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Thread: Cannon Barrel Boring

  1. #1
    jeffers is offline Aluminum
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    Default Cannon Barrel Boring

    Hi all,

    I have just started on a project to make a 10 gauge shell black powder cannon like this one:

    http://www.model-engine-plans.com/en...mages/1779.jpg

    It is modeled on a nine pound naval cannon from a drawing I found online.

    I have started turning the barrel to dimension and have a dilemma.

    I am not sure whether the I should bore the barrel before turning the exterior to final dimensions or after.

    At the moment I have the billet in a three jaw chuck and a live centre.

    I plan to do the next phase between centers once a lathe dog I have bought arrives.

    The brass is 2 1/2" in diameter and 14" long.

    If I finish the exterior then I am not sure how to go about holding the piece for boring the centre and if I bore the barrel I will not be able to turn it between centers unless I guess make some bushes to fir the bore and centre drill them.

    What is the best approach?

    What is the best way to protect the work from clamping damage from the lathe dog and also get good contact?

    Any advice would be welcome!

    Here are some pictures of progress so far:

    The 360 brass billet ready for turning



    Ready for turning on my heavy ten with brand new steady rest from Tools4cheap





    Chips starting to fly



    The muzzle almost to final profile and a turning dilemma!


  2. #2
    Joe Michaels is offline Titanium
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    From the photos you posted, it would seem you have made the decision to turn the outer profile of the barrel first.

    My take on things is this:

    1. The bore is critical.
    2. Before you go any further, I would leave the barrel chucked as it is and use a steady rest to support the muzzle end.
    3. I would then drill a pilot hole down the bore and enlarge to final diameter. The bore looks like it is long while fairly small in diameter, so a boring bar might be springy. Can you ream the bore to finished size ?
    4. Once I had the bore finished, I would take the barrel out of the lathe. I'd get a mike reading on the bore at the muzzle (I use telescoping gauges and outside mikes for this)
    5. I would turn a "muzzle plug" out of something like mild steel, turning it to a good close fit in the bore. When I turned the muzzle plug, I'd run a drill down the center of it and tap it. This would let me use a slide
    hammer to get the plug out after the barrel's outer profile was finish turned. I'd open the center hole in the plug with a 60 degree "countersink" so it could also serve as a center to support the muzzle. I might use
    semi-permanent Loctite to make sure the muzzle plug was fixed in the muzzle of the barrel. Heat breaks the bond on the Loctite.
    6. Once the muzzle was plugged, I'd set the barrel back up in the lathe and support the muzzle end on the tailstock center. This would let a lot of the barrel's outer profile be turned.
    7. At some point, you will probably have to turn the barrel end-for-end in the lathe to finish the breech (?) or butt (?) end of the barrel. If you have a good tight fit on the muzzle plug and make it a bit longer, it can serve as a
    "chucking spud" to let you chuck the muzzle end of the barrel w/o damage. The Loctite and a tight fit will probably transmit the torque if you take light cuts.
    8. When you are done turning the barrel's outer profile, you can heat the barrel locally to break the bond of the Loctite (and expand it away from the steel muzzle plug). Screw in a piece of all-thread rod with a piece of bar stock with a hole drilled thru it so it slides on the all-thread. Put a couple of nuts on the free end of the all thread and you have a slide hammer. The slide hammer lets you get the muzzle plug pulled out of the muzzle.

    Joe Michaels

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    jeffers is offline Aluminum
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    Joe,
    Thank you for your reply. You are suggesting what I guess I thought was the solution. There is another obstacle that I am unsure about, I plan to have a removable breech to insert the shell. When I bore the barrel will it need a plug for both ends or is there a better solution for turning between centers after the bore is done?

    The bore tolerance will not be critical as it will be a saluting cannon and will not fire any projectiles.
    The bore will only need to be to close tolerance for the 10 gauge she'll.

    If I make a plug for either end should I make the plug to take a lathe dog or should the lathe dog go on the cannon barrel?

    For a .770 bore would you use a boring bar, drill, d bit or something else?

    Jeffers

  4. #4
    edkolt is offline Hot Rolled
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    Hi Jeffers,

    Why use a shot gun shell. Just ram it up with black powder, like the real one. Make up paper cartridges for loading. That would eliminate making a breech block and firing pin.

