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.
All Replies
I’m no machinist but I have had the privilege of watching several molds made by a guy who has made a bunch of them (well over 100) and can crank one out in a few hours from making the cherry to mounting the mold in hand made handles. That includes the .25 molds we’ve used for years now and the .22 mold for the near dead .22 project. (BTW, I still think those .22s will shoot but I don’t think they can handle a choked barrel… sadly, that was the point, work from a choked barrel like the .25s!)
Having watched the process and asked questions, I’ve learned a few things about cherries, materials and the whole process. There are a bunch of variables and a bunch of ways that near perfect machining can turn to crap! A guy that has done the work for years is a good source to learn all the mistakes and lessons learned from.
I’ve also had custom molds made by commercial firms. The ones I dealt with have some strict guilnes for design and at the time I was dealing with them, would not even consider making a .22 mold. I suspect the flex in the cherry was the biggest issue. Even for my boat tailed .32, the company had a minimum size for the base (or any other part of the cherry). The issue is flex, even with a zero run out tool, when cutting, the cherry will flex and the company can’t spend an inordinate amount of time on a tiny mold and make any money.
The most important part of making a mold is process, followed closely by precision execution of that process. That means learning what to do and then getting the proper tools and skills to use them. It is silly to think one can design a decent pellet (while ignoring all actual results, experience in favor of a couple formulas) and then use a drill in a frame and a simple vise to make them.
I’ve got a whole basement shop full of tools I know how to use and more in the garage (I’ll wager it’s a better set-up than what you’ll find in most apartments…) and I won’t try making a mold (even as I’m marketing the kid’s slug sales). That’s because I KNOW (from other’s experience) that to make molds requires some precision tools and jigs that I don’t have (and can’t use without a lot of practice/learning).
If anyone wonders why I’ve been harsh on this thread, it’s not just because of the H2 thread or that someone is in over their head. It’s because of an arrogant attitude and dismissal of others experiences. Experience is what you get right after you need it. Learning from someone else’s experience is a lot smarter than what we’ve seen here.
Didn’t have time to check that website out, I’m in the middle of designing something else that’s using up most of my 3 or 4 brain cells right now. but gauging from that picture, that guy’s using cnc machining, which i know nothing of. for sure the bit on the left is for cnc as it has a spiral flute, like a normal twist drill, and the excerpt mentions interpolation of circles; so he’s sticking the cherry on the left into the hole and then having the machine move it in a tiny circle so that all the sides of the cutter are used in turn. but from what i can see, this cutting is very flexy and won’t yield a true cut unless you are taking very, very small bits over multiple passes in soft material. but for normal mortals like myself who have manual machines, the cutter on the right is what i was describing earlier. it has only 1 cutting surface, that longitudinal pie cutout on the left; you stick the cherry into the hole and then advance it toward you, away from the hole axis, and let the left edge cut the bullet profile for you. It’s done in 1 pass and because there is more metal in the cherry due to only the 1 piecut, it is much stiffer than the cutter on the left.
walt
lots of good stuff on that page, i never have looked into making molds, i have only bought them. I would rather spend my time casting than making molds.
I enjoy casting but i enjoy shooting more than casting, so on handgun calibers that see allot of lead down range i have 2 – 4 cavity molds working when casting.
I have been casting since the 80′ s , i have allot of fun doing stuff like that , but the dam computer keeps allot of stuff from happening like that, when i used to come home from work in bad weather and go to the garage and cast or reload , most of the time i am sitting in front of the computer. 👿
I cut out a steel blank yesterday to start on a mold, but spent the rest of the day getting stuff done around the house in the nice wheather.
My idea is to clamp two pieces together and idex drill them,then drill an undersize hole for my cavity, then turn down a drill bit to drill the hole size to a land riding body for the pellet. then cut down a drill bit to only cut the leading edge of the pellet to bite into the lands , maybe .215 ,, with a .212 body. the just chamfer the base to have a .221 or so bore filling tail on the pellet.
This is a way to get a mold and make a pellet with the stuff i have available. dont know if it will work but i will see. 😆
Walt in Hawaii and Voltar, sorry I didn’t see your posts. They must have come in while I was typing. I’m guessing Voltar is the Not in Hawaii Walt. (portmanteaux of Volta+walter by chance?) Anyway, Walt in Hawaii I think if the method you just mentioned and my original post had a baby it would end up as the following.
