Traditionally, metal spinners prefer to drill and tap a hole in the form. One advantage to this method is avoiding misalignments from using the scroll chuck. The 2nd advantage is not placing and replacing the faceplate from form to form. Drilling and tapping is less expensive in the long run and your forms will not suffer from misalignment. Turn the wooden blank in your lathe to the shape you desire for the form. REMEMBER, if your form is not ever expanding (continuously opening), your spun piece will be locked on the form. It cannot be removed without either cutting the metal or cutting the form. I have seen pieces intentionally locked on the form. An example of this would be something like a lamp base where the extra weight of the wood is needed to stabilize the lamp.
Follow Blocks
Make a follow block of hard wood that matches the size and shape of the base of the form. You may use a live center with a 60 degree point if you cut a matching cone in the back of the follow block. A handy way to cut a cone in a follow block is to use a 60 degree center drill available from a machine tool supplier or Harbor Freight. An easier to use follow block can be made using a live center that has replaceable points. In your lathe, turn a shank that will fit your live center hole using hard wood. Reverse the follow block and turn the face of the block to match the base of the form. Fit this follow block turning into the live center body and you are ready to go.
Back Sticks
Use the back stick to help iron out wrinkles in the metal, support the back of the metal disk while spinning and to support the disk while applying lubrication. The back stick is made of any hard wood. Use a short back stick with small diameter spinning and a longer back stick with bigger projects. Dimensions of the back stick are not critical. A stick of hard wood approximately ž" thick by 2" wide by 18" long is a handy size. Taper the business end of the stick back about an inch on each side or more as it suits you.
Trim Tool
Using the trim tool is one of the more dangerous operations in metal spinning. If this tool is not used correctly, you will ruin your work and you may require urgent medical care. Use this tool only when it is properly supported on the rest and prevented from sliding by a fulcrum pin. Do not over reach, move the rest closer. Trim the edge only at the point the spinning is almost completed. Use a firm grip. If your spinning is very out of round, dismount the work and trim it with tin snips. A heavy scraper with a square edge can be used to trim.
Annealing, in metallurgy is a heat treatment wherein the microstructure of a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces equilibrium conditions by heating and maintaining at a suitable temperature, and then cooling. It is used to induce softness, relieve internal stresses, refine the structure, and improve cold working properties.
Pewter and pure aluminum (1100 – O) do not easily work harden and will very rarely need to be annealed. Copper and brass will work harden and need to be annealed.
To anneal copper and brass, place the disk on a fire proof support that will not draw heat away from the metal. Use steel rods set on end to form a support on which the disk will be heated or use a short section of large diameter steel pipe set on a fire proof platform. Do not heat metal on a concrete floor. Heat the metal with a propane torch in a darkened work area. When the metal turns just a dull red, maintain the dull red color for 20 or 30 seconds, then remove the flame. As quickly as conveniently possible, drop the heated metal disk into a metal bucket filled with cold water. In a few seconds the metal may be removed, dried off and go back on the form. Be very careful in this process not to burn yourself or burn your shop down. Have a fire extinguisher handy and do your annealing well away from flamable materials. If you are using aluminum alloy such as 3003 H14 you must anneal it prior to forming. Heat the aluminum until it will just char the end of a pine stick and quench it immediately in cold water. You may have to re-anneal it several times to get it down to the form. Small disks can be annealed with a small torch. Hold the metal disk at the edge with pliers. Do not use your good pliers for this operation.
Pickling
Pickling is the immersion of metals in an acid solution for the purpose of removing surface fire scale and oxides caused by heating, annealing, casting, soldering etc. This is a dangerous operation. I prefer to simply use very fine sand paper to remove the scale. The metal can still be polished using buffing compound.
Polishing
If your metal is rough, try a medium grit sand paper. Work towards finer and finer grits until the surface is uniform. Steel wool works well also. Both sand paper and steel wool will leave a brushed surface. For a polished surface, use metal polishing compounds. Tripoli polishing compound in stick form is available and works well. Finer compounds are also available for a higher shine.
From: http://www.t4lighting.com