Finishing The Exhaust Manifold Form Block

 The glue is dry the clamps are off.

Part of my plan is to stretch the steel sheet into the opening in the block.  I don't believe I can stretch the steel enough to create all the shape needed.  To help that I want the edges of the sheet to slide a little between the block and the clamp board.  To let the steel slide and to allow the use of some grease, if needed, I've waxed the areas of the block where the blank will touch the wood.  I used 3 coats of Carnuba (paste) wax.  Particle board does not handle liquids well.  The compressed fibers swell up it they get wet.  The wax protects the wood from the oil in the grease if I need it to help the metal slide.

 To form the steel you need a piece of wood to clamp the steel so it doesn't just wrinkle up as you pound on it.  For this I'm using a piece of 3/4" plywood.  The shape of the cutout doesn't have to as precise as the form block.  I've layed out the cutout from the form block with the template and the free hand drawn the edge of where the bends will be formed.  You need room to get in to hammer on the steel and you need the clamping as close to the bend as possible.

 I made the clamp board in 2 pieces so I could have part of it tight and part loose as I form the shell.

 Based on how much I think the metal will stretch or slide I made up a template for the blank needed to make the shells.  The red line is the hole in the form block.

I punched 1/8" holes in the corners of the template so I can cleco it to a piece of steel while I scribe the cut line for the outside edge.

 For small parts I just clamp the boards together with the metal sandwiched between them.  I don't have enough clamps for something this big and I think it will be easier to work without the clamps being in the way.  Bolt holes were drilled in the form block on the drill press.  The clamp board was clamped in place and drilled through with a hand drill.
I also drilled a piece of plywood to put on the bottom so I don't accidentally break off the wood between the pipes.

Here is how the blank is installed in the form.  I clamp it with the bottom first so I can see how it is aligned then add the top half of the clamp board.

My first effort will be to experiment with just a small section of the shell to develop the tools without wasting a lot of steel.

I'm ready to start hammering steel.