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Gun drilling 1.010"

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  • Gun drilling 1.010"

    I haVE made a civil war cannon with a 1" bore. I need to open up the bore to 1.005 to 1.010". The barrel is 36" long. I'm not familiar at all with gun drilling but is a gun drill something i could fabricate and if so how do I sharpen. I have also considered making a reamer then attaching a long shank.
    Thanks, Jim Glass
    So much to learn, so little time

  • #2
    A gun drill is used to do the hole from solid. I'd say that you're after a reamer at this point.

    Depending on what you used for drilling the hole it might already be larger than you think. Twist drills in particular seem to like to cut a touch larger than their nominal size. Did you measure the bore as it is now? I'm just wondering if what with all the chip clearing that it may be closer to the size you want at the bore already. It may be mostly a case of removing any taper towards the chamber end with a reamer.

    This sounds like it would be a nice time for an adjustable reamer too. There's a 1" nominal size that is adjustable from 15/16 to 1 1/16. Just need an extension that way.
    Last edited by BCRider; 05-09-2020, 12:10 PM.
    Chilliwack BC, Canada

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    • #3
      Isn't 0.005 material removal, the region where a hone would be used?

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      • #4
        I think that he means 1.005 to 1.010 final dimension, not from one to the other, though confirmation one way or another would help.

        from what I've read gun drilling uses high pressure through coolant to evacuate chips (peck drilling 36" would be torture). Another option would be to drill out most of it somehow and then use a D-bit for the final dimensions.

        What are you going to be doing the drilling on? Sounds like a 6' lathe would be handy, though I guess you could do it on a smaller lathe by using a series of extensions. Any possibility of starting with some very thick walled tubing with a 1" ID, welding a cap on and turning things to shape from there?

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        • #5
          Seems like he has a 1" bore now, and wants to open it up.

          Reamer will follow the hole, which may not be straight.

          How about a rose reamer, or D-bit, with a full length shank at the final size. Seems like that would tend to maintain straightness, and even straighten a bore that is not straight.

          A gun drill is almost the same thing, if made in solid, without the pressure system. So the D bit or rose reamer and full size shank would do the trick.
          CNC machines only go through the motions

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          • #6
            Do the adjustable reamers have any slight taper to them like hand reamers do? And if not I wonder if it could be jigged up fairly easily between centers in a lathe to allow stoning in a bit of such taper? I'm thinking that this should be doable by using a support in the tool post to produce a 2* taper over about the first 3/8" of the blades if there isn't any now.

            I rather like the sound of the shank being at just a thou or two under the final to aid with guiding the reamer. If possible it would also be nice to bore out the first couple of inches to just a whisker under the desired size so the reamer is guided into line more easily

            Outback, I gather you're after a fit for a patched round ball, right? Have you tried this on a short piece of scrap to find the proper size to get the right sort of fit on the patch?

            Chilliwack BC, Canada

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            • #7
              Thanks for the replies. The barrel is steel tubing I purchased with a .9995 ID and 1 3/8 OD.
              So much to learn, so little time

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              • #8
                I like the "D" bit idea. It should be easy to make your own. It sounds like the hole should be fairly straight. You don't need accuracy for your projectile do you?
                VitŮŽria, Brazil

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                • #9
                  Originally posted by outback View Post
                  Thanks for the replies. The barrel is steel tubing I purchased with a .9995 ID and 1 3/8 OD.
                  With that thin a wall it better be a fancy alloy or you better only be shooting low pressure golf ball loads. That's only 3/16 wall. And a few thou less after you open out the bore. My .50 cal flintlock has a heavier wall on the barrel than that. And as the ID goes up the wall thickness must grow fast to deal with the greater surface area and tensile load in the wall of the tubing around the diameter. Hence why Schedule 80 tube at small ID's has modest wall thickness but larger ID's have wall thickness that grows very quickly. And from the looks of your measurements it appears that you have a piece of Schedule 80 pipe with a max pressure rating of just over 4200 PSI. Pressure from lead or steel balls with more than a minimal charge of black powder will exceed that.

                  Chilliwack BC, Canada

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                  • #10
                    Originally posted by BCRider View Post
                    Do the adjustable reamers have any slight taper to them like hand reamers do? And if not I wonder if it could be jigged up fairly easily between centers in a lathe to allow stoning in a bit of such taper? I'm thinking that this should be doable by using a support in the tool post to produce a 2* taper over about the first 3/8" of the blades if there isn't any now.

                    I rather like the sound of the shank being at just a thou or two under the final to aid with guiding the reamer. If possible it would also be nice to bore out the first couple of inches to just a whisker under the desired size so the reamer is guided into line more easily

                    Outback, I gather you're after a fit for a patched round ball, right? Have you tried this on a short piece of scrap to find the proper size to get the right sort of fit on the patch?
                    Tapered reamers do have a start taper. They tend to chatter for me when running by hand.
                    21" Royersford Excelsior CamelBack Drillpress Restoration
                    1943 Sidney 16x54 Lathe Restoration

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                    • #11
                      3 flute core drill?
                      mark

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                      • #12
                        One could make a lap from 1" aluminum cut down .001 or .002 to fit. Lots of solutions, just pick the best under the circumstances.
                        Last edited by Leadfootin; 05-09-2020, 07:47 PM.

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                        • #13
                          MSC has chucking reamers 1.010" for $200, Made in USA - 1.01" High Speed Steel 8 Flute Chucking Reamer -
                          Straight Flute, Straight Shank, 2-3/4" Flute L
                          I also think your wall thickness is too thin.

                          Steve

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                          • #14
                            D bit or chucking reamer. Weld or silver solder extensions....you'll need a long lathe. Before reaming, set it up and bore the hole as deep as you can, the reamer will be guided by this bore rather than the hole in the material.

                            Agree on the OD being way off....a 36" long cannon barrel thats 1 3/8 OD? 3/16 wall thickness on a cannon?
                            in Toronto Ontario - where are you?

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                            • #15
                              I have been building black powder cannons for 20 years and i would never, ever use a wall that thin.
                              You could injure or kill yourself or some innocent bystander.
                              Seastar
                              I cut it off twice and it's still too short!

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