“To reduce the strain on the cherry the cavity are drilled almost to final depth with a drill as large as possible. Then the cavity is drilled to final depth using the cherry. The cherry then describes a number of circular motions (interpolating) milling the cavity to final size. This is normally done in increasingly larger circles, where the cherry is pulled out of the cavity between the cuts to allow for the chips to be blown out (a mill with coolant through the tool is high on my wishlist) Once the program is finished you can measure the diameter of the cavity and if it’s too small you just adjust the program and run it again.”
-Cap’n Morgan http://castboolits.gunloads.com/showthread.php?t=55388
Captain Morgan beware! Your modern sorcery of tools able to move on their own will surely rise up and destroy all humans!
Aha, so that’s another way to do it, not useful to me but it is interesting.
Shrikage rate was listed as being 5/16″ per foot… .3125″/12″ = .02604 or 2.6%
Have since found yet another site that claims 3/16″ per foot…. 1.6%
Are we confused yet?? 😆
Walt… form tool as a cherry…found reference to that today, but heard it from you first. It’s a good idea, and one I’ll have to try out. Thanks for mentioning it. 🙂
As a side note, next time I start a project I’ll have to include a detailed introduction so everyone knows what I’m working with is not the normal and what I intend to actually do. I honestly was expecting maybe 4 or 5 comments and then figure the rest out myself. Never did I expect so many people to jump onto this and go into 5 pages now in just the planning stages. Hope it’s been entertaining thus far for you guys because you’ve been most helpful to me.
Ok, I just had to take a bike ride today it was so beautiful out here. Didn’t get much done today but I’ll update what I’m doing now. I’m taking my own measurements since all I could find online are head/skirt measurements. Gives me a little more insight to the tolerances of real pellets and what works. I haven’t finished but so far I noticed something curious with my JSB rounds. It looks like I might be able to sort them by more than just weight. I noticed of the few I measured so far a couple of them that that two of them measured .2155 x .216 and also matched the dimensions in few in other parts. The other three I measured had two which matched closely. I can’t say for sure unless I took the time to measure a bunch which I won’t. I’ll bet it’s possible to bin them by which die they were swaged from if for some reason you wanted to go into that level of precision. I haven’t seen anybody shoot pellets at 1000 yards so I don’t think it’ll ever be an issue. Most of what I’m doing right now Is not complete. If anybody is curious I’ll post my doodles and measurements when I finish.
As far as how I’m going to do the cut, I’ve been thinking ahead to that a bit, thinking about which drill I’ll use and how I’ll rig it up. I haven’t really told my ideas on how most of this is going to go because I’ll be changing it a lot until I actually do it. That’s a lot to type, and then re-type, and then correct again, etc. I never worked on a project quite like this and since my equipment is very different and ill adept for these purposes, I’ll have to do what I always do and pull a new method out of my… idea hole.
I wont get into too much detail because it’ll probably change but I’ll likely make a frame that mounts directly to the vice and/or to the table around it and suspend the drill above the vice kind of like a non adjustable drill press or overhead router of some sort.
Just wanted you to know I wasn’t actually going to freehand all of this 😆
Powderburner, A .22 cap fires at a much lower velocity than the common LR and would need a tighter rate of twist to stabilize 29 grains. 1:16 in a condor and a .22LR are two very different things because the .22LR is traveling down the barrel at a higher velocity. The faster it goes down the barrel, the faster it spins, the more gyroscopic stability it has. We’ll use a 40gr .22lr 1:16 for example. Now to figure out the RPM it will rotate at punch it into this equation I found on a site V x (12/twist rate) x 60 = RPM. So firing that bullet from your rifle at 1200fps it will come out doing 54000rpm. That’ll put any wooden pull string top to shame. Now fire that same bullet out of a condor (we’ll use my 70fpe as an example) and turn that muzzle energy equation around we get 12.58fps what? Well I fucked that all up. Enough math for now, you get the idea. Theoretically if you feed your Condor Wheaties and steroids every day until it can attain the muzzle energy of that .22lr, you should be able to fire the 40gr rounds with similar trajectory and accuracy.
