The 24-Pounder Naval Gun model I am building is approximately 1.8 inches in diameter and about 9.5 inches in total length. The barrel tapers along the entire length at 3.8 degrees, and interrupted by six bands. These bands originally added to add some much needed strength to the gun, however, in my model they are mainly decorative in function.
I started with a piece of cold rolled steel purchased from a local supplier. The round bar originally measured 2.5 inches in diameter and intended for another project. I opted to use this material for the 24-pounder almost on a whim, and it took quite some time to remove the extra mass. As a general rule, being a hobbyist, I do not worry about running my lathe hard or for optimal efficiency. I do not have hard deadlines or unites per hour to contend with. Currently, the motor on my South Bend underpowered. There is no reason for me to push my machinery and tooling to hard.
First, once the steel is between the centers of the old south bend, I removed a lot of material to bring the diameter down to 1.9 inches. This dimension would give me some extra wiggle room in the event of an “Opps”. Then, starting with the muzzle, I took measurements off of the blue prints. Next, I transposed the dimensions to the material on the lathe using layout fluid and my calipers.
Defining the Barrel Bands
Once each measurement is marked in the layout fluid, I used the tool post to scribe a line around the material. Then, I put the lathe into gear and made light cuts to define the various bands starting from the muzzle. During this time, I noticed an issue. The blueprints I had consisted of the the pages. When I taped the three pages together, I made a mistake and added in some extra length from the overlap of the three pages. This caused me to create nine of these bands lines. After some head scratching, I sorted everything out and simply removed the extras from the breech end of the muzzle.