The National Pipe Thread or NPT is an American standard for threads on tapered surface.

 

The new NPT features introduced in ThinkDesign are not cylindrical but tapered thread surfaces.

NPT Standard hole

 

 

 

Draft angle is the amount of taper perpendicular to the parting line. This is an important parameter while creating the tapered holes, as it decides the slant and maximum depth of the hole.

 

According to NPT standard, the Draft angle for NPT Hole is 1.79. We need to set the same in Hole Standard Table as shown below.

Note: The value to be set for NPT Hole should be equal to 90 - Draft angle.

 

For a standard tapered hole, the larger  diameter will always be equal to the value of Through/Nominal diameter shown in standard hole table. The smaller diameter is calculated based on the height of the hole and the draft angle.

 

 

NPT Standard threaded hole

 

 

 

The tapered surface for NPT standard thread hole will be similar to NPT standard hole. In case of NPT Threaded hole, the thread will be added to the tapered surface. The pitch of the thread will be as mentioned in the standards.

 

The larger diameter will always be equal to the value of Hole diameter shown in Hole Standard table. The smaller diameter is calculated based on the height and draft angle of the standard.