This post was originally created as a PDF guide by Legio XIs Alex Matras. It is one of the most comprehensive and understandable segmentata tutorials around. The PDF can be downloaded in the link provided below. Otherwise, you can read the whole thing here.
Construction of a Lorica Segmentata Legio XI CPF
This guide is intended to supplement existing patterns and advice for first-timers constructing their own lorica segmentata. I do assume the reader has some basic experience in the shop and with shop safety, and provide this guide with the intent to encourage reenactors to construct their own segs. My hope is that this guide can keep the prospect of constructing one from seeming too daunting or overwhelming. It can be done with only a little skill (that comes with some practice) and some patience more than anything else. Much gratitude goes out to Matt Lukes for answering many of my questions and for his superb advice and assistance Matt Amt for providing patterns and advice on the Legio XX website and to. I am not an expert in armor construction and this guide is simply a compilation of the tips and advice I've received from others, from various websites and some things I figured out for myself. Enjoy!
Recommended Tools & Materials
Patterns & Sizing
Cutting and finishing metal plates
Folding & Flaring
Assembly and Riveting
Recommended Materials Metal Working Tools
Right angle straight edge
Center punch (for marking hole positions)
Step bit (fits into socket for removable bit screwdriver)
Armoring raising hammer (my favorite hammer!)
Ball peen hammer
Edge deburring tool
Selection of metal files
15 lb anvil
1/8” rivet set (optional)
3/16” rivet set (optional)
Throatless metal shear (or pneumatic metal shears, not pictured)
Dremel rotary tool with the following bits:
Not pictured: -Vice grip (as large of one as you can get your hands on) -Drill press (not vital, but will make this project considerably easier)-50-70 lb anvil (nice to have but not necessary)-Metal yardstick-Deep-throat metal punch (only if you don't have access to a drill press)
Pictured to the left are some optional hammers you may consider, especially if you plan on working with 16 ga metal (though details of working with 16 ga are not discussed in detail in this guide).-Rubber mallet (good for straightening bent pieces)-Teardrop shape plastic mallet -2-3 lb. rounded face sledge hammer-“Swedish style” cross peen hammer
Leather working tools
Leather strap cutter
Edge beveler (optional)
Nylon edge smoothing tool (optional)
Leather punch (optional, if you don't have a drill press)
Raw materials 8-9 sq. ft. cold rolled sheet steel (all 18 ga., or partial amounts 16, 18 & 20 ga.)
5 oz. veg-tanned cowhide (approx. 2-3 sq. ft.) 8 oz. veg-tanned cowhide (< 1 sq. ft., scraps will suffice, for external straps)
200 1/8” copper, round head rivets
100 1/8” copper, flat head rivets
16 3/16” copper, round head rivets 0.020 sheet brass for fittings (if fittings are not purchased)
Other materials 100 & 220 grit sandpaper
green Scotch-Brite pads
200+ 5-40 1/4” long machine screws and nuts (optional, 4-40 will suffice)
Sources for tools As with every project, the correct tools make the job much easier. Many of the recommended tools are available at hardware stores, but many have to be purchased from catalogs or internet merchants. The armor raising hammer (6) is available at www.blacksmithsdepot.com (#219). This is the best hammer for working metal in my opinion since is has a broad, but curved face that leaves minimal marks. Also consider a heavier cross-peen style for working with thicker sheets. It is best not to use a standard claw style hammer for working metal. If you on a strict budget, a ball-peen would work better. The deburring tool (6) is available from McMaster Carr. Use this tool to smooth edges of cut sheet metal. The rivet sets (12, 13), while not essential, will make riveting easier and are available from the “in-stock” page at Clang Armory ( http://clang.adkinssoftware.com ). The step bit (3) is what I use for deburring holes. These are very cheap from Harbor Freight. While nothing is better than a good, high-quality anvil with a hardened, polished surface, the cast steel ones from Harbor Freight will get the job done. Coating the anvil face with leather will keep the rough surface from marring the work. If you order the sheet metal in strips, then you will only have to cut them down to length and cut the proper shapes out for the shoulder pieces. The Harbor Freight throatless metal sheer (14) works very well for this. Pneumatic hand shears will work as well, but scissor-style hand shears will not work. If you don't have easy access to a drill press, consider purchasing one. These are useful for drilling holes for rivets, fittings and even leather, and are much easier to use then a punch in my opinion. The leather working tools are available from Tandy ( www.tandyleatherfactory.com ). Odds are, someone in your legion has most of the tools you'll need, and if you are on a budget, you will probably be able to make do with fewer tools. Those selected are based on my personal experience of what makes the process the easiest.
Sources for materials My recommendation for the sheet metal is to purchase from a vendor who will cut the metal into strips for you. Many will do this for a nominal fee ( www.onlinemetals.com is one such vendor). Otherwise, sheet metal is best purchased from McMaster Carr ( www.mcmaster.com ). The rivets and the machine screws are also available from McMaster Carr. The machine screws are not necessary, but can be used to test for correct sizing and accurate drilling before plates are assembled. The best size for an 1/8” hole is 5-40 x ¼ inch, but this is a rare size to find at a hardware store, and 4-40 will work. The leather is available from Tandy. The 5 oz. is available in a single shoulder, and a small belt blank is your best bet for the 8 oz.
