Thread form tap chart series#

For example: 3/4– 0.0625 P – 0.1875 L UNF denotes a 3/4″ UNF thread with 3 starts. For a multiple-start thread, the lead is also indicated. Number of Starts: By default, all threads have a single start.For a left-hand thread, add the suffix -LH. Direction: By default, the thread is right-hand.For a detailed explanation of classes, read the dedicated section below.1=Tight fit, 2=Medium fit, and 3=Loose fit. The first character is a digit between 1 and 3.

The class is defined by a two-character code.

The pitch remains the same for the whole diameter range in these series.

ASTM B1.1, also defines several constant pitch series.

Thread form tap chart series#

In most cases, the series will be UN C, UN F, or UN EF (Coarse, Fine, or Extra fine pitch).For example, 1/4-0.05P means a thread with a pitch of 0.05″ (same as 20 TPI).

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