HHG R 級之精度依據ANSI TAP GH 級公差12.7μm(0.005”) 以階段式設定,每一階 段增加12.7μm 小數第1 位4 捨5 入。
HHG R grade system is made by using the datum 12.7μm(0.005inch) in a step form in accordance with ANSI standard, the limits are established by increments of 12.7μm, the upper limit of R grade is decided by rounding off the grade, No x 12.7μm to 1 decimal.

1.上容許度:12.7 μm × N

Upper limit:12.7 μm × N

2.下容許度:上容許度-12.7 μm

Lower limit:12.7 μm × N-12.7 μm

(N=R 級號)

(N=R Number)