First, lay out the patterns for the lower sections of the front and back pieces (see image right). Then cut and de-bur these parts.
Next, shape and form the front "chest" piece. To get the right shape, it helps to gently dish this part then bend each side down evenly to rest on the shoulders. Then form the "back" plate, again bending the sides down so the piece rests on the shoulders. Make sure the two plates overlap correctly. Once the plates are shaped, flare the inside "neck" line up to create a 3/8" lip (see image left). The lip provides a surface to rivet or weld the upper section, too.
Measure the lip (neck line) of the front and back plates. Use these measurements to pattern out two long, rectangular plates, each approx. 1½" to 2" in width (higher if you plan to roll the top edge). These plates form the neck guard or "collar" for the front and back pieces. Cut and de-bur these parts. Next, bend these plates to form a "C"-shape. Bend this C-shape to fit the neck line of the front and back plates (see image right). Bend the plates evenly, being careful to ensure a close fit with the lip of the lower parts.
Using clamps (Vise-Grips) attach the top "collar" plate to the lower chest plate. Drill a series of holes approx. 1 inch apart. To assist in fitting and holding the two pieces together, use small bolts in the holes (see image left). Drilling the holes in an alternating pattern and bolting together as you go will help to draw the two plates together evenly and insure a better fit. Repeat this step for the back piece.
If required, roll the upper edge of the "collar" piece on both the front and back pieces. You can also flare this edge instead of a roll, however, this edge must be finished for safety due to its close contact with the throat and neck.
Sand and polish the pieces to the desired finish. I recommend a simple "brush" finish using a wire-wheel. Using a paste-type metal polish with a brass wire-wheel can produce a nice "munitions finish".