Ceramic Bullet Moulds

[tonyjones]

Hi all,

I was recently reading Glen Fryxell's book From Ingot to Target... and he mentioned ceramic bullet moulds. Does anyone here have any knowledge of or experience with them?

I am intrigued.

Regards,

Tony

[a.squibload]

Never seen any.
I don't buy ceramic knives, afraid I'll drop one.
Not that I would drop a mold, but it would be a shame if it ever happened
and shattered all over the place!
Would probably be easy to get the mold up to temp, if that's even necessary with ceramic.
Good topic.

[onondaga]

Machinable ceramics are used in dentistry. There is a computer aided machining system that carves a machinable ceramic material into dental crowns. This existing technology would be a reasonable place for an inventive person to start.

Coming from the dental technical industry, I can tell you that the dental system for these crowns is franchised and heavily protected with patents for the dental applications of the system and it is a very significant investment for a dental laboratory to become involved in providing that particular service . I believe over $20K.

Machinable Ceramics Material search:

http://www.google.com/search?q=machinable+ceramics&hl=en&tbs=shop%3A1&aq=f

The stuff is available for experimenters.

Member PatMarlin could probably run this stuff in his shop. Hopefully after he finishes my PB45 CheckMaker!!!!!

Gary

[fryboy]

years ago they used various stone , even to make silver molds - the lost wax process is still used today , ceramic is kind of a stone , i'm not to hip on various umm ceramic alloys/compositions but i do know that there are some tough ones

[shotman]

hey you could make a lot and fill all and let cool and just break them to get the boolit out
they used to make cannon ball molds out of clay. and fire them. made a {brick} mold and fill and let cool and crack the shell

[tonyjones]

Gary,

Thanks for the link. I found some interesting reading there. Ceramics have some interesting properties: tolerances to .0005", temperature stable to 3,000 degrees farenheit, machineability,
etc.

I have some experience with ceramic pigments (oxides of various metals) in chemical coatings, however, this application is totally outside my comfort zone. I am not a machinist and probably never will be. That said, I'm still interested in this topic and hope that more members will find this thread and offer their thoughts and experiences.

Regards,

Tony

[HollowPoint]

When I first mustered up the gonads to attempt to make my own bullet molds and I was looking for information on the best/easiest materials to use, I wondered about the possibility of using ceramics.

Beyond the possibly overly fragile nature of ceramics, I can see no other drawbacks from using this material except maybe the cost and availability. I had no idea that machinable ceramic material was made.

I had just assumed that if a fellow really wanted a ceramic bullet mold, the mold itself would have to be formed in some other type of mold; like a ceramic bullet mold, mold.

I really hope one of you guys delves into this a little further and keeps the rest of us posted.

HollowPoint

[Johnch]

I saw a guy making lost wax ceramic a while back
They were for small parts

But I could not see why you couldn't make boolits in them

But to do any production , you would need a mold for the wax LOL

John

[geargnasher]

I had the idea when I worked for Boeing years ago, there are materials in the aerospace industry that are astonishing. My dream was to build a car engine out of polymer plastic with ceramic cylinder liners, but the most practial thing I tried was making a roundball mould out of common clay and had a friend fire it for me. The main issue there was getting it dry enough to cast, and I never made a sprue cutter that worked very well, so I just used wire nippers to cut the sprues after they were cast.

Gear

[Pavogrande]

Ceramic cylinder liners: About a hundred years ago a company called John Bean came up with exactly this solution for their orchard sprayer pumps - The spray compound of the day had a very high sulphur content and was too abrasive for standard cast iron --
old man's memories --

[Von Dingo]

Basically how investment casting of firearm parts is done.

[R.M.]

I'd have to wonder how well the ceramic would dissipate the heat. Might take longer for the alloy to set-up.

[Simonpie]

In the hot rod world it is pretty common to spray a ceramic layer on steel or aluminum as a heat barrier. It won't necessarily get you what you want out of a full ceramic mold, but would be a good way to tune the warmup time and casting rythm. It also has a bit of thickness, 1-5 thou, so it might be a way to "shrink" an oversize mold, or, just do the parting faces to "grow" an undersize one.

[MikeS]

Basically how investment casting of firearm parts is done.

Investment casting is the 'hi tech' name for lost wax casting. Basically they make a mould that casts the wax core(s). Then they take the wax core, and coat it with a liquid ceramic that is very fine grained. when that dries they coat that with a coarser ceramic, and do that again a few times until they have the mould the external size they want. then this whole mould (or would it be mold?) is heated so the wax core melts out, leaving a mould that is almost exactly the part they want. Then they fill it with the steel, or whatever material the finished product is made of into the mould, and once it cools, they break open the mould. The expensive part of the process is the moulds to make the wax master. Once that is done, making the parts gets very cheap.

