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How To Distinguish Different Threads?
Apr 11, 2017

        Are you often troubled with different threads? G3/8?1/4NPT? R1/8? UNF? KF16? Then below let me introduce different threads and tell you how to distinguish!

International Metric Thread System : Chinese standard CNS adopts this kind of thread.Thread top is flat,and easy to lathe, thread bottom is round so as to enhance the strength of threads. Thread angle is 60°,Specification is shown in M.Metric thread are of two kind: coarse thread and fine thread.Shown as M8*1.25(M is code, 8: nominal diameter, 1.25: thread distance)

International Metric Thread System.jpg

American Standard Thread: Top and bottom are both flat, with good strength.Thread angle is 60°,specification is shown as "how many threads every inch".It is classified as NC, NF, NEF shown as 1/2-10 NC.(1/2:outer diameter; 10:number of threads every inch; NC: code)

American Standard Thread.jpg

Unified Thread:Edited by America,England,and Canada,and currently recognized as inch screw thread. Thread angle is also 60°.Specification is shown as "how many threads every inch". It can be classified as UNC, UNF and UNEF. Writen as 1/2-10UNC(1/2: outer diameter;10: number of threads every inch;UNC:code)

Sharp V thread:Top and bottom of thread are both sharp,and the strength is relatively weak,and easy to be broken, so not often used. Thread angle is also 60°.

Sharp V thread.jpg

Whitworth Thread: The standard is adopted by England.Thread angle is 55°,shown in code "W".Applicable for rolling process. Written as W1/2-10.(1/2:outer diameter; 10:number of threads every inch; W: code)

Whitworth Thread.jpg

Knuckle Thread:Specified by German DIN,and application for bulb, rubber hoses.Mark code is"Rd"

Knuckle Thread.jpg

Pipe Thread:The thread used for preventing the leakage, commonly used for the pipe connection of gas or liquid.Straight pipe thread is"P.S,N.P.S" and inclined pipe code"N.P.T", and tapered degree: 1:16, that is 3/4".

Pipe Thread.jpg

Square Thread: Transmission efficiency is high, second to the ball type thread, but it can not be adjusted by the nut,and this is the disadvantage.Commonly used for vice screw and cranes.

Square Thread.jpg

Trapezoidal Thread: called as ACME,and the transmission efficiency is lower than square thread, but it can be adjusted by the nuts after wearance. Metric thread angle is 30°,Inch Thread is 29°,and commonly used for driving screw of the lathe. Written as “Tr”.

Trapezoidal Thread.jpg

Buttress Thread:called as inclined square thread, and only applicable for single direction transmission, like Screw type lifting jack, press machine,etc.Written as "Bu"

Buttress Thread.jpg

Size of inch threads, usually shown by "number of threads each inch",which is equal to the pitch reciprocal. For example, 8 threads every inch,that is the thread distance is 1/8".

Size of inch threads.jpg

For more information, welcome to inquiry me. All of your questions shall be treated in priority.