Van Norman Boring bars?????

Cal

The bar has expanding "shoes" that are extended out to center the machine before it is clamped down. The Van Normans have changable "cats paws" they call them, that are different sizes for differing bore sizes. They need these cause the fixed ones have a limited expansion range. My Rottler has three "fingers" that extend out of the bar to center it, handy cause there is no changing "paws" for differing bore sizes. It has the larger diameter bar where this can fit.
 
I can just imagine popping the heads off a SB chevy and dropping the pan. Punching out the cylinders, dropping in new pistons on the cleaned up rods and bolting it all back together with a fresh valve job. Brings a whole new meaning to doing and "Inframe". Probably much quicker than pulling the engine, tearing it completely down, hot tanking, painting, boring, honing, pressing rods, replacing cam bearings, rebuilding the heads and putting it all back together again. I can see at least 10 hours and maybe more just avoiding pulling the engine to begin with. I'm definitely interested in keeping an eye out for one laying around in an old garage or barn somewhere. With all the machine shops closing due to the economy it should be possible to find quite a bit of stuff like that around, here and there.

Bob
 
Rbeckett said:
I can just imagine popping the heads off a SB chevy and dropping the pan. Punching out the cylinders, dropping in new pistons on the cleaned up rods and bolting it all back together with a fresh valve job. Brings a whole new meaning to doing and "Inframe". Probably much quicker than pulling the engine, tearing it completely down, hot tanking, painting, boring, honing, pressing rods, replacing cam bearings, rebuilding the heads and putting it all back together again. I can see at least 10 hours and maybe more just avoiding pulling the engine to begin with. I'm definitely interested in keeping an eye out for one laying around in an old garage or barn somewhere. With all the machine shops closing due to the economy it should be possible to find quite a bit of stuff like that around, here and there.

Bob
Click to expand...

I machined up a mill jig special for V8 flatheads, T's and A's are easy.
 
I did many a boring job in frame on fork lifts. Saved a bundle of cash in tear down time. The 777 was remade by Peterson machine tool and it was called the PK447. The parts would interchange between the 777 and the 447 Peterson is no longer the company it once was and far as I know does not sell the bar any longer. It was identical to the 777 and built in India brought over went through and put an American electric motor on it and went from there. They were very good bars as well. What was nice about the VN bars was they were very compact compared to others. But I can tell you doing an in frame bore was a nut buster without a hoist or something to lift the bar in and out of the frame.

To center the hole you expand the "Paws" in the cylinder center the bar and then clamp it down. Put the cutting tool in and let it rip. Once the paws are below the lip of the cylinder you expand the paws back into the cylinder and has spring tension on them and it stabilizes the cut the rest of the way down. These bars just worked and worked well.
 
I'm still having trouble visualizing this. What expands the paws and how are they kept concentric with the bar?

Cal
 
Cal, at the top of the bar is the knob that expands the Paws into the cylinder. The paws do not rotate only the bottom of the boarding head that holds the cutter holder rotates. The purpose of the Paws is two fold. Center the bar and then stabilize the bar as it goes down the cylinder. The paws expanded into the already board portion of the cylinder keeps the bar from wondering and keeps it strait as the paws drag down the bored section of the cylinder wall. Really a simple effective idea. They were always known as the most accurate of the portable bars.
 
OK, so something like a cone forces the paws out? Are they spring loaded?

If I understand you correctly, the distance from the paws to the bit on the boring bar is constant? As the tool is fed in the paws are also fed down the bore?

I remember reading about building your own boring bar in one of the "Machinist's Bedside Readers". I don't recall that his machine had the centering paws.

Cal
 
Cal,

Having never torn a VN bar apart I am not sure how they expand could be a cone inside but I do not know. The knob at the side on the top of the bar is what advances and retracts the paws. Yes the paws are a fixed constant distance from the rotating cutting head which is the bottom of the bar, and the paws go down the cylinder wall as it is boring the hole. Like I said before the paws serve two purposes. The first is to center the bar and the second is to stabilize the bar as the bar is boring the cylinder.
 
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