Machining a 36" diameter bushing.
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  1. #1
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    Default Machining a 36" diameter bushing.

    I was getting some chatter in the bore of this bushing so i had to break out my big boring bar


    20190917_084418.jpg

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    Very cool!!

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    That's pretty spiffy! Is the cutter clamped in a groove like seen in the back end or is it done some other way?

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    Yes there is a groove in each end

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    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).

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    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.

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    Pricey piece of bronze.

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    That's fantastic!

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    Quote Originally Posted by digger doug View Post
    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.

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    Quote Originally Posted by cuttergrinder View Post
    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.

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    There is talk of us getting a vertical boring machine but right now we dont have one.

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    Its a solid bar. It was planed on the side but only half way. Not sure why. That was way before my time. It measures 8 1/2 x 6 x 8' long

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    I know a shop that scrapped a $5000 piece because they were too cheap to make a boring bar.

    Good job!

    What make is your lathe?

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    Quote Originally Posted by Joe Gwinn View Post
    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.

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    Great looking NN Monarch

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    Quote Originally Posted by magneticanomaly View Post
    I know a shop that scrapped a $5000 piece because they were too cheap to make a boring bar.

    Good job!

    What make is your lathe?
    Its a a monarch NN i believe

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    Quote Originally Posted by cuttergrinder View Post
    There is talk of us getting a vertical boring machine but right now we dont have one.
    1. The ease (and safety) of loading/unloading, increased productivity.
    2. The much increased production from the side head.
    3. The increased rigidity allowing heavier cuts.

    should easily justify one.

    Vertical Turret Lathes | O'Connell Machinery Co, Inc.

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    Quote Originally Posted by Milland View Post
    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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    Quote Originally Posted by johnoder View Post
    Great looking NN Monarch
    I believe I see a lever for a powered compound as well. Nice feature.

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    Quote Originally Posted by Cole2534 View Post
    I believe I see a lever for a powered compound as well. Nice feature.
    Its not a powered compound. It has a rapid traverse on the carriage. Its actually a cable drum lathe. It cuts leads rather than threads per inch.


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