Harold Hall


 Changewheel charts



Two lists are included, one for a lathe having an imperial leadscrew and the other metric. Do though note that in the case of imperial threads the results are given in terms of TPI (threads per inch) and metric threads in terms of pitch (the distance between adjacent turns of the thread)


The values have been taken from a computer program that calculates the result for every possible combination, in excess of 66,000 when 14 different gear sizes are available. From this, the program eliminates those less than 6TPI and greater than 50TPI  resulting in  37,293 combinations being listed.


In the case of metric threads, around 37,000 combinations result from 13 gears with 24162 of these being listed for all the pitches between 0.5mm and 4.0mm.

The permission to copy this is for personal use only  The complete list as presented is though copyright for other uses


Copying / Printing

If you decide to copy the lists for future reference, rather than return to this website, this will have to be done one at a time, naming them, typically, pitch0607, pitch0708, etc. However, if you consider printing them out do bear in mind that a single list is likely to require some 40 to 80 pages, depending on the number of combinations and the size of the font used. For all of the lists we are talking many hundreds of sheets.

Lathe Changewheel combinations

and the thread that results.

Harold Hall



Screw cutting
Metric changewheel combinations
Lathe changewheel combinations