01-25-2015, 05:34 PM
We have a winner!
Yup, I went with a Ø 0.332" (Letter Q) drill. I did have a GH3 class tap to use, though not my preference in style as it was a high quality HSS 4-flute hand tap.
I used to beat on engineers for putting tap drill size on a print at all. Just give the thread you want and let the machinist determine the right tools to do it with. I sent an e-mail back to the engineer who sent me the print, pointing out that if you actually use the drill specified, your resulting thread does NOT meet the spec for a Class 3 thread with the minor diameter being too large.
Yup, I went with a Ø 0.332" (Letter Q) drill. I did have a GH3 class tap to use, though not my preference in style as it was a high quality HSS 4-flute hand tap.
I used to beat on engineers for putting tap drill size on a print at all. Just give the thread you want and let the machinist determine the right tools to do it with. I sent an e-mail back to the engineer who sent me the print, pointing out that if you actually use the drill specified, your resulting thread does NOT meet the spec for a Class 3 thread with the minor diameter being too large.