When I was in the leather machinery business years ago, we had several parts that used to be made from drop forgings that I went ahead and located a firm that did investment casting, and made the parts that way. The original drop forgings were made from 1014 steel which is a low carbon steel, and also a very old grade of steel. (our machine was designed in the 1880's) With the investment castings, we used 8620 steel which has a much higher carbon content which allowed for much better hardening. The old 1014 steel when case hardened the outside would get very hard, to a Rockwell hardness of C60 or higher, but the internal steel stayed relatively soft. The 8620 steel when case hardened would also get to C60 or so to a depth of .015" just like the 1014, but the difference is that the core would also get hardened to about C40 or so (rather than the C10 that the soft core of the 1014 was). What this did was make a part that was very resistant to wear from being beaten by another part. The first part we made this way was the bobbin case of our leather stitcher which unlike a home sewing machine which goes around in circles, this one was a 'shuttle' in that it went back and forth along a track, and the part that moved it wasn't attached to it (the thread had to go completely around the shuttle), so it would get worn at the contact points. We had stopped making this part in the US back in the 1950's as it was too expensive to machine the drop forging, and get the heat treating just right, and had them made in Japan since then. I was able to setup a complete machine shop, get 1000 castings, and machine 100 of them for the same money the Japanese wanted to make 100 of them! One of the nice things about investment castings is they're highly precision, and we were able to make the shuttles so that they needed very little machine work to make a completed part, all the contours that years ago were machined from a very rough drop forging were now done right in the casting, about the only machine work was drilling a few holes, and tapping a few screw holes, then heat treating them.

To make a boolit mould via investment casting could be done, it would probably be a mould that would cast 25 or more boolits per mould, but the initial tooling to make the wax masters would probably cost over $5k so it wouldn't be feasible to anyone but a commercial caster that sold LOTS of bullets. On the other hand, by using investment casting, shapes that would be hard to make, or impossible to make via conventional casting (square grease grooves come to mind, or odd shaped hollow points) could be done very easily.

Sorry for the long post, it just that this is something I know about (and still remember!). If anyone is really interested, I could post some pictures of the part we made, along with the original raw drop forgings, the raw investment castings, and the finished part, as I have a small sampling of these that I kept from years ago.

[c3d4b2]

I do not know if this will be an issue using ceramic for moulds or not...

We make hybrid circuit on ceramic substrates at work. One of the issues we have is the ceramic will crack if it is heated up to fast. I do not know if a mould would have the same issue, however it would be worth doing a quick check.

[onondaga]

Machinable ceramics eliminate the need for investment casting or building up sand castles and firing them into glass. They machine like aluminum, brass or Delrin and could easily be made into boolit moulds by a competent machinist. The link I gave above lists suppliers that stock rods, dimensional stock materials for machining.

One of my RC planes has a Russian glow engine with a machined cylinder liner in the head.

Gary

[a.squibload]

Investment casting for boolits has been discussed here in reference to silver boolits.
My wife makes jewelry, said it would be hard to get an accurate diameter.
Maybe she just doesn't wanna do it...

[theperfessor]

I can see the benefits of ceramic molds of various types for high temperature casting, but what characteristic(s)/benefit(s) would they have for low temperature casting of lead alloys? What would make them better than the ferrous/aluminum/brass molds currently used?

I don't see it, but I've got an open mind, so someone make a clear statement of superiority for me please.

[tonyjones]

Gary,

I think that machinable ceramic would be the way to go. Tolerances to .0005" and machining with common carbide tools. I really have no idea what the cost would be to get set up to do this. For an existing mould maker it might be little more than minor tooling costs and dealing with the learning curve.

theperfessor,

As I stated, this topic is well outside my expertise. I started the thread because I'm curious and wanted to see what discussion would ensue. Could it be that:
A quality ceramic bullet mould might/would cost less than aluminum/brass/iron?
A ceramic mould would have superior release characteristics?
A ceramic mould would not be subject to contamination/bullet deformation from oils/sprue lube?
Mould temperature would not be critical to obtaining well formed, uniform bullets?
Etc.?
Corrosion resistance vs. iron.

There would be disadvantages as well such as not as durable as metal. However, it's probably not a good idea to drop ANY mould 3 plus feet onto the concrete floor.

This may or may not be a workable idea. However, I would like to hear and learn more. Perhaps someone with the talent and equipment would be willing and interested enough to make the attempt.

Regards,

Tony

[onondaga]

Ease of machining is a good one compared to steel or iron

Coefficient of expansion is a key benefit when selecting ceramics for mold materials. The amount ceramics thermally expand and contract is statistically nil at bullet casting temperatures.

Fine finishing of mold surface is likely easier with ceramics.

Less weight than Ferrous.

