Sand Cast vs Wax Cast Brass
- Thread starter Hoyt
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Can't answer, but here is a bit of advice I have found to be true over the years.
:m2c:Sand cast is true brass, the wax cast is almost always bronze.
The soft yellow sand cast brass is a dream to work, soft as butter, can be easily annealed it if should work harden.
The non-malleable wax cast bronze, I have came to develop a genuine hatred for it. Hard as the hinges on the gates of Hades, very unforgiving, can crack or break if attempting to work it even a little. I have learned to never attempt heating it for annealing.:curse:
So in short, two strikes against the wax cast, price and ease of working it.
Sand cast is considerably rougher as it comes out of the mold than wax cast and thus requires a lot more material removal to get it to a polished state. Wax casting is also quite a bit more expensive just from the mold making standpoint. Not sure if TANSTAAFL is correct or not in the brass vs. bronze question but it stands to reason. Those foundries doing lots of lost wax investment casting are catering more to an artistic/marine type of clientele and would most likely be working almost exclusively in bronze. From a purely visual standpoint there's very little discernable difference in the two metals. TANSTAAFL is most definately correct in the hardness and hard to work observations though. Bronze is much harder and much more brittle than pure brass. Bronze's only advantages over brass are it's greater strength and it's superior resistance to salt water corrosion, neither of which are particularly desirable in a muzzleloading gun.
Dick
Dick
I have a brother-in-law who does the wax castings for bronzes, the artistic stuff. It takes a good bit of time to set up the moulds but the details are incredible.
I made sand castings of trigger guards and butt plates, it's not too difficult, but they take a lot more time to file out than wax castings.
I had my brother-in-law make up a few wax castings for me and he used soft yellow brass. They came out beautifully and only needed a little filing with a fine file and then polish.
I would guess the extra cost comes from the cost of equipment, time to set it all up, plus you are paying a little more for the time you will save.
Regards, Dave
I made sand castings of trigger guards and butt plates, it's not too difficult, but they take a lot more time to file out than wax castings.
I had my brother-in-law make up a few wax castings for me and he used soft yellow brass. They came out beautifully and only needed a little filing with a fine file and then polish.
I would guess the extra cost comes from the cost of equipment, time to set it all up, plus you are paying a little more for the time you will save.
Regards, Dave
Just an observation here, but brass has a melting point of roughly 898.88 degrees Centigrade, whereas wax melts at 54 degrees Centigrade...
Wouldn't the molten brass alloy melt and distroy the wax mold?
I believe the rough texture of the sand cast mold is caused by the moisture in the sand being boiled off by the molten alloy...
Yes it's called lost wax casting. The wax is poured into a master mold then is use to make a cavity in the mold that the hot metal is pour into. When the mold is cured the wax is melted out before the hot metal is poured in.
Or something like that.
Lehigh..
Remember, the oldies were sand cast. Which would be correct to recreate an original longrifle/fowler. If you are anal, and making a pristine-perfect gun, never be used, wax cast is the way to go. Eric Kettenberg, and others who build guns that look like antiques, select brass furnature with flaws(voids) to recreate this look of the originals. I do use the wax cast on steel mounts. ::
I have some knowledge of the lost wax casting process, having worked decades ago with the medium in precious metals casting.
This was the way we did it back in the early 70's: A mold is made (usually from latex then) of original master model. Mold parting lines were cut open and model was removed. Molten wax under pressure is injected into said rubber mold, quickly cools and wax casting removed. Wax casting is then adhered by it's sprue to a central wax trunk (is then called a tree) along with one, or several others.
Bottom of tree is adhered with hot wax in center of a rubber base, which also acts as a seal for one end of a open ended metal cylinder container which is placed on a vibrating table. Liquid plaster of paris like material is poured into container over the tree while container is vibrated to remove bulk of air bubbles, often container is then placed into a vacuum chamber where any remaining entrained bubbles are removed from liquefied compound.
Plaster quickly sets up, rubber base is removed, (bottom of wax trunk is now exposed) container is then placed into an oven and brought slowly up to heat, plaster now cures hard, wax is melted and cleanly burns out, leaving a void, which now becomes casting mold for the molten metal to come.
Container is still hot when removed from oven, it may, or may not (might be just gravity poured) be placed into a centrifuge with a crucible affixed in such manner for molten metal to be injected (into opening left by now burned out tree trunk) under G-forces into plaster mold while spinning.
