Making a custom mold advise needed
I have half of this figured out. My idea is for a simple to produce mold for testing different shapes and weights of pellet. My tools are limited to mostly hand tools however a surprising lot can be accomplished given time, trial and error, and lots of stopping for measurements. I’m not making them by the hundred for target practice or anything. My plan is to trial and error my way through different concepts and hone craftsmanship in the process.
I can polish the sides of two pieces of aluminum bar stock to near mirror and grind the top flat so they match seamlessly. Instead of hinging the mold I will hold the two halves together with pins and clamps. I could drill it out easily enough and counter sinking it will make a simple conical skirt. I won’t attempt hollowing the skirt at first and could try gas checks or maybe paper patch. Where I am stuck is creating the head and gas checks. For the head of the pellet I have considered putting a metal sleeve down into the mold to protect it with the bit chucked into a Dremel suspended in a crummy drill press like device. Then rotate the entire mold along the bench as the burr head cuts and use the sleeve as a sort of fence to limit it’s cutting depth. Measure, adjust, replace with different size sleeve, repeat until desired result. A modified wire nail could be used similarly to cut gas checks into aluminum. I would be glad to hear any improvements to this.
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Pab,
I’m not having a random issue, really…. I thought bananarama entered the H2 conversation stupidly and I reacted, perhaps a little too harshly but a guy with a very low post count who enters a thread and sets it back, adding no value whatsoever annoys me.
Almost simultaneously, he tells us he has it half figured out regarding making a mold when he clearly has no freaking clue where halfway is. I don’t mind questions at a novice level but I do have a problem with a novice getting into a debate with an expert and at least not taking the time to figure out who he’s talking to. Bman might have been upset by the quick dismissal of his idea but he might also have noticed who it was coming from instead of adding his little rant dismissing Walter as a troll and blabbering on.
Yeah, I need sensitivity training but when some guy with two sharp rocks says he’s working on cold fusion starts yapping about the guys saying he has the wrong tools….
Brilliant post as always bud, informative, clear and from lots of experience. I now am starting to get a clear idea of this ‘cherry’ business!
Dunno whats up with Jerry. Usually the first in to give as much help and advice as possible. Guess he’s taken a dislike to the Banana Man! 😆
Nothing wrong with Jerry, Pabs.
Banananananana ramma is a ……….. oops my inside voice sneaking out again……..
😆 😆
Brilliant post as always bud, informative, clear and from lots of experience. I now am starting to get a clear idea of this ‘cherry’ business!
Dunno whats up with Jerry. Usually the first in to give as much help and advice as possible. Guess he’s taken a dislike to the Banana Man! 😆
Nothing wrong with Jerry, Pabs.
Banananananana ramma is a ……….. oops my inside voice sneaking out again……..
Hey up Walt’ 😀
Brilliant post as always bud, informative, clear and from lots of experience. I now am starting to get a clear idea of this ‘cherry’ business!
Dunno whats up with Jerry. Usually the first in to give as much help and advice as possible. Guess he’s taken a dislike to the Banana Man! 😆
Ban, there is a place for pure craftsmanship unaided by mechanical means and this aint one of em. Sorry I have to disagree with ya.
Custom mold making requires a high degree of precision. Although high precision is possible with hand tools, such projects are usually in the area of outside forming, where you can sand, or hand file, then look or measure your results and approach it slowly. given enough time, art, and patience, a good craftsman can get very good results.
the problem with molds is twofold. the first is that it requires exact internal machining (which means you cannot ‘see’ your results and usually the cavity is too small to actually get in there and measure) and that means at a minimum, repeatability; and index or registration of an exacting nature, i.e., the ability to locate the cutting bit with respect to the cavity very precisely.
