Spin casting boolits

[evan price]

Is there any reason why we couldn't use a spin casting machine (or make a facsimile thereof) to get supreme fillout and most density without porosity in out boolits? I'd think in big heavy boolits this might be advantageous. Ideas?

[357maximum]

Seems like alot of trouble when a good ol fashioned ladle works so well.

[lwknight]

+1 on not worth the trouble

[303Guy]

If you folks saw my **** castings with **** alloy you may just think the idea had merit!:mrgreen:

It would work for someone with the means to manufacture a whole set of very near identical molds on a radius wheel. Someone with the desire and means to entertain himself - that's because it would be quite time consuming and require reasonable machinery.

Having said that, there are other means of achieving the stated goal but a spin mold holds a few benefits that go a bit beyond simply getting perfect fillout. Like graded hardness, somewhat more sophisticated nose shapes, radiused heels, not to mention hollow point nose pour's and maybe eight to ten cavities. A high level of sophistication really! (And it would likely be a world first!)

Here is an example of a graded hardness boolit cast in a mold that chills the base quick enough to harden it but keeps the forward part hot long enough to cool soft.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-226F-1.jpg

Fired at about 1800 fps. See how the expansion stops at the hardness change.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-010F-1.jpg

Lube grooves? Who said you need lube grooves?:mrgreen:

[lwknight]

I just can imagine all kinds of logistical problems trying to spincast boolits. It just does not seem practical at all. We do so good with a plain old ladel at little cost.

You got me interested in the gradiend hardness idea.
BTW how do you get that copper color? Last time I looked, copper fortified tin babbet was about $20.00 per pound.

[rob45]

Cast Boolits overtakes NASA!!!

Seriously, I am interested in the graded hardness bullet and more detail on how it was produced.

[lwknight]

Only thing I have so far is just like annealing brass. Stand it in water and heat the nose with a torch.

[rob45]

Yeah, I've done the "anneal the noses" with mixed results. But 303Guy mentioned using a mold to produce the results.

The base is distinctly different in appearance; I was wondering if the lead was the same alloy throughout the bullet and how he did it. No lube grooves indicates a patched bullet; the expansion point is of interest to me because I do a lot of different testing for hunting purposes.

[303Guy]

No lube grooves indicates a patched bullet; No, the seated boolits were dipped into what I call 'waxy lube' which I developed to seat J-word .224 55gr in my hornet with unsized necks using a paper cup arrangement. (That worked pretty good. Around 2700fps in a hornet with 55 grainers sound OK?) Anyway, this stuff is a mixture of candle wax, alox (or any boolit lube) and STP. It's 'tough' enough to stay on in a substancial layer.

I'll have to start a new thread on how I did the graded hardness boolit. (The production rate wasn't fast and I discovered the 'trick' quite by accident. It was a by-product of nose casting). Which is why I see a possibility for spin casting. The trick would be to figure some way of making it work without first developing a space rocket! There is always a simple easy way to achieve the seemingly impossible - if we can stumble onto it somehow!;-)

And yes, it is a single alloy. I now wish I new what exactly that alloy was! I want it back for hunting boolits. It was another one of those accidental things but likely not difficult to reproduce (i.e. any old casting alloy that heat treats). I know it had sinkers in it and range lead and lead pipe and WW's and likely traces of lino-type.

The loaded and lubed round.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-338F_edited.jpg

A hollow point nose pour boolit.

http://i388.photobucket.com/albums/oo327/303Guy/MVC-353F_edited.jpg

Spin casting would make all this easy!
We need ideas to make it happen.:roll:

[rob45]

I'll have to start a new thread on how I did the graded hardness boolit. (The production rate wasn't fast and I discovered the 'trick' quite by accident. It was a by-product of nose casting). Which is why I see a possibility for spin casting.

Great, I look forward to more info on it and will watch for the thread.

I do see the merits of spin casting, but also agree with lwknight concerning the logistics issue; after all, the overwhelming majority of the questions on this forum still indicate that we do not quite have the "old" technology perfected.:smile:

The quest for the perfect combination continues.

[Shiloh]

What a heck of a lot a work!!

I have centrifugally cast silver and even an 18K boolit for jewelry customers.
Doing this for everyday lead boolits is like using a steam shovel to dig a post hole.
What an incredible hassle when the bottom pour works so incredibly well.

Shiloh

[1874Sharps]

303Guy,

You make some incredibly creative and innovative boolits and molds. I remember when I first saw one of your molds -- I had to ask what it was! I would like to see you start a thread on this.

[docone31]

I saw, long ago, a machine that Union troops use to cast with. It was a spin caster! Large one, and not like the one I use in my casting. Much larger, and had an hand crank.
I would think, a swage would eliminate the void issue with much less hassle and cost though.
Shiloh, boy, do I agree with that. Even if they are useing Metal Molds rather than investment, talk about a long day casting! I won't even hint to them about Vaccum!
I will keep doing it the old way. If I want to go to that much hassle, it will be in Gold, or Silver also.
To use spin casting with lead, they would have to keep their molds cold rather than preheat. Either that or keep the spinner, spinning while the lead solidifies. It ain't like silver! Drop a few degrees and it is solid. Lead will have to go further than that.
With the old caster I saw, the molds came off and were replaced with new ones. The lead got poured into the middle and centrifigal force forced it out.
They would put on the molds, spin it, pour the lead, remove the molds, replace with more, spin it, pour the lead, remove the molds, put the previous molds back on the machine.......
Lotta work.

