On Monday, April 8, 2013 at 3:18:02 PM UTC-5, John M wrote:
The fixed cast iron nut on the screw drive of my Columbian cast iron vise has
broken off & is lost now....What is the best repair?


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I have a Columbian 203-1/2 vise that had a main/spindle nut that was completely broken in 2 (obviously from someone torquing it down with a cheater bar or sledgehammer judging by the bent handle). I didn't want to spend the money ($85) to have a welder attempt to fix it so I tried JB Weld, which of course immediately re-broke when I tightened it back down. But it gave me a clean break that I then used super glue on (just to hold it together while drilling). I flipped the spindle nut over upside down in a drill press vise and I drilled (4) 1-1/2" deep holes (5/32 drill bit), spaced about 1/2" apart along the length of the main nut, down through the bottom and through the crack/break. I then tapped the 4 holes with a 10-32 tap. I screwed in 4 10-32 x 2" screws as far as I could with vise grips until they broke off. I grinded down the remainder of the screws flat with the base of the main nut. It seems to hold well, and I've cranked down hard on it. It definitely increased the shear strength... probably much more than any surface braze/weld could have done. If it happens to break again I'll re-drill and re-tap (4) 1/4-20 x 1-1/2" bolts up from the bottom which will give it even more shear strength than the 10-32 screws I used.