by bob adams » Sun Oct 30, 2011 8:27 pm
Yip, 1/4 is too big for most changers, I have seen 1/4" on old MSAs and the likes but not often.
3/16" across the flats is the norm and the internal diameter of the hole is the only difference, most older steels and many current ones use 1/8" pull rods, some later ones (eg. Williams ) use 3/32 If you need to buy rods here the equivalent sizes are 3.2mm or 2.4mm stainless steel .
I would generally run a 4ba or 7ba tap in to the nylon for about 1/8" to give the rod a start but they are meant to cut their own thread.
NB. It is worth noting that the nylon hex is the final part of the chain, The first port of call is the stop (if fitted) at the pedal or lever with the hex sitting just touching the changer finger, set those stops so you just pass the desired note (raise or lower) and only then adjust the hex to fine tune, at that point it should really need backed off rather than tightened further. Most wear on these is caused by players using them as Hillman Minx starting handles.
have fun