The blocks used for doming and swaging are used to form metals into half-spheres and half-cylinders. The blocks, which are made from steel or brass, are available in a range of sizes, and they are used with wooden punches that match the shapes of the blocks.
Cut the metal to be shaped to the appropriate size and anneal it. For example, if you want to form a dome of about 5/8
inch in diameter, cut a circle with a diameter of 3/4 inch and place it into the hollow of a dome that has a diameter of 7/8 inch. Find a punch that fits the hollow, but remember to allow for the thickness of the metal being shaped.
Once the dome has been shaped, you can bring up the outside edge of the dome so that it will form a neat half-sphere. Punch the dome through a hole drilled in a steel sheet.
The entrance side of the hole should be countersunk, and the punch should be able to pass right through the hole, allowing for the extra thickness of the metal dome.
There will be times when you cannot match the punch to the dome. You may, for example, want to make a large domed piece by forming it in a sandbag or on a lead block, or you may have a doming block but only a limited selection of punches. To overcome this problem, place the circle of metal in the block, on the sandbag, or on the lead cake, position the punch over it, and strike the punch, working first around the outside edge of the metal to begin the shaping process, then gradually working down into the center in a series of ever-decreasing circles.
When you use lead cake to shape metal place a piece of cloth or soft leather between the lead and the metal. Any particles of lead that are left on metal during heating melt very quickly and burn holes in the metal, with potentially disastrous results.
When you need to cut out several circles to the same size, it is tedious to do them all by hand. You can either make a tool to do the job for you, or you can buy a tool with a series of different-size holes and matching cutting punches.
A swage block is used in exactly the same way as a doming block, but this time you will need to use the handles of your punches, laid on their sides, to shape the metal into the hollows of the block. Use a wooden mallet to strike the handles so that they are not marked, or place a flat plate on top for protection.
If your punches do not have handles of the correct size, use a small metal rod to push the edge of the metal into the curve, and gradually work the rod into the center. Work gently, hitting and pushing, and decrease the size of the rod to prevent "creasing."
Writer – Jinks McGrath