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  • Spinning Copper Cones

    I got a new project I need about 50 copper cones that are about 8” tall and 4” wide at the bottom. I tried to farm this out to a spinning shop in Dallas but was told that they didn’t think it was possible with the small radius of the tip 1/4” I was asking for 20ga type 110 copper. Is there another way to do make this? They also did Hydro forming and deep drawing. But this would need high dollar molds for such a small parts run.

  • #2
    Must the cones be seamless, is the taper straight, is a hole permitted at the apex. Par
    I never trust a fighting man who doesn't smoke or drink.
    William Halsey

    As a Machinist & Gunsmith I like to hear how to not can't do. P.A.R.

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    • #3
      Seamless would be correct or at least just a butt weld maybe tiged. Small hole at top would be fixable.

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      • #4
        Try a sheet metal shop and like you say TIG welded seam and hole at end
        Glen
        Been there, probably broke it, doing that!
        I am not a lawyer, and never played one on TV!
        All the usual and standard disclaimers apply. Do not try this at home, use only as directed, No warranties express or implied, for the intended use or the suggested uses, Wear safety glasses, closed course, professionals only

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        • #5
          I contacted another spinning shop on their website they had an aluminum cone that was 10” tall and about 27deg. I need 21.25deg maybe they can do it. I have never had spinning done how much you think I’m looking at to have this done?

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          • #6
            Jeremy, if I had to guess, you want some Monroe-effect cones. First, the gauge you get SPUN is less than the gauge you start with due to the metal stretching a bit.
            Second, if I guessed right, why not just have them rolled up by a tin-whacker. As long as the seam butts, a bead of solder would hold until you are finished, and silphos, if you want continuity. He may have to scratch his head to calculate the angle, but it IS sheet metal 1011
            Duffy, Gatineau, Quebec

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            • #7
              Yes Duffy you are correct. We or the people that want us to make the shape charge want to go after some 16” navel rounds. They want a 2” to 3” diameter hole and at least threw 4” steel. We may be bumping the cone base to 6” if need be. Witch is going to take about 7 pounds of pop mix to do the job. (That’s going to be loud!!) I could have the flats CNC laser cut locally. But I don’t think the local sheet metal shop is up to the task of rolling them.

              Ok time to go dove hunting, be back later to night.

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              • #8
                Jeremy, a long time ago, I made up the charge, (C3-it was THAT long ago!) and blew a 16" navel shell at the old Eglin training ceter. IIRC, it was an AP round with only a 40 lb explosive content. The walls were MUCH thicker than 4". Again, from memory, the GP round had an NEC of over a hundred pounds, and thinner walls. I seem to recall that the AP rounds were filled with ammonium picrate, while the GP rounds were TNT. In any case, the shaped charge form that we used was about the size of a tomato can, (28 oz,) with three wire legs spot welded. The legs were notched every inch for ease of shortening. I THINK the can had a copper cone, and I THINK I set the stand-off at 4". It worked, by the way.
                Duffy, Gatineau, Quebec

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                • #9
                  Duffy I know exactly with shape charge you’re talking about. We have a few. This project is going to an island that was a bombing range. So they want binary explosives and there are close to 50 projos to shoot. Most have just the lifting lug for a fuse. And they have No clue as to what is in them. So if the projo dos not detonate they want to be able to see in side. That’s why they want a 2” to 3” hole.


                  I have a picture some ware of your shape charge.

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                  • #10
                    How about electroplating to build up the cone?

                    I was looking at some waveguides made up that way today.
                    Paul Compton
                    www.morini-mania.co.uk
                    http://www.youtube.com/user/EVguru

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                    • #11
                      Jeremy, There is a bit of confusion here, but here is MY take on your info. First, the shells ARE NOT AP. AP have NO lifting lug. They have a staked on penetrative cap of hardened steel, directly to the projectile. This was followed by a streamlining wind shield which contained a great wad of flourescein dye to mark fall of shot in the sea. There was ONLY a base fuze.
                      These MUST be GP shells to have a frontal fuze pocket. It was evidently cleverly designed with a thread that could withstand the hoisting weight of a screw-in lug. That being the case, the fuse pocket will be a thin sheet metal lining, probably copper or brass.
                      To confirm all this, an AP round weighed about 2800 lbs, while a GP round weighed in at about 1900 lbs.
                      I assume that these are not fired projectiles, (or else SOMEONE forgot to remove the lug and install a fuze!) That being the case, if one could be hoisted up and buried up to its fuse line, then the lug removed REMOTELY, (by the way, do you have a handy-dandy rocket wrench?) Then, if it did not blow, have a peek inside the pocket. assuming things are in good shape, fill with water, rig a cordless hole saw to trepane the pocket and test what is inside, (TNT is my bet.)
                      Historically, Lyddite, (ammonium picrate,) was the least shock-sensitive explosive and was pretty well essential for big AP shells. The downside was that it required a serious booster on the fuze. TNT was the next "least sensitive" explosive, and things generally went downhill from there.
                      All of this would not be NEARLY as much fun as a shaped charge, but might yield a lot more info quickly. Finally, if I am correct, then it would be a sraightforward process to rig a rack to hold a projectile and steam the TNT out through the fuze pocket. That way the scrap is handier to collect! (AND you could sell the empties for GATE POSTS!
                      Duffy, Gatineau, Quebec

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                      • #12
                        Jeremy,

                        Caution: The following is pure speculation and reasoning on my part, and not based on any actual experience.

                        You are in a unique position to experiment with fire-forming, a more exciting form of hydroforming. You would sandwich a plate of annealed copper between one slab of steel with a small pocket for an explosive charge, and another heavy duty piece with the desired shape machined into it. Bolted together with the biggest, most numerous bolts. Set off the charge, observing all your usual safety precautions. The copper will attempt to comform to the shape of the cavity - or rupture. You might have to do the job in stages with successive small charges and annealing the copper between shots. The process may be laborious, but it seems like it would be comparable to metal spinning, and you might do it yourself.
                        Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                        ~Practitioner of the Electromechanical Arts~

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                        • #13
                          I am new here but this was a FASCINATING discussion!!! Do I understand correctly that there are some 16" naval shells someplace that need to be "made safe" and there are going to be explosively "opened" in order to either blow them up or to see inside to be sure they are safe?

                          This needs to be a segment on "dirty jobs" I want to see video of it!!!

                          This would be awesome to see.

                          John

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                          • #14
                            Duffy you’re in the ball park. These are fired rounds. And from my understanding it was not unheard of to use a GP round for a dummy. Just leave the lug in place. Or these are AP rounds and the wind screen has been torn off and mangled. I’m working on what they tell me. Matt is going to the tropical island the end of this month and see firsthand. (I sure hope he gets freeze brain from the margaritas at the hotel) And these have been sitting in the salt spray and salty sand on the beach. For probably close to 50 years.For some reason they don’t like to move fired shells too much. And a forklift would probably get stuck.

                            Yes hemmjo- People do get paid to blow stuff up all day long. It’s far easier to blow a round up if it didn’t go off. It’s already in a safe place. It was going to blow up when it hit anyway. Explosives are cheap compared to time and people.If they don’t blow up then you can confirm that there is concrete in the round. Even some rounds might be filed with concrete but still have the high explosive booster in it.

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                            • #15
                              Duffy - Is this the tomato can? http://bbs.homeshopmachinist.net/showthread.php?t=38813

                              Hemmjo- Video at bottom of last pic. http://bbs.homeshopmachinist.net/showthread.php?t=46597

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