    I would drill the bore first to near caliber, then use a boring bar to get a nice looking finish cut; then plug the muzzle end and turn between centers. Make the plug with a shoulder on it to put pressure on the lip of the muzzle.

    What you have started sure looks nice.

    Ed S

  5. #5
    Joe Michaels is offline Titanium
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    I hate to say it, but boring the breech end to chamber a 10 ga shell may not be possible. IMO, you may be past the point of no return since you have turned the profile at the muzzle end. Unless I am missing something, the work sequence to bore the barrel thru and chamber/thread the breech would have been:

    1. Chuck the barrel stock, preferably in a four jaw chuck, face and center the breech end, turn a land for the steady rest to run on.

    2. Support the breech end on the steady rest, then drill through so you create a "tube".

    3. Open with successively larger drills until you are at 3/4" (0.750")

    4. Finish the bore with a boring bar, taking light cuts and making sure to take several "spring cuts" (not in-feeding, but letting the spring or deflection of the boring bar work out). As you close in on the last cut, from your mike readings,
    you will get some idea of how much deflection the boring bar has. On a long bore with a comparatively small diameter, you cannot use a really heavy boring bar, so deflection or "spring" of the bar is an issue. Taking "spring cuts"
    lets the boring bar have less load on it with each pass, even though you do not infeed any more. Working with the "spring" of the bar will let you come to finish diameter. If you go by the micrometer collars on your lathe, the spring of
    bar is actually going to be taking a little less of a cut. This is where you have to take inside mike readings of the bore. The bore is too small for an inside micrometer. I use what are known as "telescoping gauges" and outside mikes.
    Some may say the telescoping gauges are not worth a ---, but I was introduced to them many years ago and it is what I've used ever since on some fine work. I suppose if your cannon were a really precise bore job, you could make
    a plug gauge ahead of time, or, if you had unlimited funds, buy a bore gauge.

    5. Once you get the barrel stock bored, you then can bore the chamber to take the shell, and then cut an internal thread (if that is what you need) for a breech plug (so the cannon's outward appearance is not changed by being made into
    a breech loader). You will need to have enough wall thickness at the breech end to allow you to bore to the root diameter for the internal thread. I would make a boring toolbit with a radius'd end so where the bore for the thread
    ended, there was a radius'd fillet rather than a sharp corner. You do not want a stress riser there. I'd also cut a radius'd "relief" or "undercut" for the runoff of the threading tool.
    Your choice as to breech thread. I am going to say the coarser the better. There will likely not be much length of thread for the breech plug, so the few threads that secure the breech plug will take a heavy shear load when the gun
    is fired. If you look at the threads on breechloading cannon, they were usually quite coarse, and often used a "buttress" thread form for strength. I know this is "only" a saluting cannon, but you are intending to fire 10 Ga shells.
    What kind of peak pressure is developed in the chamber and what the load on the breech plug would be is something you should get some data on and design your breech plug and threads accordingly.

    6. The method described here lets you machine the bore and chamber in one setup, so they are true to each other. Once you have the barrel bored, chambered and threaded, you can then make a plug for each end.

    7.Rechuck the barrel by the breech end, support on the steady rest and turn the muzzle end profile as you are now doing. Turn to some intermediate point where you can stop (such as a shoulder)

    8. Install the plugs at the breech and muzzle end, and reverse the barrel so the breech end is towards the tailstock. Support on centers and finish turning the profile and details on the outside of the barrel.

  6. #6
    Rudd's Avatar
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    1+ for Ed... black powder smells "right". Did the prototype have trunnions, if so, how are you going to handle that? I've always been curious how those were turned on the real thing, some tubes weighing several tons.

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    Joe Michaels is offline Titanium
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    If you look at old cannon barrels, the trunnions were often cast with the barrel. In the old wooden gun carriages, the trunnions were used "as cast", maybe cleaned up by chipping and filing, but not machines.

    On the more precise cannons, I suspect that the barrels were made with enough meat for the trunnions to be fitting into bored holes. Another thought is that the barrels were turned so there was a shoulder some distance ahead (towards the muzzle) of the trunnion centerline. A band or collar might then have been shrunk onto the barrel with the trunnions sticking out of it. The band would bear against the shoulder to transfer the recoil from the barrel thru the trunnions.

