This Thread Cutting Values calculator gives you important values needed to cut four common thread forms: Unified National (UN), Acme, Stub Acme, and National Pipe Thread (NPT).

To get the Thread Helix Angle, enter the Threads per inch and Thread Diameter in inches, click "Calculate," and see the Helix Angle on the right. The value is expressed in degrees.

To get the Number of Threading Passes for the four forms, pick the appropriate form box, enter the number of Threads per inch on the left, click "Calculate," and see the results on the right. Only values applicable to that form are allowed.

To get the Diminishing Infeed Per Pass to cut threads, enter the Total Thread Depth, in inches, and the Number of Passes you want to make, click "Calculate," and see the results in the table at the bottom. All values are in inches.

Thread cutting values formulas are courtesy of Iscar Metals Inc., Arlington, TX.