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Boring tapered hole

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  • Boring tapered hole

    How best to bore a tapered hole in steel?
    Trying to match the taper of a civil war cartridge (Burnside) in the breech block.
    Lathe plus boring bar or ...?

  • #2
    I think you have it, lathe and boring bar with compound set at the proper angle.

    THANX RICH
    People say I'm getting crankier as I get older. That's not it. I just find I enjoy annoying people a lot more now. Especially younger people!!!

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    • #3
      You could set up in the lathe with a 4 jaw chuck or a faceplate with an angle block. To bore with boring bar, you could set the compound slide to the angle or use a taper attachment. On the mill, you could hold the breech block in the mill vise and use a Tree boring head set on the desired taper.

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      • #4
        Lathe sounds like a good possibility.
        Another thought would a d reamer after step drilling out most of the waste before reaming.(?)

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        • #5
          Tell yourself how important it is that the hole is bored straight. It will come out tapered. Happens to me every time.

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          • #6
            Suspend a perfect case between centers. Put a dial indicator on your compound so its dead center for height on the case. Adjust until as perfect as you can get it. Remove case. I've done tool tapers this way, and they are less forgiving than cartridge cases. Do you know how much under size the case is supposed to be to the chamber? I'd suggest small carbide boring bar.
            *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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            • #7
              At the risk of arousing wrath, can I suggest a CNC lathe is perfect for this?
              I machine small taper locks this way for pulleys.The Fenner ones are far too big.
              This is actually the drive for the Z-axis on my CNC Mill.
              Cheers
              Roger
              Taper Locks in toothed pulleys

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              • #8
                Originally posted by Bob La Londe View Post
                Suspend a perfect case between centers. Put a dial indicator on your compound so its dead center for height on the case. Adjust until as perfect as you can get it. Remove case. I've done tool tapers this way, and they are less forgiving than cartridge cases. Do you know how much under size the case is supposed to be to the chamber? I'd suggest small carbide boring bar.
                Still need to take some measurements of the case vs the drawing of the chamber but this sounds like a good way to go.
                will probably do an initial run at it in machinable wax or aluminum so as to get the feel for it before attempting the real material.

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                • #9
                  Why not machine a male one first , this will be easier to measure and you can get the exact settings for the top slide or taper turning attachment, the component produced could then also be used as a gauge for the actual chamber
                  John
                  Knowledge withheld is knowledge lost

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                  • #10
                    I actually have the cartridge cases that are for the gun. Measurements off those would be the way to go plus a small allowance for case expansion on firing.

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                    • #11
                      Making a custom chambering reamer with the dimensions taken from the cartridge cases is probably going to get you the closest fit. At least that approach has been working for me. Make a replica of the round on the lathe, mill flutes into the replica ( I prefer hex stock as it comes in handy for indexing the flutes), harden, sharpen and you are good to go. By all means you can use a boring bar and taper set at the compound to remove most of the metal.....then finish up with the custom reamer to rectify any errors introduced by flexing or other factors.

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                      • #12
                        Originally posted by markx View Post
                        Making a custom chambering reamer with the dimensions taken from the cartridge cases is probably going to get you the closest fit. At least that approach has been working for me. Make a replica of the round on the lathe, mill flutes into the replica ( I prefer hex stock as it comes in handy for indexing the flutes), harden, sharpen and you are good to go. By all means you can use a boring bar and taper set at the compound to remove most of the metal.....then finish up with the custom reamer to rectify any errors introduced by flexing or other factors.
                        Making a D reamer (D-bit) will be a lot quicker than making a fluted reamer.

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                        • #13
                          I think the d bit would be the way to go. I have a drawing of one that Brian Rupnow designed that looks adaptable.
                          Also mulling the idea of casting the breech block in silicon bronze as well as the lever components.
                          Not exactly authentic, but I'm only going for a replica shooter anyway.
                          I think casting these parts and finishing them would be simpler than machining entirely from bar stock.
                          ​​

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