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  • Long bolts drilled through.

    How in the world do they drill such small holes , about 1/16, length ways through a 7 or 8 inch bolt?????

  • #2
    VERY carefully! High rpms and move the drill bit in and out advancing a little bit each stroke. Too much swarf or turnings in the lands will grab the bit and snap it!

    Or maybe they are using EDM?

    mark61

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    • #3
      It depends on what they are used for but a "hole popper edm" could do it very fast and accurately. They have a rotating electrode in a spindle assembly that moves up and down to drill the hole, and the hole is flushed with fluid of some sort.
      Jonathan P.

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      • #4
        Mark61 and Jonathon,
        These bolts are from about 1959, I am not sure EDM was even known of at that time. The only other option I could conceive of was drilling also, but that seems so unrealistic. I do know that they were a NAS bolt modified by the factory, today at $200 per pop I was looking for alternatives

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        • #5
          There are some odd single-flute drills used for deep holes. Pecking and high pressure coolant were probably used.

          The holes are 1/16? What's the shank size?

          If the shank is over, say, 3/8", the hole wouldn't be for lightening. It would probably be so the installer could drop a long micrometer probe down there to measure stretch.

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          • #6
            Thats why they are $200 each. would probably be more now.
            Every Mans Work Is A Portrait of Him Self
            http://sites.google.com/site/machinistsite/TWO-BUDDIES
            http://s178.photobucket.com/user/lan...?sort=3&page=1

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            • #7
              Micro drilling

              Ken.

              I'd guess that at that age "micro-drilling" would have been used.

              Try some of these links as they are a good read:
              http://www.google.com.au/search?hl=e...e+Search&meta=

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              • #8
                Carbide gun drills and 1,000psi coolant running 12,000rpm and a feed pressure rated in grams.
                I just need one more tool,just one!

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                • #9
                  TRX,
                  Shank is 5/8, the hole is for lube with a grease fitting at each end.
                  The hole diameter is a guess as I have not removed any of the fittings, I was suspecting it to be the same size as a perpendicular hole in the center to lube the center bearing which is about 1/16.

                  Ken

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                  • #10
                    Lane,
                    I really did not consider the $200 (current price) at all out of line, but still they add up to a lot of money, that is why the search for an alternative, which does not look promising, I would guess the NAS close tollerance bolt alone would cost $60 - $70 each

                    OT, thanks, I will check that out just for the info.

                    wierdscience, well, I dont have one of those handy

                    Ken

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                    • #11
                      try these folks:
                      http://www.gen-aircraft-hardware.com/default.asp

                      Ken, what are you working on? Do the bolts really need to be in the 7" to 8" range? I have drilled and tapped grease holes(passages) for use in torque link applications, but not 7 or 8 inches.
                      Last edited by Jim Caudill; 05-26-2008, 11:33 PM.

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                      • #12
                        "NAS" job?

                        If it is a "NAS" job will it not require certification? If not a "NAS" job and you require NAS bolt specs, are you really limited to the existing hole size? Why drilled right through with a grease nipple on each end?

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                        • #13
                          A landing gear swivel bolt? My Archer had a long through-drilled bolt about 5/8" holding the main landing gear scissors assembly togther. Yep, about $200 each.

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                          • #14
                            Originally posted by Ken_Shea
                            TRX,
                            Shank is 5/8, the hole is for lube with a grease fitting at each end.
                            The hole diameter is a guess as I have not removed any of the fittings, I was suspecting it to be the same size as a perpendicular hole in the center to lube the center bearing which is about 1/16.

                            Ken
                            Yuk,I hate those.I'm assuming they have a good reason for using that design.I always prefer the grease zerks in the bushing and not the bolt.Are the bolts timed so the cross hole ends up in the neutral axis I hope?
                            I just need one more tool,just one!

                            Comment


                            • #15
                              OT,
                              Yes, to be FAA legal these these bolts do require FAA certs, but it is an old aircraft and some wiggle room is available, likely not these though as they are still available from the factory. The main cost is obviously the result of the modification.

                              Three bolts are required, they are the main rotor blade clevis bolts that attach through the rotor hub. Each clevis has three bearings, one at each end and a center bearing, these bearings require lube and with the design I see no way of doing that apart from the mentioned bolts.

                              wierdscience,
                              Yes they are timed at 180 degrees permitting the rotation of the bearings at 600 hours and replacement at 1200.

                              If I could find an accurate and reliable way to put a hole through these I would do it in a heart beat, unfortunately, at this point is just does not seem possible.

                              Jim, that is a good link, and I will sure check them out.
                              Just measured it and overal length undJer head is 7 inches.


                              Ken
                              Last edited by Ken_Shea; 05-27-2008, 12:17 AM.

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