Helicoil Tapping Chart helicoil heli-coilThe minimum tapping depths shown below (Dimension H) are the MINIMUM for countersunk holes and insert set-down of 1-12 pitch maximum. The calculation for Dimension H is:H is equal to insert nominal length +1 Pitch.The tapped hole must be held within the stated pitch diameter limits for the required class of fit for the installed Heli-Coil insert.When anodize, Iridite or other finishes are used, all tapped hole dimensions must be met after the finishes are applied.