Lookfor the 1.00 mm pitch in the chart's first column. Match this row to the 65% thread percentage column. The result is 0.8444. Subtract the result from the thread diameter (4.0 mm) The result is 4.0 mm - 0.8444 mm = 3.1666 mm, which is the necessary diameter for the drilled hole.
FromStandard Sets. Once you know your wire diameter, you need to find out what is the premissable Measurement for your pitch diameter (Depending on the class). Use our Over Wire Calculator to find out! 1 NPT : Basic Thread Dimensions (Pitch, minor & major diameters, depth, lead), Tolerance range for all applicable classes and much more.
Rightsize drill for 1/8″ NPT: The appropriate drill bit size for a 1/8″ NPT pipe tap is designated as an R type, which corresponds to 0.339″ or approximately 8.6mm. National Pipe Taper (NPT): NPT, or National Pipe Taper, is a U.S.standard for tapered threads on hollow pipes and fittings.

The1/8″ NPT tap’s diameter is not 0.125 inches, but based on the thread on the end of a 1/8-inch pipe, it’s approximately 0.405 inches in the “big” diameter. Now, for the drill bit size, the secret lies in subtracting the pitch of the thread from its diameter. For a 1/8″ NPT tap, the magic letter is an R-shaped drill bit.

NationalStandard Taper Pipe (NPT) Threads Size Chart 1/16 0.3125 27 0.16 0.2611 1/8 0.405 27 0.18 4½ 2½ 0.26 1/4 0.54 18 0.2 4 3 0.401 3/8 0.675 18 0.24 4½ 3 0.408
nominalper of of overall taper regular taper regular drill size inch flutes threads length regular (dryseal) regular (dryseal) sizes npt nptf nptt nptft 1/16 27 4 11/16 2-1/8 18.66 18.66 33.26 33.26 “c” interrrupted and straight thread 1/16" to 2"
. 230 206 209 32 69 384 325 246 66

1 2 npt thread drill size