Which means, you cannot use a hand drill, this must be done on a lathe or mill. Normally for one off projects like yours the cherry, which is the cutting bit shaped on one side like the profile of your bullet, is cut from a piece of tool steel for an iron blank, but that would only be for production; for DIY I would highly recommend using aluminum mold blanks, they are much easier to cut and will still produce thousands of good bullets. With larger bullets (.45) the cherry is fat, so very strong and stiff. but the smaller the bullet, the smaller the diameter of the cherry, so the tool flexes more and you have precision problems. therefore .22 is one of the hardest to do because your tooling will have to be very small. Longer bullets require longer cherries, again compounding the flex problem. Holes like this are nearly impossible to measure because they are so small, and because bullets usually have ridges in them to seal gases which means it isn’t a smooth cylinder you are measuring, it has rings that bulge out and grooves that go into the wall… most casters will cut the mold, drop a dozen bullets from it then measure the bullets to get an idea of the accuracy of their mold. That’s why registration, or index, is important, so you can put the mold back into the machine and re-cut half a thousandth from the center ring if you have to, after having cast a few bullets and measuring them.
good luck on your project.
aloha,
walt
(no, not that walt. yes there are 2 of us here but I’m also grumpy sometimes. hey pab)
Psssst….He can’t see your posts
😆 You know he’s toggling just to check.
Besides, I really am fascinated… if I wasn’t blocked, I might even pass along where tofind the easiest to use online calculator and some observations about variables he’s not considering.
so 70 foot pounds it is. At 70fpe the heaviest projectile I can expect to fire around 950fps is
74.282 x 450240 / 950 x 950 = 37.06
so I should keep the weight below around 35gr.
… after fumbling over finding the square root and recalculating it all after I realized I grabbed the weight on the wrong tin of pellets:banghead: I ended up with these numbers. Anybody good in math or that has time to kill please check my work.
If you aren’t good in math you can kill time with this old flash game where you can play with kitties as it seems we have a lot of people here who are… entertained by cats.
Edit: Yeah it helps if there’s a link http://www.addictinggames.com/kittencannon.html
————————
Now to check out that Greenhill equation. While this is not actually Greenhill’s equation, it is a modified version by Les Bowman T = 3.5 * V^0.5 * D^2 / L
I’m not entirely certain I should even bother calculating this because it is designed for bullets. Two bullets of the same weight could be radically different length if say one is a literal cone and the other is a cylinder. I guess later I’ll solve that equation to figure out roughly the length I shouldn’t exceed but as long as I keep it below what has previously worked I should be ok, no? I guess I’ll pick the conservative shape that JSB did with the Exact Jumbo Monsters I have and go with a cylinder. The shape of the head by eye looked to be a perfect half sphere so I measured. The distance (along the axis) from the point to where the side of the pellet rubs the barrel is one radius so yes that’s pretty much a perfect half sphere.
I have a lot of work to do tonight so a little math is all I’ll bring for now.
Nice I got over 1300 feet.
At any rate, why are you setting 70 fpe as a max?
Why not just go a little higher and just get a 40 grain .223 mold, and size them back to .22?
so 70 foot pounds it is. At 70fpe the heaviest projectile I can expect to fire around 950fps is
74.282 x 450240 / 950 x 950 = 37.06
so I should keep the weight below around 35gr.
… after fumbling over finding the square root and recalculating it all after I realized I grabbed the weight on the wrong tin of pellets:banghead: I ended up with these numbers. Anybody good in math or that has time to kill please check my work.
If you aren’t good in math you can kill time with this old flash game where you can play with kitties as it seems we have a lot of people here who are… entertained by cats.
Edit: Yeah it helps if there’s a link http://www.addictinggames.com/kittencannon.html
————————
Now to check out that Greenhill equation. While this is not actually Greenhill’s equation, it is a modified version by Les Bowman T = 3.5 * V^0.5 * D^2 / L
I’m not entirely certain I should even bother calculating this because it is designed for bullets. Two bullets of the same weight could be radically different length if say one is a literal cone and the other is a cylinder. I guess later I’ll solve that equation to figure out roughly the length I shouldn’t exceed but as long as I keep it below what has previously worked I should be ok, no? I guess I’ll pick the conservative shape that JSB did with the Exact Jumbo Monsters I have and go with a cylinder. The shape of the head by eye looked to be a perfect half sphere so I measured. The distance (along the axis) from the point to where the side of the pellet rubs the barrel is one radius so yes that’s pretty much a perfect half sphere.