Container is removed and cooled down, plaster is removed from container and the casting, metal castings are cleaned up with brush and high pressure water, casting sprues were then cut off tree and casting was ready for use.
This was the way we did it back in the early 70's: A mold is made (usually from latex then) of original master model. Mold parting lines were cut open and model was removed. Molten wax under pressure is injected into said rubber mold, quickly cools and wax casting removed. Wax casting is then adhered by it's sprue to a central wax trunk (is then called a tree) along with one, or several others.
Bottom of tree is adhered with hot wax in center of a rubber base, which also acts as a seal for one end of a open ended metal cylinder container which is placed on a vibrating table. Liquid plaster of paris like material is poured into container over the tree while container is vibrated to remove bulk of air bubbles, often container is then placed into a vacuum chamber where any remaining entrained bubbles are removed from liquefied compound.
Plaster quickly sets up, rubber base is removed, (bottom of wax trunk is now exposed) container is then placed into an oven and brought slowly up to heat, plaster now cures hard, wax is melted and cleanly burns out, leaving a void, which now becomes casting mold for the molten metal to come.
Container is still hot when removed from oven, it may, or may not (might be just gravity poured) be placed into a centrifuge with a crucible affixed in such manner for molten metal to be injected (into opening left by now burned out tree trunk) under G-forces into plaster mold while spinning.
Container is removed and cooled down, plaster is removed from container and the casting, metal castings are cleaned up with brush and high pressure water, casting sprues were then cut off tree and casting was ready for use.
With investment castings, as was mentioned, there is a master tool which has a cavity that is the exact opposite of the finished part. This mold cavity may have "runners" built into it which will form the channels (gates and risers) which the metal will be poured during the actual metal casting phase of the process.
Those of you who have built plastic models are familure with these "runners" which feed the plastic into the mold.
Wax is poured or injected into this cavity and allowed to cool.
The wax is then removed from the cavity and coated with a ceramic slurry, about the consistancy of thick gravy. Not all of the wax "runner" will be coated. Not coating all of the runner will leave a hole or "gate" in the ceramic for the wax to melt out of, and the metal to be poured into.
When the ceramic is fairly hard, it, and the wax inside of it will be placed in a furnace.
This furnace will melt out the wax, and harden the ceramic driving all moisture out of it.
The Brass or Bronze will then be poured into the ceramic mold thru the "gate" left by the runner and left to harden. When the metal is hard, the ceramic mold will be broken off of the casting.
These castings will be exact reproductions (although slightly smaller) of the wax which formed the cavity in the ceramic.
The reason I went thru this description is to give folks a feeling for the reason investment castings cost so much more.
As for why Bronze is used, rather than brass, I don't have the foggiest idea. Both are easily cast, and the best reason I've heard so far was given in the post above. (Marine casting houses have the fancy equipment to make investment castings in commercial quantities).
I have found that annealing Bronze using the same methods used for brass does work (Water quench) although the bronze will never be as soft or mallible as brass is.
I also found that you want to anneal German Silver using the same methods as steel. (Slow cool).
Those of you who have built plastic models are familure with these "runners" which feed the plastic into the mold.
Wax is poured or injected into this cavity and allowed to cool.
The wax is then removed from the cavity and coated with a ceramic slurry, about the consistancy of thick gravy. Not all of the wax "runner" will be coated. Not coating all of the runner will leave a hole or "gate" in the ceramic for the wax to melt out of, and the metal to be poured into.
When the ceramic is fairly hard, it, and the wax inside of it will be placed in a furnace.
This furnace will melt out the wax, and harden the ceramic driving all moisture out of it.
The Brass or Bronze will then be poured into the ceramic mold thru the "gate" left by the runner and left to harden. When the metal is hard, the ceramic mold will be broken off of the casting.
These castings will be exact reproductions (although slightly smaller) of the wax which formed the cavity in the ceramic.
The reason I went thru this description is to give folks a feeling for the reason investment castings cost so much more.
As for why Bronze is used, rather than brass, I don't have the foggiest idea. Both are easily cast, and the best reason I've heard so far was given in the post above. (Marine casting houses have the fancy equipment to make investment castings in commercial quantities).
I have found that annealing Bronze using the same methods used for brass does work (Water quench) although the bronze will never be as soft or mallible as brass is.