Ceramic mold cavities would be very non-stick/bond for lead alloys

A composite mold design would conquer the sprue cutting challenge with metal mold tops attached to the blocks and sprue plates pivoted to the metal mold top.

Gary

[bowfin]

I have heard of people machining bullet molds out of graphite.

[uscra112]

Have worked a lot with alumina ceramic as used for structural elements of high-precision measuring machines. (You come in contact with alumina ceramic every time you handle a spark plug.)

In the sense of the split permanent molds we use, ceramic would be a poor material. It has a very low rate of heat transfer, so it would take far too long for the poured boolit to solidify. The more you cast, the worse that would get. Getting good castings is all about extracting the heat of the molten metal so that it solidifies into a uniform mass that fills the mold. Slowly enough that bubbles can escape, and so the wrinkles that iron founders used to call "cold shuts" don't form, but quickly enough to get a decent rate of production. Ceramics would fail on the second count.

Ceramic is extremely stable dimensionally, however, and because it is a friable material it can be machined and lapped to incredibly small tolerances. We could get bars six or eight feet long that were lapped straight, flat, square and parallel to a few microns - one micron being 40 millionths of an inch. Interestingly, one of our suppliers was Coors. Alumina ceramic is a prime material for glass-making machinery, and they use a lot of glass.

My experience with "castable ceramics" is quite limited, but from what I do know they are not very strong.

[theperfessor]

Well, I hope I didn't come across as being down on the idea. My background includes a certain amount of product development work. I know that there are a lot of processes, and a lot of materials, that can be used to make a product. And I have no doubt that a ceramic mold can be made for bullet casting. In other words, it is technically feasible.

But my gut feeling tells me that with the ceramic fabrication techniques available right now, the cost of making a ceramic mold, either singly or in volume, is still going to be much higher than an aluminum, brass, or ferrous mold. I don't see the technical advantages making up for the price difference, and I see some technical shortcoming with ceramics that would have to be considered also.

Is this any reason not to try it or talk about it? Not at all! Because somebody may well come up with a material and/or fabrication technique that would change the calculus of the situation enough to make it financially justifiable.

As a manufacturing guy it's just my way of looking at things.

[tonyjones]

theperfessor,

I come to this forum to learn. I contribute where I can but so far I've gained far more than I've given. There are myriad personalities and knowledge levels among the members here. That said, I was hoping that you would jump in here.

Regards,

Tony

[theperfessor]

Let me throw this out as a factor that could change the "calculus of the situation". If we ever have to start casting out of zinc instead of lead a mold material that can withstand the higher temperatures needed would make ceramic molds a more economically viable proposition.

There are also some newer ceramic fabrication techniques that show some promise in reducing cost and increasing production rate that might also tilt things a little more in favor of ceramics.

Ceramics as a material family include a lot of different materials, from tungsten carbide to various glasses and carbon products. Some are so hard they can only be machined by grinding with diamond tools, others are friable enough to be machined with carbide tooling. They also vary in toughness and shock absorbing ability.

Right now there just aren't any ceramics that combine all the properties needed to make competitively priced bullet molds. Which is no reason to not think about them; it is instead a good reason to do research that would deal with the problems ceramics have in this type of application in order to improve the materials and processes used to make them.

In order to improve something a frank appraisal of the problems that currently exist is always the first step of the process. This is not a negative mindset, it's an intellectually honest assessment. Then the problems can be systematically dealt with.

[Centaur 1]

Perfessor, I was thinking about carbide, then you mentioned it. I bet a modular molding system would work. It could use a brass or steel mold body that has pockets machined that will accept carbide inserts that have the boolit shape molded into them. You could have a mold body with 3 or 4 pockets machined in, and you could put in any combination of inserts for whatever boolits you needed that day. Just think of the possibilities if one of the major mold manufacturers teamed up with a company like Kennametals for the carbide inserts.

[TRX]

I was thinking more along the line of making a steel "bullet" on a mandrel, then using it to impress two blocks of pottery clay, similar to a cherry between two metal blocks. Separate the clay blocks, fire in a kiln.

You might need a threaded insert to hole the sprue cutter, and you might want to machine the top flat before firing.

What I was thinking of, was that this would avoid having to make and use a cherry, or use a CNC lathe with boring bar. All you'd need is a lathe to make the mandrel, basically.

Even if the pottery mold didn't last long, it would let you experiment with bullet shapes, grease grooves, etc. for a very low price, and you could have one of the custom mold makers duplicate your successful shapes in a metal mold.

[runfiverun]

i worked in electro-ceramics for a few years their process might prove out better than the full machining route.
lead [and other oxide powders and binders] oxide powders are mixed wet and spray dried, this is then compressed into shape and then kilned.
[a cherry could be inserted and pressed into the initial part] the two halves would be cut apart, and then a machining is done on the part for final cavity sizing and for the handles.
consistant materials and cnc machining would produce final, repeatable, and mixable halves.

