The PITCH Command [L]
The PITCH command is used to specify the number of threads per CL unit for the next (and subsequent) COUPLE and THREAD commands. This command is only valid for lathes with threading capabilities. The syntax is as follows:
![\textbf{PITCH /}
\begin{bmatrix}\,\begin{array}{l} \textbf{IPR} \\ \textbf{MMPR} \\ \textbf{PERREV} \\ \textbf{TPI} \end{array} \;, \end{bmatrix}
\,\mathit{pitch} \;
\big[,\textbf{MULTRD},\mathit{starts}\,\big]
\begin{bmatrix} , \begin{pmatrix}\begin{array}{l} \textbf{INCR} \\ \textbf{DECR} \end{array}\end{pmatrix} ,\mathit{value}\, \end{bmatrix}](../../_images/math/32b9b607d2d63bd0fd64205228e7bc58c2c8d950.svg)
If unqualified by a feed modifier, pitch is the number of threads per CL unit. If the CL units are inches then a pitch of 10 indicates 10 threads per inch. The pitch can also be specified as a distance per revolution, or as the number of threads per inch (TPI).
The MULTRD option specifies multiple start threading. The default, if not specified, is 1. The number of starts is coded immediately following the MULTRD keyword. The starts value must be a non-zero, positive integer.
PITCH must be coded before using the COUPLE or THREAD commands. Once coded, the specified pitch and number of starts will be used for all threading operations until a new PITCH command is specified.
The INCR and DECR value option is used to indicate a variable lead thread. It specifies the change of the lead for each spindle revolution. For example, if the pitch at the start is 0.125 and the last pitch is 0.100, the resulting value would be 0.025 (assuming the change in pitch is for 1 revolution). Omit INCR or DECR, or specify a value of zero to indicate a constant lead thread.