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Deep Hole Drilling Revisited

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  • Deep Hole Drilling Revisited

    I know that deep hole drilling has been flogged plenty here. I'm going to drill a 0.500" hole 8.5" deep in a piece of round bar on my lathe. The only long drill I can locate locally is a 12" aircraft drill with 2" flute length. If I peck drill about 1/8" per peck, will this drill work?

    Would I be just as well off to use a 1/2" drill with a 1/4" shank pressed/pinned into a piece of drill rod to extend the length?

    I know I can order all kinds of drills, but I don't think I need to make this overly complex.

    Lynn S.

  • #2
    For deep holes, I generally go about 0.050" per "peck" before clearing chips, but you might be able to do more. Just proceed cautiously and see how much the flutes fill up. Then you'll know how often you need to clear the chips. I don't see why the 12" aircraft drill won't work, it will just be tedious.

    A 1/2" drill extended with a 1/4" shank might tend to twist on you, so a 3/8" shank extension might be better. The key there would be to be sure everything is concentric. If you can just buy the 12" drill though, that's probably easier.
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    • #3
      Just out of curiousity, what material, and how large is your O.D.?
      Paying Attention Is Not That Expensive.


      • #4
        12L14, OD is 1.5".
        Lynn S.


        • #5
          Is there any way you could mount a drill press head on the lathe and use that? Seems to me that would be easier. Much like doing deep holes on a Horizontal Boring Bar. Just an idea
          Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


          • #6
            Well, the alloy and O.D. rules out (I think anyways) of suggesting DOM tubing. Though it might be available. I do not know if 12L14 is available in DOM, or with a wall that thick.

            I would be leery of trying to drill a hole that deep with a drill of only 2" flute length. That is a lot of drill shank to be buried deep inside of a hole you are drilling. The last thing I'm reatively sure you would want is for the work to gall up on the shank and break the drill off deep into your work.

            Yes, you can order all kinds of drills, just so happens I was looking for some. I had out the MSC catalog. They offer several 1/2" taper shank drills with flutes of approx. 8, 10, 13 and 18". Unless you've already bought the "local" drill, it seems you would be buying one anyway. IMO, they, (at least a 1/2" one) are not "that" expensive. Sure, you may never use it again, but....

            For the price of a drill with sufficient flute length, IMO, buying that drill, to fit your need wouldn't be overly complex.

            I'm not trying to spend your money, just offering a suggestion/opinion FWIW.
            Last edited by ERBenoit; 03-19-2007, 02:10 PM.
            Paying Attention Is Not That Expensive.


            • #7
              I have drilled holes that size on a several occasions with no problems. 12L14 is definitely in your favor.

              If I have a suitable aircraft or other long drill available, I use that, otherwise, I weld or silver solder an extension to a standard bit.

              Start the hole with a regular jobber length drill full depth, then switch to the extended drill. I peck a diameter or less at a time and pull the drill out fully to clear chips. I prefer sulfur cutting oil, but any cutting oil will be better than none. It does not hurt at all to use shop air to clear chips with the drill out. Use proper eye protection of course.
              Jim H.


              • #8
                Thanks, guys. I think I can probably get there with the aircraft drill with 4" flute length. I'll drill to the max depth with a jobber, and then switch over to the long one. It will be a lot of pecking, but I'll get there.
                Lynn S.


                • #9
                  If you're drilling a barrel for a scale model cannon barrel, I've made 4 or 5 of them using the aircraft type drill bit, by lubeing well, and clearing chips often.


                  • #10
                    Get a long Parabolic drill from MSC the are the cats meow for long holes I have one 3/8 by 12 inchs i use all the time for deep holes they dont load up with chips because of the fast spiral it will eat a 8 1/2 inch hole right up about ten minutes to drill no problem.
                    Every Mans Work Is A Portrait of Him Self