[turbo1889]

This post deleted by original poster.



I am in process of deleting everything I have ever posted about casting with zinc because I have decided I will not share any of the knowledge I have learned over the years about casting with zinc due to the bloodthirsty prejudiced posts of some members on this forum viciously attacking those who cast with zinc. I will not share my knowledge with the enemy.

[a.squibload]

Even so, it sounds better than whittlin' boolits out of ingots.

Anybody got a band-aid?

[Cap'n Morgan]

Ceramics has a low thermal conductivity, which is one of the reasons they work well for investment casting molted steel. The steel must stay molten long enough to ensure a proper fill-out. For the very same reason I think ceramics would be a poor choice for a boolit mold - The cooling period would be too long.

[runfiverun]

if there were inserts of aluminum or steel, the heat migration would be greatly increased.

[Suo Gan]

Not trying to make fun, but what is wrong with aluminum, cast iron, or brass? Easy to machine, easy to use, not that expensive. This is reinventing the wheel to me. I have some ceramic balls that my dad used to fire rockets into at the test site. You can see where they took a direct impact and are still in one piece. Ceramics are amazing, but I don't think this is the right set of circumstances to deserve much noggin time. To me at least. If the argument is for shooting zinc bullets, which has some merit I grant that, mainly because they do not need lube. But zinc alloys have always run several times the price of lead alloys. I have been selling my zinc wheel weights. I have even traded them one pound of zinc for three pounds of lead.

Anyway, best of luck, certainly hope we will not have to be shooting zinc anytime in the near future myself.

[uscra112]

Gee, maybe there's a use for my boxful of wornout AMAL carburettor bodies after all.

[Southron Sanders]

Brass Moulds are much superior to Aluminum Moulds-but Aluminum moulds dominate the market. WHY? Because Aluminum is so much cheaper than brass.

Unless ceramic materials fall to the price of aluminum or lower, I don't see any future for ceramic moulds rather than for custom moulds where the customer is willing to spend a lot money for such a unique mould.

It always goes back to economics-just like about everything else in life.

[Echo]

It's outside of my skill set, but it seems to me that the ceramic wouldn't absorb the heat from the alloy very fast - so the boolit wouldn't set (freeze?) very fast. ???

[garym1a2]

Try BeO ceramic (Berilum Oxide), it has very high thermal conductivity. Very expensive material.

[Willbird]

I have heard of people machining bullet molds out of graphite.

I have always wanted to try making one from EDM graphite.

[Blacksmith]

I have some experiance in Lost Wax casting and the manufacture of ceramic reinforced metals.

The raw material cost of Machinable Ceramics are not cost effective when compared to conventional mold materials. Unless there is an offsetting advantage in properties aluminum, brass and steel are cheaper. Here is a source of four types for you experimenters:
http://www.mcmaster.com/#machinable-ceramics/=ehc1lv

Lost wax would work but with a higher production cost because of more steps and more consumables. The one niche Lost Wax would be good at would be for testing designs. The jewelry industry uses valcanized rubber or silicone rubber molds for making wax patterns. You could machine a metal pattern Boolit, make a rubber mold inject wax patterns one at a time then assemble many patterns on a wax sprue tree and invest (coat with ceramic) that then burn out the wax and cast a few dozen or few hundred for testing. If the design worked go ahead and have it machined in a metal mould.

Pottery molds would also work but the down side is some pottery ceramics shrink quite a bit in firing. Boolits may be too small to matter but you would have to watch that and maybe oversize the pattern.

Back in the black powder days some round ball moulds were made from slate or soap stone. Jewelers have cast silver and gold in Tulfa (a volcanic pummice), Cuttlefish Bone, and sand moulds. Another casting process that would work is Spin Casting in rubber molds, widely used with lead and zinc alloys, here is a link to one equipment manufactor:
http://www.conquestind.com/spin_samples.php

Blacksmith

[Willbird]

There is also lost foam to consider. The molten metal in some cases burns out the foam, not so sure about that for bullets. I know they use lost foam for sand castings, not sure about investment castings. The castings from lost foam sand castings are awe inspiring in their detail. The stuff we worked with used styrene bead type foam, not sure if you can use a closed cell foam or not. One thing about those metal parts however, they can be a bear to machine because they have a thin layer of the ceramic on them...and one time they tried recasting the chips from the process, and the result was a casting that ate every PCD(poly crystalline diamond) tool in the process within 10 parts...maybe not good going down a rifle barrel :-).

Bullets are usually cast in what would be called permanent molds...one benefit is that they are more consistent, a lost wax part is a casting from a mold that is usually made from a casting from a permanent mold...one more layer of process. One interesting possibility however is to make the mold for the wax part, on a 3d "printer" that will assemble a plastic part from a computer program.