What is the thread gauge for oversize taps?
The selection of a gauge for oversized taps is incorrect. The gauge is selected according to the "accuracy of the thread" indicated in the drawing instructions. When using an oversize tap, the gauge that should be used depends on the purpose.
Examples of combinations of applications and gauges to be used
(1) Use an oversize tap for pre-plating
⇒ Pre-plating gauge
Before plating, the plating content is considered, and the large processed internal thread is inspected in advance. If you pass with this gauge, you can inspect that it is within the tolerance range of grade 2 + ○○. For a thread angle of 60°, the oversize is 4 times that of plating coating thickness . (If it is a coating thickness of 0.007 mm, it is an oversize of 0.028 mm)
・ Our standard products are available in "2nd grade + 0.03" and "6H + 0.03".
Depending on the coating thickness , a special product is required that reflects the amount of change due to coating thickness in accuracy. (Dopping plating, etc.)
(2) Use of oversize taps to prevent distortion and wear after heat treatment
⇒ Gauge of drawing indication accuracy (2nd grade, 6H)
In this case, what you want to inspect is whether the thread accuracy of the drawing instruction is satisfied, so use the gauge of that thread accuracy.