Announcement

Collapse
No announcement yet.

Drilling a really long hole

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Drilling a really long hole

    Hi-I was asked yesterday if I could rifle drill a .875" hole lengthwise through the center of a 4.5" shaft that is 110" long, and keep an accurate center. I have been thinking about this, and am not sure. I have a lathe with a stretch bed, and can get about 160"+ between centers, and have a couple good steady rests, but am not sure about the procedure. Using a small gun tap with air or oil to start, then going up in size would be theoretically possible. The finish doesn't have to be perfect because it only carrys air, but the center would have to be pretty precise. Has anyone else tried to do this? This job may not materialize because of the expense, but now I would like to know if this is possible-Thanks, Rolland Christians (Oh, by the way, I just joined this group yesterday-I have a small machine shop in North Florida, and take on some pretty strange projects for people. Used to be a machinist for Ford in Mn. a long time ago)

  • #2
    Seems to me that if it only carries air and not bullets or similar then the requirement for accurate centering applies only to the ends. Not so?
    Free software for calculating bolt circles and similar: Click Here

    Comment


    • #3
      Originally posted by Rolland-Christians
      I have a small machine shop in North Florida, and take on some pretty strange projects for people.
      North Florida = ...strange people for projects. (I was born in Ocala.)

      Welcome, this is a great group here.
      Dan from Raleigh, NC

      If it's stupid but it works, it's not stupid.
      _____________________
      "What is your host's purpose for the party? Surely not for you to enjoy yourself; if that were their sole purpose, they'd have sent champagne and women over to your place by taxi." P.J. O'Rourke

      Comment


      • #4
        If it only carrys air, why are you not just buying premade hose/tube that can handle the pressure/tempature required?
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

        Comment


        • #5
          Originally posted by Rolland-Christians
          Hi-I was asked yesterday if I could rifle drill a .875" hole lengthwise through the center of a 4.5" shaft that is 110" long, and keep an accurate center. .................................................. Used to be a machinist for Ford in Mn. a long time ago)
          Sounds like a tall order without a real gun-drilling setup. It can be done, it was done by the hundreds per day in WW2.

          A machinist in MN? Would that be the Highland plant? Down by the "Ford bridge" in St Paul? Used to go by there all the time. Even had a tour of it ages ago.
          1601

          Keep eye on ball.
          Hashim Khan

          Comment


          • #6
            Thats a perfect job for a gundriller
            To them its a piece of cake and a two hour job
            Rich
            Green Bay, WI

            Comment


            • #7
              Welcome Rolland

              gun drill schmun drill. If you look at post 19 in this thread, it went by without fanfar but in it I explained a technique that is almost foolproof using standard drills and reamers....the original story came with the claim of holding a thou over 3 or 4' with a 3/4" hole. Having used it, I believe it just might be that good (i haven't drilled 4') so depending on your view of 'accurate' this will probably work.

              http://bbs.homeshopmachinist.net/showthread.php?t=43014
              in Toronto Ontario - where are you?

              Comment


              • #8
                Thanks, it only carries air, but also is the main driveshaft and turns a large fan using a 1200HP cat engine-The air is for the air clutch. It should be concentric to maintain balance of the shaft. I bought my bridgeport and Ajax lathes from a machine shop that went out of business a couple years ago in Ocala Fl-The plant in Mn was at Eveleth, worked in the Fairlane and Thunderbird plants (Taconite processing plants, worked as a field millwright, plant millwright, and machinist-Untill they laid me off for the last time in 1981, so I moved to Florida)Worked for McGraw Edison as a machinist in Ft Lauderdale for awhile in the early eighties, and then someone bought the shop and broke it up, sold the land, and told us to go find another job-Did a lot of portable boring for them, under all the drawbridges in Fort Lauderdale, re-bored and re bushed the machinery underneath, one side at a time, and they would open the other side to let the boats through.

                Comment


                • #9
                  Originally posted by Mcgyver
                  Welcome Rolland

                  gun drill schmun drill. If you look at post 19 in this thread, it went by without fanfar but in it I explained a technique that is almost foolproof using standard drills and reamers....the original story came with the claim of holding a thou over 3 or 4' with a 3/4" hole. Having used it, I believe it just might be that good (i haven't drilled 4') so depending on your view of 'accurate' this will probably work.
                  Well, since you are in a "metric country, you wouldn't know this ( ), but that hole he wants is apparently 9 feet and 2" long.....or about 2.8 m.

                  much of the problem is getting a machine to swing that length of shafting, while manipulating a drill of some sort which is the same length plus a bit.

                  If you have to pull out the bit for any reason, it's gonna be a pain. Oil out the drill tip would take care of the chip issue.

                  That 160" bed is going to result in only about 40" or a bit more of clear space, so some sort of clamp holder that a long drill slides through, or a slide bearing arrangement and an external frame to steady the drill rod and guide it down the center may be necessary.

                  or a gun drilling setup, which is about that to begin with. You will "make" a gun drill setup to do the job, essentially.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Seems to me that thick wall pipe would serve just as well.
                    Free software for calculating bolt circles and similar: Click Here

                    Comment


                    • #11
                      Seems to me that thick wall pipe would serve just as well.
                      Or at least be a good place to start.

                      Comment


                      • #12
                        I did a quick calculation of the bending strength of a solid bar that size vs a pipe with 0.5 inch wall thickness.

                        The solid bar with simple supports at each end and with a 2000 lb distributed load located evenly starting 20 inches from each end will produce a static deflection of 0.111" at the centre.

                        The 1/2 inch wall pipe with the same loading deflects an additional 0.075".

                        All that is required is a couple of end caps and a few spiders tacked to a suitable piece of air pipe that runs down the centre of the main shaft pipe. Seamless DOM should suffice for the shaft just fine.

                        It will also weigh half as much which will make the stiffness to mass ratio higher.
                        Last edited by Evan; 09-02-2010, 11:50 PM.
                        Free software for calculating bolt circles and similar: Click Here

                        Comment


                        • #13
                          Unless I am unable to read today, the part is a SHAFT, which probably needs little in bending, and plenty in torque capability.

                          However, the issue is not the design, he apparently has been told that, and much more how that hole is getting down it.

                          That having been said, a 1200 HP Cat diesel, and a large fan..... I don't think that is a good place to have a rough, and particularly not a "scored" inside diameter. Torque-wise vibrations might cause those scores to become stress raisers, and lead to a fracture. With a 1200HP fan, that is probably not a good idea, it makes a spun-off chuck in the shop seem like a dropped nail paring.......

                          So half-way methods are not the very best here..... Someone with a 25' bed machine could deal with it in short order, especially if they have an oil-fed drill. Not all jobs that darken the door are ones you want. or that you should do.
                          1601

                          Keep eye on ball.
                          Hashim Khan

                          Comment


                          • #14
                            Unless I am unable to read today, the part is a SHAFT, which probably needs little in bending, and plenty in torque capability.
                            No kidding? The point is to show how little the core contributes to the strength. The torque capability will be directly proportional to the bending strength, which is what I have a program to calculate.
                            Free software for calculating bolt circles and similar: Click Here

                            Comment


                            • #15
                              I'm confused, are you saying Ford made their own steel up there?

                              Originally posted by Rolland-Christians
                              <snip>...The plant in Mn was at Eveleth, worked in the Fairlane and Thunderbird plants (Taconite processing plants, ...

                              Comment

                              Working...
                              X