Once you try it out, it's amazing how quick and easy it is to get the gorget on and off. This is James Bond technology for the 16th century!
Step 1: Create the Template
Before you start cutting steel, you want to do all your fitting with something much easier and cheaper to work with. I've found that manila folders are the perfect size and stiffness for creating templates for small pieces of armor, and they're sold in nearly every Walmart or Officemax. The cardstock of the manila folder bends nicely for decent fitting but they're tough enough to withstand repeated cuttings, foldings, and sizings.
Using a piece of string or cloth measuring tape if you're fancy, measure the size of your neck at the base (i.e. the collar). Then lay that down on the cardstock and create a circle.
Then measure at least 3 inches on either side, about 5 inches in front and 4 inches in back. I measured mine to be about 2.5 inches (the width of my belt leather) but that was too narrow, it should be closer to 3 or 3.5 inches to evenly spread out the weight of your armor across your shoulders (remember your breast plate and back plate are both going to hang from these shoulder pieces).
Then add 1/2" on all sides to account for the edge rollings you will need to do in later stages.
Verify it fits your neck and covers the top of your chest and the top couple of vertibrae in the back.
Cut the front from the back, then trace it again on another piece of cardstock, this time adding the details for the wrap over side and the hinge (if you want to create you're own hinge...I chickened out and used a store bought hinge instead of making my own).
Step 2: Cut the Steel
Trace the templates on the steel plate. I mark each piece so I can keep track of which is which while I'm working.
Using a beverly shear, or other steel cutting tool, cut the form out. Be sure to de-burr the edges with a grinder, sandpaper, or file, otherwise you'll soon shred your gloves while working the piece (and slice your neck while fitting).
Step 3: Shape the Front and Back
You want to start with the center groove or trough because that's harder to work after you've curled the shoulder sections. Using a sand bag or swage, hammer down the center of the front piece to form a shallow trough. The reverse side of this trough will raise the surface of the armor plate off the breast bone, protecting you from serious (i.e. deadly) injury if you're struck in the chest during combat. Make the trough about twice as wide as your spine, about 3-4 inches across, so as to allow the possibility that the plate may slide around during action. You really don't want the plate resting against any bone at any time, because Murphy's Law dictates that the one time it rests over a bone, someone will swat that plate in the worst possible spot.
Flip over the piece and hammer a shallow dish on either side of the trough, concaving in the opposite direction of the trough. This will press against the pectoral muscles further raising the plate off the breast bone and collar bones and taking advantage of the natural cushion of the muscle tissue. If you look at the plate from the bottom, the edge will have a shallow S shape.
On the back plate, hammer out a deep trough down the middle as well as a wide bowl around the collar. The reverse side of these will protect your vertebra and collar bone from injury. Check out modern day motorcycle crash jackets and see a resemblance.
Like the front piece, flip the piece over and hammer a shallow dish on either side of the trough, concaving in the opposite direction of the trough, further raising the plate off the spine.
Planish each piece to smooth it out. Hammer harden the entire piece to give it the stiffness it needs to stop blows from getting through. Planishing and hammer hardening was tricky because it tended to over exaggerate the curves I was trying to achieve. I was able to get it the way I wanted, but the next time I would save time and go with 410 stainless steel then harden+temper it in a kiln or forge.
Finally, curl the top shoulder sections into a semi circle. You want it to curl in two directions, straight over to make a C shape, but also concave a little to conform to the shape of your shoulder muscle. I bent the C shape by hand over my thigh, then used the english wheel and pneumatic planishing hammer to create the slight concave and harden the piece.
Step 4: Curl the Edges of the Front and Back Piece
Do not skip this step. If the upright collar section (which we'll make next) breaks loose during combat or other action, the edge of the front and back piece will be right up against your throat...you want the edges of the collar as blunt and safe as possible. After you've finished the curls, be sure the bowl shape is maintained, you still need to keep the edges off your bones and larynx. A few swats with the planishing hammer or poly hammer is usually all that's needed to knock it back into shape.