I have a lot of work to do tonight so a little math is all I’ll bring for now.
Interesting stuff ban’ 😀
Psssst….He can’t see your posts
Fascinating
Instead of waiting to drive out to the everglades I just decided to fire a few shots in my apartment at full power a little while ago. I probably should have tried full power some other time I was at my everglades “proving grounds”. Windows shook, car alarms went off, the neighbors baby was crying 🙄 and I got an average of 1016 with my stock condor .22 24″ 3000psi which comes out to 32.4 x 1016 x 1016 / 450240 = 74.282
so 70 foot pounds it is. At 70fpe the heaviest projectile I can expect to fire around 950fps is
74.282 x 450240 / 950 x 950 = 37.06
so I should keep the weight below around 35gr.
… after fumbling over finding the square root and recalculating it all after I realized I grabbed the weight on the wrong tin of pellets:banghead: I ended up with these numbers. Anybody good in math or that has time to kill please check my work.
If you aren’t good in math you can kill time with this old flash game where you can play with kitties as it seems we have a lot of people here who are… entertained by cats.
Edit: Yeah it helps if there’s a link http://www.addictinggames.com/kittencannon.html
————————
Now to check out that Greenhill equation. While this is not actually Greenhill’s equation, it is a modified version by Les Bowman T = 3.5 * V^0.5 * D^2 / L
I’m not entirely certain I should even bother calculating this because it is designed for bullets. Two bullets of the same weight could be radically different length if say one is a literal cone and the other is a cylinder. I guess later I’ll solve that equation to figure out roughly the length I shouldn’t exceed but as long as I keep it below what has previously worked I should be ok, no? I guess I’ll pick the conservative shape that JSB did with the Exact Jumbo Monsters I have and go with a cylinder. The shape of the head by eye looked to be a perfect half sphere so I measured. The distance (along the axis) from the point to where the side of the pellet rubs the barrel is one radius so yes that’s pretty much a perfect half sphere.
I have a lot of work to do tonight so a little math is all I’ll bring for now.
Jerry,
No I have killed hundreds of cats, I just missed one 50 cats ago.
Roachcreek
Now don’t go scaring them with those horrible kitties.
here guys , something to do while we talk about guns.
http://www.richsalter.btinternet.co.uk/
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I’m not having a random issue, really…. I thought bananarama entered the H2 conversation stupidly and I reacted, perhaps a little too harshly but a guy with a very low post count who enters a thread and sets it back, adding no value whatsoever annoys me.
Almost simultaneously, he tells us he has it half figured out regarding making a mold when he clearly has no freaking clue where halfway is. I don’t mind questions at a novice level but I do have a problem with a novice getting into a debate with an expert and at least not taking the time to figure out who he’s talking to. Bman might have been upset by the quick dismissal of his idea but he might also have noticed who it was coming from instead of adding his little rant dismissing Walter as a troll and blabbering on.
Yeah, I need sensitivity training but when some guy with two sharp rocks says he’s working on cold fusion starts yapping about the guys saying he has the wrong tools….
OOooh, talking about cold fusion, have you seen the stuff about the Italian guys who claim they have one working, indeed for the past two years??!! Had some independent scientists looking at it now and they have confirmed it has about 400w going in, and about 15000w coming out! Not sure its ‘actual’ cold fusion,but something is going on in there… Nickel and hydrogen as the fuel, minimal lead shielding, zero radioactive waste, no gamma rays being emitted! Gotta be a hoax?
http://pesn.com/2011/01/27/9501752_Italian_cold_fusion_saga_continues_with_new_papers_released/