I am not sure if the M-9 is a transistorised M-8 or not, this is my first time playing with these, it feels a bit too modern for me!
This is the chart in the owners guide
It uses the adaptor for everything baring 1 7/8. I was actually just measuring the spindle at 3mm dia and was calculating the size of it to get it to 3.75 IPS, and I get I would need a 6mm diameter spindle?
So thanks for the size i will go off and recheck my maths.
It mentions a 15 IPS adaptor as an optional extra
Adrian