平行螺紋量規一般的方式是極限式。利用量規的通、止規管理產品螺       紋的極限，保證精確度。極限式量規大致可以分為ISO等級測量方式和以前     的JIS等級測  量方式。以前的JIS測量方式在量規的止端有檢查用和加工       用的區別。ISO測量方  式則沒有這樣的區別，他完 全被簡單化了。測量外      徑用的卡規也是一樣的。具體  使用方法為界限螺紋量規的通規可以輕松穿       過，止規的螺紋擰進不到2圈的話，  這樣測量等級則是合格的。

        In the thread gauges system,the limit type is most common.Thread of     workpiece is ensured by controlling the GO and NOT GO limit.The           types of limit thread gauges systems are broadly divided into ISO             class and conventional JIS class.There were two different types of         conventional JIS gauges,one for inspection and one for production           use.The ISO system is simpler and does not have two types

• ISO等級的美標螺紋，管用平行螺紋用的量規都適用。

      Gauging system for ISO class Metric,Parallel pipe (G)

• GP,GR等用手擰進螺紋，并輕松的穿過。

       Screw this gauge in a worked thread by hand smoothly.GP,GR must go through over the whole length of thread.

• NP,NR等用手擰進螺紋，螺紋擰進多不超過2圈。

       Screw this gauge in a worked thread by hand smoothly by hand NP,NR shall not be screwed in it more than two revolutions from either sides.

• GW,NW等用手擰進的同時，螺紋擰進多不超過一圈。

       GR,NR shall not be screwed in more than one revolution from either sides when screwing this check plug smoothly.