Hi Folks,
Some of you might be interested in how I cast a pair of gun case hooks using the Delft clay casting method. The process is the same as sand casting but uses a fine clay to construct molds rather than sand. I am building a case for my dueling pistols and needed hooks of a style used in the 1780-90's on English cases. Peter Dyson (in England) sells them but I wanted to make hooks of my own design. The Delft clay process worked perfectly for my needs.
The first step is to make the model of the hook. I carved mine from hard green carving wax supplied by Rio Grande Inc.
Simple tool are needed such as course files and carving knives. I drew a pattern on paper and then copied it twice on my printer. One of the copies was printed as a mirror image because hooks were generally installed as mirrored pairs.
Once the hooks were carved and smoothed (using knives and a burnisher)I prepared the mold for the first casting.
The mold building requires the casting frame (made or supplied with the Delft casting kit), the clay, a straight edge for cleaning up the mold, a hammer for pounding the clay, and some awls for making the sprue holes and gas ports. You push some clay into the bottom half of the casting frame and pound it flat with the hammer. Clean off the excess with the straight edge and then gently push the wax model into the clay.
Then you dust it with some talcum powder and brush the powder over the model. Next place the upper half of the frame on the mold, carefully lining up the index notch.
Next fill the upper half with clay and pound it in.
Clean up the clay as before and carefully open the mold.
Gently remove the wax model and use an awl to cut a series of gas vents into the upper half of the mold. Push the awl through the clay to the surface to create holes for escaping gas. Gas buildup can create back pressure that inhibits the flow of the molten metal.
The next step is to cut the hole for the entry of the metal (sprue hole). The hole is shaped into a funnel using a carving knife. It connects to the back side of the hook mid way up the shank.
Now you are ready for pouring. I used scrap brass that I cleaned with a dip in muriatic acid. I heated the metal with a high intensity torch using mapp gas. You can used a gas welder (I do for bigger pieces requiring a lot of metal)burn out oven, or forge.
The molten metal is sprinkled with borax flux and the dross (scum) is removed with a graphite stirring rod. Finally, when well heated and liquid, I pour the metal into the funnel of the mold.
The mold is left to cool and then opend to remove the hook.
The thin layer of burnt clay is scraped away and the rest is put returned to my clay supply for reuse.
The sprue is cut off and the hook filed and sanded.
Here is the finished hook installed on the case. The Phillip's head screw will be filed off and shaped into a rounded stud when permanently installed.
I am using a stud to anchor the hook although most hooks of this style were anchored with eye screws, not studs. I just don't like the appearance of the eye screws. Finally, here is my treasure trove of wax models I have made and cast for other guns and jewelry.
The Delft system works well for small projects up to small to medium sized side plates. Obviously, it is only used for nonferous metals. It is not expensive when used on a small scale. The casting kit cost about $80 and can be used for a lot of castings. You need the heat source and borax and the means to make models. Models can be wood, metal, wax, plastic etc, or you can copy an existing piece. Anyway I hope you found this interesting and useful,
dave
