Ball mold - a nice looking failure

[Canute Rex]

A friend of mine just built a rifle using a Coleraine 50 caliber barrel - or so he thought. Turned out to be a ~49 caliber barrel. He emailed and asked me if I had a .485 or .480 mold. Of course I didn't. There's a man named Tanner in England who will make you any size mold ((no title)) out of brass, but I decided to give it a whirl. I ordered a 31/64" (0.484) ball end mill and fired up the lathe. Made a couple of brass hockey pucks with a rim/cutout that fit together and did a .242 plunge cut in each. Milled off flats on the edge and drilled and countersunk for a sprue hole. Milled a couple of slots in the sides for handles and drilled/tapped for 8-32 screws.

After I took the photos I chamfered the corners and honed the surface of the protruding side with a diamond sharpening hone.

Aaaannnd the ball end mill must have wandered by .005" because it was .485 pole to pole, but .495 around the equator. I'm going to try again with a smaller cutter. Pretty, though, if I may say so myself. And I used both my machine tools! Shop time is never wasted time.

 

[JHB]

Nice work. Lee makes a .480 mold.

 

[Canute Rex]

Thanks, JHB. If my second attempt has an equal lack of success I'll refer my friend to Lee.

 

[Flintlock]

Just call Larry Calahan and he could make you a small bag mold.

 

[The Crisco Kid]

Maybe that's why the old timers filed out a round cherry. It would be very interesting to shoot a few of those out of round balls just to see how they do. They look a lot better from here than the balls I cast out of those molds that Dixie Gunworks used to sell.

 

[Brokennock]

A friend of mine just built a rifle using a Coleraine 50 caliber barrel - or so he thought. Turned out to be a ~49 caliber barrel. He emailed and asked me if I had a .485 or .480 mold. Of course I didn't. There's a man named Tanner in England who will make you any size mold ((no title)) out of brass, but I decided to give it a whirl. I ordered a 31/64" (0.484) ball end mill and fired up the lathe. Made a couple of brass hockey pucks with a rim/cutout that fit together and did a .242 plunge cut in each. Milled off flats on the edge and drilled and countersunk for a sprue hole. Milled a couple of slots in the sides for handles and drilled/tapped for 8-32 screws.

After I took the photos I chamfered the corners and honed the surface of the protruding side with a diamond sharpening hone.

Aaaannnd the ball end mill must have wandered by .005" because it was .485 pole to pole, but .495 around the equator. I'm going to try again with a smaller cutter. Pretty, though, if I may say so myself. And I used both my machine tools! Shop time is never wasted time.

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"...Nice looking failure"

I disagree. It is nice looking. But failure?
Did you learn something in the process?
Do the cuts and slots and such you made for the mold handles fit properly? Do the two halves close properly?
If the answer to any one of those questions is, yes, I would deem it a success. Any 2 or more, a great success.

 

[Canute Rex]

"...Nice looking failure"

I disagree. It is nice looking. But failure?
Did you learn something in the process?
Do the cuts and slots and such you made for the mold handles fit properly? Do the two halves close properly?
If the answer to any one of those questions is, yes, I would deem it a success. Any 2 or more, a great success.

Thanks, Brokennock. I cast a dozen balls and left them with my friend. He's going to try them out. If they shoot straight I'll cast him some more.

I'm actually quite pleased with the fit and functionality of the piece. When I first fitted the halves together (before the sprue hole) I could feel the air pressure and then the suction when I pulled them apart. I'm going to try a different technique for centering the ball end cutter and see how close to the cutter diameter I can get. It's a good winter project.

 

[Cheyenne River breaks]

Rex,
If you try it again with that same cutter, make sure your tailstock is on the same axis as the headstock. It would even pay to put the cutter in the tailstock chuck then use an indicator clamped in the headstock chuck to make sure it is on center. And last but not least, orient your cutter (if it is two flute) with the flutes on the sides, not top and bottom. Many lathes have just enough wear on the bottom of the tailstock that it will be low which could cause an overbore situation.
My 2 cents, for what it's worth.
Brett

 

[Canute Rex]

Rex,
If you try it again with that same cutter, make sure your tailstock is on the same axis as the headstock. It would even pay to put the cutter in the tailstock chuck then use an indicator clamped in the headstock chuck to make sure it is on center. And last but not least, orient your cutter (if it is two flute) with the flutes on the sides, not top and bottom. Many lathes have just enough wear on the bottom of the tailstock that it will be low which could cause an overbore situation.
My 2 cents, for what it's worth.
Brett

Good advice, Cheyenne. I think my tailstock needs a rebuild just to tighten it up in general. I don't think it's off center, I think it's a couple of thousandths loose.

 

[Bushfire]

I guess you can polish a turd, even if that didn't turn out it still looks quite nice!

 

[Tyler L]

Good advice, Cheyenne. I think my tailstock needs a rebuild just to tighten it up in general. I don't think it's off center, I think it's a couple of thousandths loose.

That's a good looking mold for a first attempt; better than I could do!

I just happened to use a ball endmill in my lathe today and I had the same issue: the worn tailstock couldn't hold it rigidly enough. Technically, we shouldn't be holding endmills in the tailstock anyway, but we do what we have to!

Another way to try would be to hold the endmill in the toolholder somehow and line it up on center. A lot of machinists like to do that with drill bits so they can drill with the carriage.

What about this?: Use your mill to cut the pockets and then chuck each half in the lathe, indicate off the pockets, and then turn the shoulders. Or you could cut the shoulders in situ in the mill with a boring head. Just a thought.

 

[Canute Rex]

Hey Tyler,

I started by using the tailstock and then switched to the tool holder. Tried my best to center it, but my best wasn't good enough. I have some ideas, though.

Tip for others crazy enough to try this: I needed to do a 0.242" plunge, but was getting some chatter. I did a powered plunge to about 0.230" and then turned off the lathe, loosened the drive belt, and cut the last few thousandths rotating by hand.