to develop improved designs. Phillips heads were designed to cause the screw driver to cam-out. Cam-out is a process by which a screwdriver slips out of the head of a screw being driven in once the torque needed to drive the screw exceeds a certain amount to prevent overtightening. The term “Phillips” is used in everyday language to refer to any head style with a crossed recess but this useage is not always accurate.

Different types of internal polygon screws/bolts

Type 1: Square head screws

The primary advantage to Square head screws is they are much less prone to “cam-out.” Cam-out refers to the slipping of the bit in the screw head as the screw is driven. The square-head screw was invented by P. I. Robertson, a Canadian, in 1908.

Type 2:Security hex screws

Security hex screws are designed to stop theft and vandalism. A security screw makes it more difficult for the vandal or criminal to get access to their target. ... Tanner is a leading distributor of security screws.

Type 3:Roberston screws

After badly cutting his hand while using a slot-headed screwdriver, Peter Lymburner Robertson invented the square-headed screwdriver and screw in 1908. He received the Canadian patent for his invention in 1909.

Type 4：Double-square screws

Type 5:Hex screws/bolts

A hex “tap” bolt is a term used to describe a fully threaded hex bolt. Many of our customers will use the terms “Hex Tap Bolt” and “Fully Threaded Hex Cap Screw” interchangeably. Remember, that in the U.S., a “bolt” is a fastener that is designed to be used with a nut.

Type 6:Hex socket set screws/allen head screws/cap head screws

In 1919, Dyke defined them as screws that are threaded all the way to the head. A socket cap screw, also known as a socket head capscrew, socket screw, or Allen bolt, is a type of cap screw with a cylindrical head and hexagonal drive hole.

Causes of machine screws thread failure

Screws are widely used in electrical engineering, automobile manufacturing, mechanical equipment, construction and decoration, food and medical machinery, petrochemical industry, shipping equipment, coal mine machinery, aviation instrument manufacturing, transportation facilities, steel furniture and other fields, and are very important products in modern life.

1. The screw has been corroded, and the thread of the screw will fail due to insufficient hardness, so new screws need to be replaced.

2. The combination deformation of screw pulling and torsion is caused, especially the torsion deformation will be twisted and broken when the thread connection is made, so the shear strength of the material is greatly less than the tensile strength.

3. Although the screw is small, it can be used for a wide range of purposes, so that the assembly and installation of any equipment cannot be separated from each other. Therefore, the screw manufacturer reminds you that if you want to use the screw, you need to choose products with good quality to ensure normal operation.

4. Weak separation from base metal and poor bonding force will lead to thread failure, so it is necessary to check whether the connection is correct.

SZQT supplys qualified machine screws,slef tapping screws,nuts,bolts,pins,retaining rings,rivets.