Various specifications of thread introduction

According to the different use of thread, fastener thread can be divided into：

1、American Standard Thread

The top and root of the thread are flat, the strength is better, the thread Angle is also 60 degrees, and the specification is expressed by how many teeth per inch. This thread can be divided into coarse teeth (NC), fine teeth (NF), extra fine teeth (NF) three levels. Notation, such as 1/2-10NC, 1/2- outer diameter, 10- tooth per inch, NC- code.

2、Unified Thread

It is jointly developed by the United States, the United Kingdom and Canada, and is the commonly used British thread.

The thread Angle is also 60 degrees, and the specification is expressed by the number of teeth per inch. This thread can be divided into coarse (UNC), fine (UNF), extra fine (UNEF). Notation, such as 1/2-10UNC, 1/2- outside diameter, 10- teeth per inch, UNC- code.

3、Shape V Thread

The top and root are pointed, weak strength, easy to break and not often used. The thread Angle is 60 degrees.

4、Whitworth Thread

British National standard used thread.

The thread Angle is 55 degrees and the symbol is 'W'. Suitable for rolling manufacturing. Notation, such as W1/2-10, 1/2- outer diameter, 10- teeth per inch, W- code.

5、Knuckle Thread

German DIN standard thread.

Suitable for the connection of light bulbs and rubber tubes. The symbol is 'Rd'.

6、Pipe Thread

A thread used to prevent leakage, often used in gas or liquid fittings.

The thread Angle is 55 degrees, which can be divided into straight pipe threads, code-named 'P.S, N.P.S' and inclined pipe threads, code-named 'N.P.T', whose taper is 1:16, that is, 3/4 inch per foot.

7、Square Thread

The transmission efficiency is large, second only to ball threads, and can not be adjusted with nuts after wear, which is its disadvantage. Generally used for vise screw and crane thread.

8、Trapezoidal Thread

Also known as Acme thread.

The transmission efficiency is slightly smaller than that of square thread, but it can be adjusted by nuts after wear. The thread Angle of the metric system is 30 degrees, and the thread Angle of the imperial system is 29 degrees. Generally used as a guide screw for lathes. The symbol is 'Tr'.

Metric trapezoidal thread

Inch trapezoidal thread

9、Buttress Thread

Also known as diagonal thread.

Only applicable to unilateral drive. Such as screw jacks, pressors, etc. The symbol is 'Bu'.

10、Ball thread

Ball thread is the best thread for transmission efficiency, which is difficult to manufacture, extremely high cost, and is used for precision machinery. Such as the guide screw of CNC tool machine.

Representation of imperial bolts：

LH 2H 5/8x3-13UNC-2A

LH- for left thread (RH for right thread, can be omitted)

2N- Double thread

5/8- inch thread, 5/8 OD

3- The bolt length is 3

13- Thread per inch 13 teeth

UNC- Uniform thread coarse teeth

2- grade fit, external thread (3- tight fit; 2- Medium fit; 1- loose fit)

A- External thread (can be omitted, B- internal thread)