Step 5: Add the Hardware
It's hard to describe how this articulation works, study the pictures (especially the last one above) to get an idea of what it should look like when you're done. We permanently attach a hinge on one side, but that hinge needs to rotate on one side so the whole piece can be opened up and wrapped around your neck and shoulders when you put it on and take it off. It is held in place by hooking a hole in the front plate over a post on the back plate.
First we'll attach the hinge. Attach the hinge to the one side. The side of the hinge that attached to the front plate needs to be attached with two rivets and does not move. The other side of the hinge (the long side) will attach to the back plate with one rivet loosely connected so it can rotate on the plate. Use a washer in between the plate and the hinge so the rotation is smooth.
Attaching the rivets was tricky because the holes predrilled in the store bought hinge were made for wood screws, not rivets so the holes were way too big. Try to get a hinge without pre-drilled holes or make your own hinge if you have to.
On the other side of the gorget, attach a post. There are lots of ways to create a post, but I did an easy cheat. I drilled a hole and attached a machine screw and washer through the bottom of the plate and held it with a nut. Then I decorated it with an acorn nut on top. Then I ground away the screw threads until it was a nice post.
Punch the hole for the other side to fit over it's post. Don't drill the hole, use a whitney or other punching tool. I drilled mine and it caught in the drill and wrapped the whole piece around the bit, tore the hole and nearly ruined the whole piece. You can't see the tear from more than a foot away and it will be covered by the breastplate straps and pauldrons, but it will keep growing as the armor is used and eventually the piece will have to be repaired with a TIG welder or just replaced.
You can see in the pictures that there's a groove leading from the hole drilled for the post towards the back. You can cut a groove so the piece can slide along the post and lock in place, but I'm not sure how necessary it is. The way it's positioned the piece slides straight back when you get hit in the front throat, there's nothing to hold it place. The next piece I will try leaving out the groove entirely or think of some other attachment mechanism.
Step 6: Create the Lames
Lames are the vertical pieces that wrap around and protect the throat.
First create a cardstock template for the front an back lames. They should fit vertically inside your chest and back pieces. They should also be high enough to protect your neck from blows, but low enough to keep from breaking your jaw if you fall or get hit on the head from behind, or breaking the back of your head if you fall or get hit in the head from the front. Yes it's tricky and there are painful decisions you need to make about the tradeoffs.
Notice that in photo that I left tabs at the bottom of the pieces that can be folded perpendicular to the piece so it can be riveted to the front and back plates.
Shaping the collar is easy, just bend it over your thigh into a C shape, and just use your hands to shape it so it fits snugly in the front and back pieces.
Curl the tops and bottoms of both lames.
Finally, fold over the tabs so they fit against the front and back plates. You'll probably need to hammer them into a concave so they fit flush against the concave of the front/back plates.
Hammer hardening the lames was really tricky because the pneumatic planishing hammer I had access to only has a concave hammer and anvil, so planishing tended to warp and distort the shape I was trying to achieve. This is a situation where using 410 stainless steel then harden it in a forge or kiln would really pay off.
Step 7: Attach the Lames to the Plates
Now we rivet the lame to the plates through the tabs (the tabs are positioned underneath the plates). I took some tweaking to get the tabs to fit flush against the plate. I used 1/8" round head stainless steel rivets with washers on the bottom to give it some extra strength and prevent the rivets from popping when getting hit.
Step 8: Polish the Piece
I like a satin or brushed finish because it hides all the nicks and dings the piece gets while used, but you can polish it to a mirror finish if you like.
I used a wire wheel on a grinder but you can also use a wire brush attachment for an angle grinder.
Finally, seal it against the elements. It's stainless steel but it will still tarnish and discolor (i.e. stain). I'm thinking the name "rustless but not stainless steel" didn't sell well, so the marketing guys just shortened it to "stainless steel". I used Johnson Paste Wax, rubbed in with a paper towel the polished off with a lint free shop towel.
You're done! Have fun storming the castle!