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Machining a 36" diameter bushing.

Lad, you should have made the bar from rubber for extra energy absorption.

(More seriously, I'd have swapped the compound for an additional solid riser. Or even bolted the bar to the existing riser, used an angle-ground bit, and done the math for diameter corrections).
 
That job would be much better on a Bullard, a Dynatrol one at that.

done many jobs like that, and while the end turret is doing the I.D.
the side head can be turning the O.D. or facing.
 
That job would be much better on a Bullard, a Dynatrol one at that.

done many jobs like that, and while the end turret is doing the I.D.
the side head can be turning the O.D. or facing.


Sure, but who can go get just the right machine for every job? The man has a fine solution for his needs and the result will be as good as required.
 
I was getting some chatter in the bore of this bushing so i had to break out my big boring bar

Is that bar a solid square cross-section, or is it two rectangles bolted together? It looks like two rectangles.

The reason to ask is that two rectangles bolted together have 1/8 the bending stiffness of a solid square of the same outside dimensions.
 
The reason to ask is that two rectangles bolted together have 1/8 the bending stiffness of a solid square of the same outside dimensions.

Hi Joe,
OP's already stated it's a solid bar, but I'm curious about the "1/8th" statement. I'd agree if they were just stacked together they'd be significantly less stiff, but truly bolted together (not just in the middle) I think they'd be much closer to the solid value.

As well, might even have a damping advantage with the two faces rubbing together helping to convert some vibration into heat. But there might be a geometry drift due to that heat, so perhaps a bit of a gamble.
 
Hi Joe,
OP's already stated it's a solid bar, but I'm curious about the "1/8th" statement. I'd agree if they were just stacked together they'd be significantly less stiff, but truly bolted together (not just in the middle) I think they'd be much closer to the solid value.

As well, might even have a damping advantage with the two faces rubbing together helping to convert some vibration into heat. But there might be a geometry drift due to that heat, so perhaps a bit of a gamble.

I'd agree - stiffness would be a function of clamping forces and surface roughness. For example, imagine two bars with 1/4" deep 60° Vee cuts on each face, cuts that mated perfectly. Then use a patttern of bolts or rivets that hold the bars together with immense force. Maybe not the same modulus as solid, but pretty close I'll bet. The old riveted box beams and such were made to be pretty stiff.

Not sure how much heat would be generated, or what the geometry effect would be. The tighter that they were bolted together, the less heat I guess.
 








 
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