[303Guy]

Thanks for the interesting info, docone31.

This thread has just given me an idea.:idea:

To get the pressure so desired, build a bottom pour pot with a really long pouring nipple (with the valve at the bottom of course) and make the mold to actually seal againt the nipple. That long protruding nipple would have to be heated of course but since I am about to build myself a bottom pour anyway ..... then I can go back to nose pour.[smilie=1:

[leftiye]

If you want to pressure cast an extended spout on a bottom pour would give more pressure the longer the spout was. Spout would have to be heated though. Even this would seem to be more trouble than it would be worth. Even when contact pouring with a bottom pour, the pressure often is too extreme and fins result.

There is no guarantee that spin casting would work at all anyway. The molds are heated and the metal put in under pressure, and then allowed to cool. With anything but pure lead, this should result in radical frosting. Swaging as has been said, would remove voids more easily, and more surely. And make shinier boolits!

[Blacksmith]

Using centrifigual force to force metals in a mold is a common practice in industry. There are many different processes but the one that probably would work best for boolets is called Spin Casting or Centrifugal Rubber Mold Casting; Google either term in quotes will get you more information. The drawback is manufacturing equipment cost although mold cost per cavity would be lower and production rates would be higher.

Here is a link to an equipment supplier for an idea of prices:
http://www.contenti.com/products/spin-casting.html

This is a link at another suplier to their 13 minute video describing the process:
http://www.tekcast.com/i16//information.html

Blacksmith:cbpour:

[357maximum]

You could try casting on a merry-go-round whilst someone spins it really fast....personally I lack the coordination so I will let someone else try it.

[evan price]

What got me thinking about this was looking over the debacle with Cap'n Morgan's shotgun buckshot moulds.

I was thinking, on something that would need the sprue cut anyway, making up a rubber mold pattern for buckshot like the Cap'n Morgan "Bunch of grapes" style would work very well in spincasting.

Also, you could nose-pour large boolits in that style, too.

You could also have good fillout with a harder alloy, such as a zinc-rich (or zinc-contaminated!) lead.

My only concern would be the ability to rapidly service the molds between pours.

I also have worked on a hot-swaging process that used a three-piece mould; useing high pour temps, you pour your cavity, leaving a puddle that fits inside a depression in the mold blocks- the upper part is placed on top and then squeezed or struck, compressing the lead in the mould.

I used to build machines that injection-moulded molten aluminum to make engine blocks.

I wonder if that sort of idea would work for boolits.

[303Guy]

evan

We need to talk about that hot-swaging process you mention! I long time ago I wanted to do that but never got a 'round tooit' but I was thinking about it this morning. I have also thought of a three piece mold.

Injection molding - Mmmm.....!


Even when contact pouring with a bottom pour, the pressure often is too extreme and fins result. leftiye

I am thinking along the lines of a solid body straight sided boolit with nose pour in which the only air escape is between the pouring nipple/sprue plate and mold nose. The problem I have been having is getting the alloy into the mold fast enough for it to fill out without chill wrinkles and to have a reservoir of molten metal to take up the shrinkage. Now with a 'pressure pouring nipple'. My hollow point mold arrangement might just work without any sprew to cut off or remove.

Another idea would be to roll form the boolit between three rollers that closr in on rolling and squeeze out an trim off any excess alloy. This would mean casting an oversize cylindrical slug and rolling it into shape and size.

I do agree that the engineering required would be quite an undertaking but the 'spin off' ideas make it an interesting topic. Having said that, I don't see why a simple four cavity radial split mold with a small casting well and a square punch type sprue cutter which would be operated by spinning up to speed, pouring in the alloy from a ladle, waiting for the sprue to solidify, stop the spin, split the mold and dump the castings, close, spin up and repeat. In principle, no different to any other split multi-cavity mold. There are low voltage DC motors that have tremendous start up and stopping torque, ideal for the purpose.

[Southern Son]

So not only do I have to hold the ladle against the sprue plate as I rotate both to an up right position, I have to do it while spining around in circles????????:bigsmyl2:

[Tom W.]

IIRC, that's how Mann's bait Company used to make worm sinkers, using two big rubber (or silicone) discs and spinning them, while somehow introducing the molten lead.

[deltaenterprizes]

What do you figure the cost per boolit would be ?
If it was cost effective don't you think the big bullet makers like Speer and Hornady would be using it?

[303Guy]

With high pressure, high speed swaging equipment and tight lead alloy control I would guess there would be no hope of spin casting viability. But try swaging harder alloys. Can be done but the alloy cracks. Anyway, I would think it would be easier (and cheaper) to build a high production rate cast swaging machine.