I’m surprised you managed to shoot the EunJin pellets that accurately, makes me want to re-visit them. From my experience when I used to shoot .177 and from just about every forum, book, and video on the internet, you don’t want to shoot too close to whatever the speed of sound is at your altitude/temp/humidity Since it changes most people usually stay well below but it is worthwhile to experiment anyway.
I decided they were not going to work well once I worked up from 700something-900something and was getting somewhere around 5″ groups if I recall but that just demonstrates what I was talking about, maybe I wasn’t firing them at high enough velocity to give them high enough RPM to stabilize. I’ll bet if you got your hands on a 1:15 barrel you could bring that velocity down some.
Walt, that’s actually pretty damn cool if it’s true. Just goes to show how much damage faking results can cause. That kind of crap pisses me off like no other.
Necrosis, give me a couple weeks and I’ll have pics of what I’m trying, maybe you can build upon what I do. 10,000rpm? With aluminum I don’t know what speed I should use for this particular application. In fact I don’t know exactly what speed it is I typically use. All I know is not so slow and hard that you make cork screws and snap your bit (learned that the hard way) and not so fast you anneal your bit in a cloud of smoke and ire (also learned that the hard way). Figuring out speeds will be in a later step after I’ve made the first cherry anyhow.
I don’t think they’ll ever sell pellet molds unless somebody can make it workable but I would be interested to see you do it in .25 after the results of my .22 experiment is in.
Gippeto, I checked out another source of information that said pure lead loses 1.13% volume upon cooling. http://www.lasc.us/CastBulletNotes.htm Haven’t found a third source to compare but one of the two has to be wrong. Was yours perhaps for an alloy or some other missing factor? Either way that can be addressed when I get to it so don’t worry about it.
Now I’m hearing a lot of talk about Jerry trying to get at me again so I figure I’ll address that one last time. I’m sure Jerry is very good at what he does but all the knowledge in the world is of no help to me if he’s unwilling to help me or will give bad advise just to see me fail. I’ve known people similar to what I know of him so far and I know giving second chances with people is a mistake > 90% of the time.
Jerry if you’re still trying to make me mad and draw me into another pointless argument about nothing, I’m not mad at you. Think of it like this, there is no point in stressing yourself out over me because what am I to you really? Don’t think of me as a person, I’m just disembodied text on a screen and as far as anybody can be concerned that is the totality of my being. Any time you like you can just turn me off or download the blocking script I’m using and mute me so you don’t have to think about it(and have the self control to stick to it). You can find that script under “off topic”. This is the internet, where credentials and opinion mean absolutely nothing. I might be a panel of 12 experimental super mice typing on a keyboard in a secret lab in Siberia for all you know.
I’m really wanting to cast several pellets in clear polyester resin and grind away one half so you can see a cross section of them. Maybe I’ll do it someday when I have a larger selection. Put it with the rest of my bullets and shrapnel fragments as a conversation piece. This is not actually my idea, I’m copying it from http://www.photosbykev.com/wordpress/2009/01/20/air-rifle-pellet-database/ If you haven’t seen the Air Rifle Pellet Database, check it out. About 2 years ago I was talking to that photographer and he was accepting pellets for his database. He might still need a few more donations if anybody cares to help him. He has some cool gimmick rounds like the Sussex sabot and another with a rebated boat tail.
the halves need be apart for the cherry to enter. There is no way to get the ridges on the bullet with the halves clamped.
so for me it would be a boring bar and not the cherry. As you say a roughed out hole to size and then a boring bar to cut the ridges.
After the roughing to get the nose shape I would use a Dbit or half reamer turned to size and shape.
