List of symbols

Symbol	Name of the symbol	Unit
$ $	trapezoidal thread	$\mathrm{ }$
$D_1$	minor diameter for internal threads	$\mathrm{mm}$
$D_4$	major diameter for internal threads	$\mathrm{mm}$
$H_1$	height of the overlapping	$\mathrm{mm}$
$H_4$	height of internal threads	$\mathrm{mm}$
$P$	pitch	$\mathrm{mm}$
$R_{1max}$	dimension $ R_{1max} $	$\mathrm{mm}$
$R_{2max}$	dimension $ R_{2max} $	$\mathrm{mm}$
$a_c$	clearance on the crest	$\mathrm{mm}$
$d$	major diameter for external thread (nominal diameter)	$\mathrm{mm}$
$d_2$	pitch diameter for external threads	$\mathrm{mm}$
$d_3$	minor diameter for external threads	$\mathrm{mm}$
$h_3$	height of external threads	$\mathrm{mm}$
$z$	dimension $ z $	$\mathrm{mm}$