Now at the home casting level, things change a bit. Maybe a hand operated cast swaging press would be do-able?:roll:

What I had in mind was a top punch that come down through the molten pool and close off the top of the mold while the alloy to freezes under pressure, then the bottom punch pushes the boolit up for removal, pretty much like a lubri-sizer. Or if a split mold is required, then simply have an opening mechanism.

[leftiye]

303Guy, You've walked headfirst into one of my favorite thangs. Try heating your mold on an electric hotplate or other heater. Sounds like that should solve your problem - lead hitting the mold won't cool so fast - so it won't wrinkle. Rest of boolit will cool slower too. Work setting the molds on the heater in to your routine/sequence of operations in casting. I drop the boolit, set the mold on the heater, inspect the booits, fill the mold again, etc.. Not a method that a lot like, but it does help with the cold mold blues.

Put a piece of 1/4" plate on the hotplate. Cut one side out of a 1/2 gallon tuna can and turn it upside down on the 1/4" plate, set the mold inside the oven thus created.

I'm assuming you have seasoned the inside surfaces of the mold. This and coating the mold slows heat transfer out of the metal, and allows the mold to cast cooler.

[rob45]

But try swaging harder alloys. Can be done but the alloy cracks.

Exactly.

This is one of the reasons why manufacturers of jacketed bullets control expansion characteristics through jacket design; they are somewhat limited with the alloy.


A reference can be found in Sierra's 5th edition reloading manual.

For their #3000 (.375" 300gr Spitzer Boat Tail) GameKing, they state: "A very hard 3% antimony lead alloy core is inserted...".

For their #8830 (.4515 300gr Jacketed Soft Point) SportsMaster, they state: "Despite its soft point title, this 300 grain #8830 Jacketed Soft Point SportsMaster is the single hardest bullet Sierra has produced. Utilizing a 6% antimony, 4% tin, 90% lead alloy core,...".

Both of these bullets are designed for truly heavy game- limited expansion at high velocities (375 H&H, 378 Weatherby in one; 454 Casull in another).
But 3% is "very hard"??? 6% is "the hardest"??? At the time I knew very little about the swaging process, and called Sierra for explanations.

Due to bullet shape, the amount of swaging that takes place is considerably more with the rifle bullet, hence the lower percentage of antimony. Sierra makes up for that by using their heaviest jacket cup.

According to Corbin, "hard" lead for swaging is anything above 10 BHN. Assuming the same shape, doubling the BHN of the alloy quadruples the pressure required. And the dies that handle those types of pressure are considerably more expensive, not to mention that the pressures involved can easily exceed the capabilities of a hand-operated press (think Uber$$$ hydraulics).
http://www.corbins.com/lead.htm

Since we are talking about the ultimate cast bullet designs rather than jacketed, we naturally tend to adjust our alloys to achieve desired characteristics. When discussing the possibility of swaging, not only are we limited by behavior of the alloy (cracking, shearing, etc.), but we are also limited by equipment capabilities. Sure, the proper equipment can be made for nearly any application. But at what cost? At such costs we may have already exceeded the costs of spin casting. Even if cost were not an issue, we still have to deal with alloy behavior.

If I am understanding correctly, the idea of combining casting with swaging may indeed hold merit. Are you talking about a process similar to that used by Speer?
How would it be done without trimming the finished bullet, meaning a sprue? The pour would have to be very precise so as to eliminate having to bleed excess (and thereby eliminate the need for trim).

[lwknight]

Are we talking about spin casting for mold fill or is it to increase the gravity to better expell any possibly trapped air. I didn't know that trapped air was an issue as long as the vent grooves were clear and pressure casting is easy. To a point anyway.

Spin casting sounds cool and all but, whats really to be gained?

[rob45]

We are discussing the possibilities of bullet designs not easily obtainable with conventional cast bullet molds. See post #4 by 303Guy.

[Blacksmith]

Watch the video in the link referenced in post #16. Now imagine how many boolits you could fit around the circumference of the mold disk you could probably have a double row with channels leading to each one it would look like spokes on a bike wheel. The boolits could be either nose pour or base pour could be hollow point maybe cast in place gas checks who knows. Best thing the molds would be made from metal boolit masters that could be turned on a lathe or made from existing cast boolits. The rubber is vulcanized around the metal master so the per cavity mold cost would be much less. I would guess you could get close to 100 boolits in a 15" diameter mold more in larger diameters. If you had two molds of 100 each and cast one while unloading the other you would make a lot of boolits very quickly.

Of course it would take some development work and capital equipment cost but it is probably do-able. Not practical for home use but for a small volume comercial caster it might make sense. You would have to compare costs of spin casting vs swageing unless there are specific properties of one or the other process you want. You might be able to get a spin cast equipment maker to do some test runs for a reasonable price to prove the concept.

Blacksmith

[303Guy]

How would it be done without trimming the finished bullet, meaning a sprue? The idea would be for the 'swaging' pin to enter through the molten alloy puddle and seall of the mold, thus trapping liquid alloy in the die and holding that trapped volume under pressure as it solidifies. For a nose pour the ejection would have to be downward. Not sure how well the air would escape with nose pour.

Thanks for the mold heating 'oven' idea leftiye. It's one of those simple yet brilliant ideas where one says "now why didn't I think of that!":-)