With a slight groan, the bolt holding the rear jaw sheared off, and the bottom casting broke behind the jaw.
	Here's a crack visible on the other side.
	Once I took the vise apart and unscrewed the remaining back jaw fixing bolt, I could lift off the other broken part of the casting.
	"Step A" was to align the vise on my milling machine table, and mill the broken area straight across to clean up the damage and prepare a surface for some reinforcement.
	A quick touch with a lefty drill and the broken bolt spun right out.   As you can see from the photo, I kept the key in the back jaw so I could use it to retain good alignment of the back jaw as I rebuilt the vise.
	Seeing what weenie little bolts held the back jaw in the first place, I decided to beef up that bit of underachieving hardware.  So, I drilled the back jaw for some new bolts that I planned to run down through into the casting below. I figured I'd better countersink the bolts at least partially to make sure they'd be below the upper surface of the vise jaws.
	I turned the bolt heads down because there was not enough clearance behind the vertical jaw section for the big bolts I wanted to use.
	I held the back jaw in place to mark the location for my new screw holes.  Note that I retained the key in the back jaw so I could index it back where it belonged in the base.
	I drilled and tapped the base for my new screws.
	Since I figured on bolting my reinforcement straight across the back of the vise, I'd have to shorten the lower section of the moveable jaw, so I ran the jaw past the closing point, and marked what I'd need to cut off.
	My little gravity powered bandsaw rig made short work of the cut.
	Looking around the shop, I found a nice bit of cold rolled 1018 steel to use for my reinforcement, and I squared up the block.
	On the drill press, I countersunk four screw holes for bolts I could sink into the end of the bottom vise casting.
	Clamping the piece in place, I simply drilled through the clearance holes with the appropriate tap drills
	and hand tapped right through the holes to be certain everything would line up nicely.
	After screwing the reinforcement securely and permanently in place with some red Loctite, I set the vise back on the mill and milled the top surface exactly level with the ground top surface of the bottom casting. I left a bit sticking up at the back edge for extra support of the fixed jaw.
	Then, I carefully widened what was left of the key slot to accept the key from the back jaw.
	A few trial fits,
	A few light cleanup passes, and I got that back jaw to fit tightly in place.
	Now, with the big hold-down bolts and my rear reinforcement, I'm counting on this vise to keep on squeezing!

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