    My own suggestion is to start looking at cannons of various ages to get some idea as to how the trunnions were made. Very old cannons, such as Jeffers is duplicating, would have had the trunnions cast with the barrel. As the degree of accuracy and the chamber pressures and recoil all increased, stronger barrels and machined trunnions would have been the logical development.

  8. #8
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    I'm currently finishing my third BP cannon, chambered for 10ga blanks. Although you have the profile done, you can still bore the barrel. Use the first reinforcing band as a land for the steady rest, bore and then thread the muzzle for a screw in moulding plug, these are first used as a point to turn the barrel and second a point for the center to bear on, when the barrel is complete you just cut off the spud, and your done.

    So to bore the muzzle, a boring bar sucks for this, use a gun drill, or core drill, or make a D drill since its brass. I'd suggest that the bore be larger than a .773 bore as the ATF could say you would be making a "destructive device" that could fire "fixtured" ammo, with a bore larger than the than 10 ga that argument goes away, my bores are 1" with a bore in the muzzle moulding of .800.

    The one I've made were breech loading, where I dovetailed a sliding breech block, that contained the firing pin over the shell.

    PM if you need more info

  9. #9
    jeffers is offline Aluminum
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    I can still bore the barrel as it stands. I have plenty of "meat" on the muzzle end for a steady rest. I faced and centre drilled the breech end that is in the chuck.

    Ed, I am making the cannon as a wedding present to a good friend of mine and thought a cannon that fired shells would be safer if not as much fun as lighting a fuse! I have thought about making it dual purpose, i.e. black powder and shell loading, it would have to have a blanking plug of some sort for firing BP.
    I hope to make a brass or steel 10 ga shell to be re-usable and also to alter the charge of BP to make louder or quieter salutes, this will also bring back the aspect of a traditional charging of a cannon.

    Joe, I am going to model the breech on something similar to this by RDG cannons:

    It is a drop in breech block with a screw on ring once the T shaped block is in place. The firing is achieved by hitting the cascabel with a mallet, this is a sprung firing pin which hits the 10 gauge shell cap. I have used one and it works well. I will be able to cut the T with a mill after turning is complete.

    I am not concerned about the trunions, I am going to cross drill and loctite a brass bar in the hole. I will then re-drill/bore the excees in the barrel bore away.

    The drawing I am basing the cannon on is:


    Tom, if you have any pictures of your cannons I would love to see them to see how you did them.

    Jeffers

  10. #10
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    I made two of these cannon with 5" diameter breeches from tough naval bronze. The trunnions were threaded thru with interference fit threads. My bore is 1 3/8" because I have a lot of forged bearing balls that size. It's a muzzle loader.

    I recommend you build your gun from steel if you want a breech loader. I think the brass will soon get battered and things at the breech will loosen up.

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    Rudd's Avatar
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    I've looked at more than a few gun tubes of yore..... Parrots, Columbiads, Rodmans - all civil war period - usually 10" bore, 11 and 15" bores on the rodmans, have integrally cast turned trunnions. A 15" rodman tube comes in at about 50K pounds I'm told. The only thing I can come up with is there must have been a double sided machine like the one I'm using on a loco crankpin in the avatar photo.
    This brings up the question of how do you get the smooth cylindrical (or frustrum of a cone) exterior of the gun tube to continue smoothly past where the trunnions would prevent it from being turned in a lathe. And they are smooth. We had a columbiad at the museum in Key West that was so well preserved you could still see the lathe cutter marks in some areas on the exterior of the tube.
    The Parrott rifle uses a shrunk on reinforce band around the base of the tube - kind of hard to do with a rough casting wouldn't you say?
    Next question, how do you get a 50K pound casting up to the third floor on an island out in the middle of the ocean? Yet, there it sits at Fort Jefferson.

    The Parrott rifle uses a shrunk on reinforce band around the base of the tube - kind of hard to do with a rough casting wouldn't you say? http://www.cityofart.net/bship/parro...charleston.jpg

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    Bruce Nelson is offline Stainless
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    Why do you insist on using a 10 gage shell? I built one of these using the breech loading and firing mechanism copied from the Winchester signal gun. I thought the 10 gage shell problematic, because they are practically impossible to obtain, so I built it chambered for a 12 gage shell instead. Upon test firing this cannon to determine a safe load, I tried various loads until I ended up filling the shell full of black powder with a wad cut from a cardboard shipping box. I buy the powder from Cabela's for about 20 dollars a pound, and I buy the plastic shotgun shells with primers installed for about 20 dollars for 100. The plastic shells can't stand to be reloaded for a second time, so they are expendable. This makes for a loud report and a lot of smoke. I can't see where a 10 gage shell would be an improvement.

