1/4 - 20 UNC : Basic Thread Dimensions (Pitch, minor & major diameters, depth, lead), Tolerance range for all applicable classes and much more

For example, 1/4-20 means a thread with a pitch of 20 TPI (1/20=0.05″). It is also allowed to denote the pitch by distance. For example, 1/4-0.05P means a thread with a pitch of 0.05″ (same as 20 TPI).

1 1/4 - 20 20-UN : Basic Thread Dimensions (Pitch, minor & major diameters, depth, lead), Tolerance range for all applicable classes and much more

1 - 20 UNEF : Basic Thread Dimensions (Pitch, minor & major diameters, depth, lead), Tolerance range for all applicable classes and much more

1/4-20 BSW : Whitworth Thread Dimensions and Tolerances. All the relevant data for this tread in one spot

1/4 - 20 UNC : Grundlegende Gewindemaße (Steigung, Kern- und Flankendurchmesser, Tiefe, Winkel), Toleranzbereich für alle anwendbaren Klassen und vieles mehr

With our Calculator and Chart , you can get the precise tap drill size as a function of the thread height. Calculation Examples. Calculating Tap Drill Size for M8 X 1.25 (Metric Thread)

The major diameter of a thread is the diameter of an imaginary cylinder that touches the largest diameter of a thread. The nominal value of the major diameter equals the nominal thread size. For example, in a UNC 1/4-20 thread, the nominal major diameter is 1/4" (6.35 mm)

The Ulitmate ACME Thread Resource: Basic Dimensions, Classes, Tolerances, Formulas, Charts, and Explanations

BSPP G 1/4 : Brith Pipe (BSP) Thread Dimensions and Tolerances. All the relevant data for this tread in one spot