This is a Pressing Subject
When I tried spinning stainless steel, all I accomplished was making scrap, even after being annealed. Having already made the form for the spinning process, I decided to make a female die and use a press. The first combustion chamber I made was for Thomas Kamps design, so the small holes were for pins to hold the dies in alignment and also hold the material centered during the pressing. Two holes are for two of the hooked tubes, the other two for separating the dies after pressing.
The stainless sheet was cut to allow about 1/8 inch excess material around the lip after pressing. Before removing the sheet from the dies, I scribed a line (on the stainless) around the female die to use as a trimming guide.
Female Die Combustor Front
After getting plans for a combustion chamber with the injectors at the rear, I needed some way to hold the dies centered. A stepped dowel pin was machined for this purpose. The center hole in the female die is ¼ inch smaller than the OD of the inter chamber tube. When pressed the excess on the outer lip will crinkle up, but this material is trimmed away, and the rest of the lip will be smooth. The inter lip will split, but as the tube is spot welded on the out side, this should not be a problem.
Ignore the threaded end. It was used on another project and I just didn't take time to saw it off. A hole is cut in the stainless steel blank the same size as the small end of the dowel. This will keep the material centered. The larger end will center the male die while pressing, which is done in one step. Lay the female die on the press. Put a blank on the die and insert the small end of the dowel. Place male die on top and press.
Shouldn't have to mention this, but don't forget to make the female die big enough to allow for the thickness of the material you are using. I pressed .020 stainless steel shim stock, which is very hard, and it comes out perfect.
Now for the stick end. Because this has flanges in opposite directions, you will have to turn a different female die. The OD is the same. You will have to calculate the next step too fit the NGV that you will be using.
The OD of this step will be the OD of the NGV, plus 2 times thickness of your material. The ID of the hole in the center, is the OD of this step minus 2 times the length of the flange. A large washer is machined to fit over the dowel to form this flange. The dowel is cut to fit in this hole, with a step to fit the ID of the male die. I know this a bit confusing, but should become clear when you assemble for pressing.
Female Die Combustor Rear
Dowel with Washer
This picture is deceiving because the washer is a separate part form the dowel. A blank is cut with a center hole to fit this dowel. The male is pressed first then removed. Put on the large washer and press again to form the flange for the NGV.
I will be glad to answer any questions.