    Concerning the trunnion, I am against any compromise of the barrel when attaching the trunnion. I think the best solution would be to machine the trunnions from the oversize barrel stock. So instead of buying a 2 1/2 inch piece of stock, you would probably have to buy a 4 1/2 inch diameter piece of stock. Instead of doing that I threaded the barrel in the location of the trunnions and machined a piece of stainless steel to include the trunnions, the trunnion assembly was bored and threaded to attach to the barrel. It sure is handy to have a cnc machining center for this purpose.

    Lord Byron

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    Ken-Bergen is online now Cast Iron
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    I see no problem with the sliding block design even using brass if only black powder blanks are used.
    However once its out of your hands and if someone uses a factory shell in it I can see it becoming a bomb.

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    jeffers is offline Aluminum
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    Quote Originally Posted by Bruce Nelson View Post
    Why do you insist on using a 10 gage shell? I built one of these using the breech loading and firing mechanism copied from the Winchester signal gun. I thought the 10 gage shell problematic, because they are practically impossible to obtain, so I built it chambered for a 12 gage shell instead. Upon test firing this cannon to determine a safe load, I tried various loads until I ended up filling the shell full of black powder with a wad cut from a cardboard shipping box. I buy the powder from Cabela's for about 20 dollars a pound, and I buy the plastic shotgun shells with primers installed for about 20 dollars for 100. The plastic shells can't stand to be reloaded for a second time, so they are expendable. This makes for a loud report and a lot of smoke. I can't see where a 10 gage shell would be an improvement.

    Concerning the trunnion, I am against any compromise of the barrel when attaching the trunnion. I think the best solution would be to machine the trunnions from the oversize barrel stock. So instead of buying a 2 1/2 inch piece of stock, you would probably have to buy a 4 1/2 inch diameter piece of stock. Instead of doing that I threaded the barrel in the location of the trunnions and machined a piece of stainless steel to include the trunnions, the trunnion assembly was bored and threaded to attach to the barrel. It sure is handy to have a cnc machining center for this purpose.

    Lord Byron
    My preference for a 10 gauge she'll is for safety. They are readily available in New England or by mail order.
    The shells are loaded with the correct charge for safety and effect.
    I am making the cannon as a wedding present so ease of use is also important.

  15. #15
    packrat2's Avatar
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    Brass 10 ga. shells can be found,{gun shows & on line} brass shells can be reloaded lots of times with black powder, also
    12 ga. brass shells are available..

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    jeffers is offline Aluminum
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    Decided to follow Joe's advice and bore the barrel next. It was a bit of a challenge as I do not have a drill for 10 gauge diameter or one long enough. Ordered one off e bay and started drilling while I was waiting:

    Ordered a steady rest from Tools for Cheap. It seems to work well.
    3/4" x 18" contractor intallation drill arrived and I managed to get a hole through. Brass is really challenging to drill as it grabs the drill bit and pulls the chuck out of the tail stock taper. I used the boring bar holder on the drill bit to support and prevent the chuck from being pulled out, this helped a lot. It was difficult to clear chips though because the flutes only helped for the first few inches, after that the whole drill bit had to be withdrawn which meant taking the tailstock off evry half inch of progress or so. These are the drill bits I used:

    I then moved on to a home made boring bar out of 3/4" steel. It gave a lot of chatter as I exceeded recommended length for boring of three to one. I decided it would not be critical for this barrel as it was only going to fire blanks.

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    jeffers is offline Aluminum
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    Got the barrel bored and then I turned some inserts to fit the barrel at either end to be able to mount between centres to finish turning the outside detail:

  18. #18
    edkolt is offline Hot Rolled
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    Looking good. You made a lot of progress.

    I like the looks of the steady rest also.

    What's next?

    Ed S

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    Nice job so far.

    I'm curious to see how you go about getting the trunnions on the barrel. (Something I've always wondered about.)

    -Ron

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    TDegenhart is offline Stainless
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    To control the grabbing of brass, blunt the edge of the drills to give a zero to negative rake of the cutting edge.

    Tom
    SteveM and rdhem2 like this.

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