Actually, just noticed mine is the M4/3 and not the mb4 (b=bench) or mf4 (f=floor). There's a photo on Tony's website somewhere that show a gang of these drills ( or an earlier model) mounted to a long cast iron bench.This is an mb4 , yours shows mb4/3must be the difference between them , I see the lifting mechanism ! I would say it's a good 80mm , I will measure tomorrow