There are two different approaches to threadcutting in timber.  Particularly for "smaller" threads - say, up to 1" diameter - the easiest and most accurate method is to use a thread box and tap.  These products are similar to the traditional engineer's tap and die, excepting that a thread box has only a single cutting edge.

For larger projects such as box lids, the preferred approach is to cut the threads using a thread "chaser ", of which both internal and external forms are produced - for obvious reasons.  Arm-rests, sizing gauges and thread recess cutters are also produced to assist in the use of these tools.  The proper manipulation of these tools is a test of skill and there are many articles by, in particular, Bill Jones on the subject, mainly taken from the pages of Woodturning magazine, though now also available in book form.  A brief article on the process, by Bill Jones, is inluded in the Crown Tools chaser sets.  In addition, Robert Sorby produce a video showing the process, and Allan Batty has a Masterclass video.

We supply thread chasers from both Crown Tools and Robert Sorby and armrests and other items which tend to make this method easier to carry out. This method is best for threading items such as boxes, on the lathe. NB;  The term "tpi" stands for "Threads Per Inch" and refers to the pitch of the screw threads.  The greater the number of tpi, the finer the thread.  Hence a 12 tpi thread has bigger, coarser threads than a 20 tpi thread.

Don't forget that Allan Batty has a Masterclass video.too, also available on DVD.