| 6 편 측 정 |
|---|
|
3 침법(三針法)에 의한 숫나사의 유효경 측정
|
|
|
The so-called “three . wire method” of
measuring pitch diameter, as herein outlined, has been found to be the most generally satisfactory
method when properly carried out, and is recommended for universal use in the direct measurement of
thread plug and thread setting plug gages. The basic pitch diameter is the diameter where the thread thickness is equal to the space between the threads. If the flats at the top and bottom of the thread are the same, the pitch diameter will coincide with the middle of the sloping side of the thread. You may have used a pitch micrometer or a thread ring gage to measure your threads. The thread pitch micrometer is an excellent and easy way to measure threads, but one pitch micrometer will not measure all of the different thread types and sizes. The thread ring gage will tell you whether the thread is right or wrong, but it will not give you an accurate account of the thread depth. The three-wire method is considered to be one of the most accurate and versatile ways of measuring threads. The wires are placed in the threads and a micrometer is used to measure over the top of the wires. Different thread types and thread sizes require different size wires. The "best wire size" can be calculated or looked up in the Machinery's Handbook. The three-wire method of thread measurement can be used for all types of threads including Unified, Acme, and Buttress thread forms.
|
