Originally Posted by
tonyfoale
Actually, the adaptor drawing is not mine, I found it on the net and it was designed to be used with a cordless drill. For me it was just a nice reference for the dimensions of the Bridgeport dogs...
I would highly recommend some form of counter balancing the weight of the knee and table. It is a win/win modification. For a small mill I'd use an actual counter weight with a cable over a pulley, that enables you to exactly balance the weight throughout the movement range making moving the knee assembly effortless whether manual or motorized. It is easy enough to cast a concrete lump for the counterweight, throw in any steel or lead scrap to reduce the needed size. I use counter weights on a couple of drill presses which don't have a rack and pinion. However, that is hardly practical with mills of the Bridgeport's size, hence my use of the pneumatic spring units which give reduced help as they become extended (table raised), but owt's better than nowt.