ADS Environmental Services Model 4000 530017 A0 - Manual (Page 61)

3-38 ADS Model 4000 Manual
Drilling the hole in the manhole rim
4. Use a 3/8-inch (9-mm) x 16 threads-per-inch tap to cut threads
in the hole. Twist the tap clockwise ¾ turn, and then back out
½ turn before continuing deeper.
Using the tap to thread the hole
5. Chase the threading action at intervals to clear the metal debris
by backing the tap almost completely out of the hole and then