There are a couple different ways to bore molds. The easiest way, conceptually, is to use a single point tool like what Walter is describing. You use a small tool profiled, for, say a single small ridge, and move this into the roughed out hole, cut your ridge, move it in farther, cut another ridge, etc until you get the bullet shape you want. For the one off variety, the usual way is to make a cherry. cherries are not the full size of a round diametrically, but they are the full size of the round lengthwise, thus they are inserted through the top hole of a mold after the hole is roughed in. cherries only cut on one side, like a normal profile cutter. the advantage of using a cherry is that the full profile of the finished product is cut more or less at once and therefore easier to control. but since only one side does the cutting, i pick a steel bar that is slightly smaller than the finished diameter of the round I’m making. I turn the round so that it has the outside relative dimensions that are what I need… like the round I want, but of course its smaller in diameter than the actual round; then use a milling cutter at 90 degrees to the axis of the bar, to cut one quarter of the bar out, leaving a three quarter pie sliced round rod with the approximate profile of the bullet. this is your cherry, the sharp edge of the pie cut is your cutting edge. its inserted into the roughed out hole with both halves of the mold together, then advanced outwards against the walls of the roughed out hole, cutting the profile of your bullet.
walt
the halves need be apart for the cherry to enter. There is no way to get the ridges on the bullet with the halves clamped.
so for me it would be a boring bar and not the cherry. As you say a roughed out hole to size and then a boring bar to cut the ridges.
After the roughing to get the nose shape I would use a Dbit or half reamer turned to size and shape.
Dude, I think everyone is getting hung up on splitting the mold and somehow clamping it down around a cherry that’s the exact size of the finished round; and I don’t know anyone who does it that way. the reason is simple; you can’t control a spinning clamping thingy whatchmacallit. so why even try? the mold DOES NOT require clamping around anything. it only requires UNclamping to release the cast bullet. you are confusing the clamping action with the cherry. these 2 items are for completely different processes. in an environment that requires high precision, you want to eliminate as many degrees of freedom as possible. ergo, the best way to do this is with the mold already preclamped in its finished tolerance, torqued up. when it spins in a 4 jaw on the lathe, it’s not moving at all relative to the axis of the cherry if the cherry is exactly on the centerline of the mold. its only rotation is in the same axis as the eventual bullet, which has rotational symmetry so this degree of freedom (rotation) does not count. this is why precision is necessary. You prebore your mold with, say, a milling bit or undersized drill bit, much the same way as roughing out a chamber in a rifle barrel; then you use the cherry in much the same manner as a finish reamer in a rifle blank, to cut the final chamber dimension.
well back on topic of mold making..
In fact I have been thinking of doing this too!
For .22 or .25..
I too however got stuck in the “cherry” thing as you call it.. I tried to think of things that would let you use notmal tooling.. Maybe on a lathe.. wich is doable… but not consistant at all.
I guess setting the cherry in a mill sort of device.. and then like… push the halves together on the spinning cherry…
As I read here earlier..
However.. while I do own a mill and a lathe…
I don’t own the pushy thingy.
maybe that would be a nice project to build a machine dediccated to making molds!
It’d be a fun project..
I wonder if molds in airgun calibers will sell that well either way..
I guess I need to get a jsb exact solid model first so I can base my own designs on that (BC value drag whatever)
I’m thinking about a machine with the cherry holder dead center.. motor on top… revving real fast.. like 10 000 revolutions per minute.. Maybe higher… (I want aliminium ones really… they cast much faster..)
I might make some crazy drawings tommorow…
laters
the japanese and french and everyone else has quietly been studying it ever since it came out in the 80’s. Only the US turned their backs on it ever since the big MIT fiasco that ‘debunked’ it. Now the name is synonymous with fraud, so they don’t call it ‘cold fusion’ anymore, there are a couple companies trying to rush ‘energy cells’ to the market under various different names.
walt
This Italian ‘reactor’ emits no Gamma. Doubts as to whether it really is cold fusion, but its been comfirmed independantly that it has only 400w going in, and close to 15000w coming out! Could be they have stumbled on a whole new bit of physics. Pretty exciting stuff…..
Oh, for the record, not that anyone will care, but I don’t think cold fusion is a hoax. Never was. The tritium by products were always there, but in minute quantities so scarce that they were difficult to differentiate from background noise and sample contamination. Good thing, too. Otherwise there’d be a lot of dead guys around the world wondering what the hell they did wrong. gamma radiation mean anything to anyone anymore? high energy particles aren’t exactly healthy for you, last time I checked.
walt
- You must be logged in to reply to this topic.
Walt, what you are calling a cherry is called a form tool AFAIK
a cherry has the full shape to it.