Tr18 × 4 Thread Dimensions

Basic information

Designation

Tr 18 × 4

Thread system

Trapezoidal

Series

trapezoidal

Standard

ISO 2901

Basic profile

Trapezoidal basic profile

Flank angle

30°

Dimensions

Major diameter

18 mm

Pitch

4 mm

Threads per inch

6.35

Pitch diameter

16 mm

Minor diameter (external)

15.5 mm

Minor diameter (internal)

14 mm

Thread depth

2.25 mm

Recommended tap drill

Ø 14 mm

These figures follow the Trapezoidal basic profile of ISO 2901. A 30° trapezoidal profile has a thread height of 0.5 × P: the pitch diameter is d₂ = d − 0.5 × P and the internal minor diameter is D₁ = d − P. The external minor diameter is d₃ = d − 0.5 × P − 2 × ac, where ac is the crest clearance the standard tabulates for that pitch. The recommended tap drill is given as nominal diameter minus pitch, which here is the basic internal minor diameter — a starting point rather than a cutting recommendation.

No specification in this database uses Tr18 × 4. Power threads are not fastener threads — they are found on lead screws, jacks and vice screws, so no bolt or nut in this catalogue is made in this form. The geometry above is what a machinist needs to cut it.

Neighbouring sizes in Trapezoidal.