Smiths Tach Reduction Gearbox

[Terry O'Brien]

It seems that there are two versions. The ones I have use a small set
screw to affix the spindle to the shaft on the gearbox. The coupling kit
which is available from Abingdon, Moss etc., comes with a somewhat
larger screw so it will not work on my gearboxes. There may be other
differences which are not so easily apparent.

The result is that I have three perfectly good original Smiths boxes
which are U/S with the currently available coupling kit. Has anyone run
into this problem? Is there a simple solution like having the shaft
drilled and tapped to accept the larger screw and if so to what thread
pattern? When did this change occur? All sugestions much appreciated.
Terry