Thread Height (Depth)

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Thread height and addendum sketch

Thread Height Definition

The distance between the crest and root is called the thread height. It is designated with hs for external threads and hn for Internal threads. Because in all threads, either the crest or the root must be relieved, the height is a reference dimension and is usually not controlled.

Thread Height Formulas

  • These formulas are valid for 60° symmetrical straight threads (ISO metric and Unified Inch standards)
\( \large h_{n} = h_{s} = \frac {\left (Major Diameter\,-\,Minor Diameter\right )}{2} = \frac {\left (d – d_1\right )}{2} \)
\( \large d_1 = d – \frac{5}{8}\times\sqrt{3} \times P \)
\( \large h_{n} = h_{s} = 0.5\,\times\,\left (d – \frac{5}{8}\times\sqrt{3} \times P \right )= 0.54126588 \times P \)
\( \large h_{n} = h_{s} = \frac {\left (Major Diam.\,-\,Minor Diam. \right )}{2}\)
\( \large = \frac {\left (d – d_1\right )}{2} = \normalsize 0.54126588 \times P\)

As can be seen from the formula, the thread height depends solely on the pitch. Threads with a fine pitch will be more shallow than larger pitch threads, independent of the diamter.

Parameters Dictionary:

  • hn – Internal thread hight.
  • D1Minor diameter of internal thread.
  • D – Major diameter of internal thread.
  • hs – External thread hight.
  • d1 – Minor diameter of external thread.
  • d – Major diameter of external thread.
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