I also found that you want to anneal German Silver using the same methods as steel. (Slow cool).
If considerable time and creative talents have been invested (pun intended) into making a master wax model. I for one would not wish to use it for just a one time casting attempt, which may result in a good casting, or maybe, a complete loss of everything.
I would make a rubber mold of the model to obtain wax castings, then if a snafu occurs during metal casting, it is just a simple matter to redo.
Your simplified version of making and using a plaster mold spooks me a bit. If the plaster mold has not been thoroughly heated to remove all moisture, it could get downright exciting when one pours in the molten metal.
Thanks to everyone who gave a detailed description of the wax cast process. While I knew a little such as using a ceramic slurry to make the actual mould, the other details are much appreciated. It also explains why the butt plates my brother-in law made for me were smaller than the original I sent him to be duplicated.
TANSTAAFL: Your description brought to mind the first time I saw a wax casting, back in the early 70's
I worked part time in a gunsmith's shop and we were talking about squirrels and how they chew through hard nut shells so easily, especially walnuts. One of the guys said he had some walnuts no squirrel could chew through. He left and a few minutes came back and put three walnuts on the table.
Nothing spectacular until we picked them up and realized from their weight that they were steel. They were perfect imitations down to the finest details. He had a good laugh on us, that's for sure.
Regards, Dave
TANSTAAFL: Your description brought to mind the first time I saw a wax casting, back in the early 70's
I worked part time in a gunsmith's shop and we were talking about squirrels and how they chew through hard nut shells so easily, especially walnuts. One of the guys said he had some walnuts no squirrel could chew through. He left and a few minutes came back and put three walnuts on the table.
Nothing spectacular until we picked them up and realized from their weight that they were steel. They were perfect imitations down to the finest details. He had a good laugh on us, that's for sure.
Regards, Dave
I've got history on the other side from TANSTAAFL (Good 'ol Robert Heinlein).
I worked for two years in a foundry that used sand casting. We had wood models of the parts, and to make a mould the sand was packed into a two-piece frame (basically, two steel hoop collars). The collars were seperated carefully and the master pattern(s) removed. The mould was reassembled and clamped, and the metal poured in. Once cooled, the haves were split and everything tossed into a drum where the sand was pulverized back to loose material in a wheelabrator machine and reused indefinately. The frames were reused. A one-off part could even be made using the oiginal part. Our patterns were a little fancier, as they seperated to allow internal features to be molded, sometimes using a seperately formed sand core (or several).
It is cheaper, because everything is reuseable and you only have to store a single pattern, not a large mould.
I worked for two years in a foundry that used sand casting. We had wood models of the parts, and to make a mould the sand was packed into a two-piece frame (basically, two steel hoop collars). The collars were seperated carefully and the master pattern(s) removed. The mould was reassembled and clamped, and the metal poured in. Once cooled, the haves were split and everything tossed into a drum where the sand was pulverized back to loose material in a wheelabrator machine and reused indefinately. The frames were reused. A one-off part could even be made using the oiginal part. Our patterns were a little fancier, as they seperated to allow internal features to be molded, sometimes using a seperately formed sand core (or several).
It is cheaper, because everything is reuseable and you only have to store a single pattern, not a large mould.
When doing mill wright work back in the 60's worked on turn arounds at some of the large foundrys. I recall seeing the sand molds of which you speak, man they could do some very fast pouring of that gray iron. If memory serves the sand was oiled and tamped in hard, even the sand was then reused.
I also remember they were casting small cast iron parts using some kind of a resin/sand mold mix, sand was tumbled coated with a resin, tamped into the mold, models were removed, and the molds were then run through a conveyor type furnace to cure the resin. The resulting castings were of a very good quality, looked almost the same as wax castings.
I also remember they were casting small cast iron parts using some kind of a resin/sand mold mix, sand was tumbled coated with a resin, tamped into the mold, models were removed, and the molds were then run through a conveyor type furnace to cure the resin. The resulting castings were of a very good quality, looked almost the same as wax castings.
Ya this was back in the late hippie days 70 to 75 , I watched some kids make crosses ect this way if I remember right even the small stuff was left out in the 105 Texas sun for 3 or 4 days , it took me 2 trys to get a triggerguard and that could of been 100 percent luck I wouldnt claim different just that it worked for me. :front: :front:
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