Machining a 36" diameter bushing. - Page 4
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  1. #61
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    Quote Originally Posted by cuttergrinder View Post
    We didnt make the mics. Im not sure who manucatured them. These are not the mics i used on the bushing. Just a picture i had on my phone. I dont think this picture was even the biggest ones.
    No, I mean to keep both ends of the mic aligned to the center of a large work piece, so you know you're getting the true diameter.

    I figured that was just a picture you had handy, since you'd be really tall if 54" didn't even come up to your armpit

  2. #62
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    Quote Originally Posted by BoxcarPete View Post
    No, I mean to keep both ends of the mic aligned to the center of a large work piece, so you know you're getting the true diameter.

    I figured that was just a picture you had handy, since you'd be really tall if 54" didn't even come up to your armpit
    Its just like any other mics. You just wiggle it around to find the sweet spot. Thats my son in that picture. He is 6' 3" tall i am 6' 6"

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    Quote Originally Posted by Bill D View Post
    Out of interest, how do you measure the diameter that accurately. Do you have some really big micrometers or what?
    FYI
    The other option for large diameters are Pi tapes. ref PI Tape ®

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    Quote Originally Posted by Limy Sami View Post
    FYI
    The other option for large diameters are Pi tapes. ref PI Tape ®
    Dang it !...Double Dang it !
    Attached Thumbnails Attached Thumbnails bloomcounty-blasphemer.jpg  

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    Brings back memories. I have done similar jobs on a big Axelson. We usually were cutting steel. Often, we needed to hang a big weight on the outer end of our boring bar. Our bar was made of 6' round instead of flat stock. Thanks for posting.

    JH

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    Quote Originally Posted by digger doug View Post
    Dang it !...Double Dang it !
    Is that a pi tape he is tied to the tree with?

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    Quote Originally Posted by Rob F. View Post
    Is that a pi tape he is tied to the tree with?
    I keep one handy for just such occasions......

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    Quote Originally Posted by Pariel View Post
    This also assumes that the deflection is not high enough that the second beam is under load. The complexity of the interaction if they're not attached makes for a fun analysis problem or a pain in the butt depending on your feelings about the work.
    Typically, the two half-bars would be bolted together in some optimum manner, so the two half-bars would not be independent, they would be sharing load. The key question is how well that works in practice.

    Attaching the beams at the end using almost any method will put the setup a lot closer to the original value than the 1/8 value.
    At the expense of increasing the shear load on those few bolts.

    Now, this would kind of beg the question of why someone would design it using two separate bars, but as neither OP's work nor anyone else as far as I know has, I think we can just close the case on it.
    As you say, nobody seems to make a composite boring bar, and it's probably because just making the bar solid is easier and more effective.

    What are common is hollow bars with anti-vibration dampers within.

    I have fabricated box beams from wood (to hold a grill to a deck, with the grill out over dirt), and it was essential to epoxy the four hardwood planks to one another. All the screws did was to hold the assembly together until the epoxy cured. Screws alone were floppy - the wood was able to slide ever so slightly.

  9. #69
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    Quote Originally Posted by jccaclimber View Post
    Fully admitting that I'm just throwing fuel on the fire here. Why not move to torque+angle if you're going to go that far? A snap off tang can do a good job of maintaining desired torque, but torque carries a less than ideal correlation to installed fastener tension.
    The reason to mention this kind of bolt was to show the limiting case in practice. It's pretty heroic. We did have the snap-off tang variety, but as you say the correlation to clamping force is approximately proportional. So, one clamps harder, or uses more bolts.

    By the way, I did find my notes - we used ASTM A490 bolts, which are mentioned in the same ASTM standard as A325. This standard has a section on the need to keep all paint off of faying surfaces that are supposed to transfer shear loads by friction when clamped.


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