Assembly Overview Building a lorica segmentata may be one of the most challenging projects one can undertake in the reconstruction of legionary kit, however none of the steps are extremely difficult or require expert skills. Care, patience and some practice beforehand are required, however. The first (and perhaps most important) step is to construct a paper pattern, sized to fit the wearer. It may also help to take some very thin sheets of steel and construct a prototype for the pieces that fit around the neck. This helps establish the proper curvature and ensures the pattern is the correct shape (since paper does not bend like metal). The most tedious step is fabrication of the fittings. Since there are already fantastic tutorials on fittings, that will not be covered in this guide. Additionally, fittings can be purchased at reasonable prices from a couple different sources. Purchasing the fittings will very significantly reduce the amount of time required. The next step is to prepare, cut and deburr the metal. This involves cutting sheet steel into strips, rounding the corners, filing the edges and polishing. Some edges will need to be rolled under and some may be flared up. This is the step that requires the most skill, and you will probably need to practice on scrap pieces of steel before attempting this step on the real pieces. After this, the rivet locations can be mapped out and the holes carefully drilled. The next major step is to prepare the internal leather straps. This involves cutting the straps out of 5 oz. leather, determining the locations of the holes for the rivets (I give a fairly detailed set of steps to do this), drilling the holes and coating with neatsfoot oil. My method for laying out the holes in the straps requires the strips to be straight, so the bending is done after that step. Most of the pieces can be bent by hand, but depending on the thickness of the metal chosen, some hammering on an anvil may be needed for the thicker pieces (again, I recommend practicing this beforehand). After all pieces are bent into the proper shape, the fittings and straps can be riveted on, a final polish applied, the four sections buckled together, and finally and great sense of pride will consume you as you put it on for the first time. Some final thoughts before you get started: While this guide intends to be somewhat comprehensive, it is not a replacement for thought and planning on your part. So, please don't rely on this or any other guide or patterns to the letter or expect them to solve all problems which may arise. And remember that there are many people willing to help when you get stuck. Be sure to read the safety instructions for all of your tools and take all necessary safety precautions. This includes wearing eye and ear protection, keeping your fingers and hands away from cutting blades and any rotating machinery and using safety guards provided for some tools.
Patterns and Sizing Constructing the Patterns The best place to find a pattern for a lorica segmentata is the Legio XX website ( http://www.larp.com/legioxx/lorica.html ), where there are links to patterns for the Corbridge A & B cuirasses. These patterns may need to be scaled up before printing to ensure they are the proper size. The patterns will probably need adjustment, but these serve as a good starting point. A very important step is to make a pattern out of poster paper, making the necessary adjustments to fit the wearer well. A segmentata consists of several pieces:
Left and Right Girdle Plates- The right strips are 1.5 inches longer than the left so there is ¾ in. overlap where they meet in the front and in back.
Lesser Shoulder Guards- There are different options on how to do these. The instructions in this guide use the default layout of having two smaller and to long ones on each side. The smaller ones have a trapezoidal shape, with the upper pair being rectangular..
Upper shoulder Guards
Top Back Plates
Lower/Middle Back Plates (I think you should consider a slight deviation from the pattern so that the right ones should be ¾” longer to allow for overlap to match girdle plates)
Pattern adjustment There are a couple guidelines on how to adjust all the pieces. First, be wearing your tunic and subarmalis or at least something that will give the proper girth and shoulder padding. That ½” of padding in the shoulder makes a significant difference in the final fit. If you don't have a subarmalis, use a thick sock at a minimum to replicate the padding. Since this is such an important step, I would highly encourage you to get a friend to help and seek out advice from that who know this v The width of the girdle plates should be very close to 2¼ in. To get the length, measure the widest part of your torso. If you are in shape, it should be under your armpits and around your pectorals. Don't overestimate this. You can always loosen the top girdle plates a bit since there is some overlap. However, if you make them too big, you can't tighten them and your left arm will get numb when carrying a scutum (trust me on this one). If you have a gut, things are a little more difficult. Since you will need to breathe, the best thing is to get the circumference at the widest part around the belly. Just know that the upper girdle plates will probably be oversized. Half of the circumference will be the length of each left girdle plate. Add 1.5” to this to get the length of the right girdle plates. If you are shorter, you may need only 7 plates, but do not increase or decrease with width of the plates by much, rather use more or fewer plates. I believe that the segmentata should come to just below the navel. I am 68 in. tall and only needed 7 plates. Next, the breastplates, mid-collar plates and backplates can be adjusted. The breastplates and mid-collar plates are mostly adjustable in length, and the backplates should be adjusted in any dimension necessary. To get the front-to-back length you may want to try making the top girth hoops and measure the distance from about 1/4" below the top edge of the front, over your shoulder, to about 1/4" below the top edge of the back. That will be what the combined length of the breastplates, mid-collar plates and all 3 back plates must be. The back section (three plates combined) is about the same as the length of the breastplate, the remainder being the mid-collar. Using simple algebra you can solve for the lengths.The widths of these plates can vary slightly as well. Keep in mind that the breastplates should overlap each other at an angle. This will tend to push the mid-collar plates apart, leaving room for the neck. Don't be tempted to make the curve in the breastplates much more than they are in the pattern. The long end of the upper shoulder guards should be about the same as the breastplate and the center plate should be roughly the same length as the mid-collar plate. The lesser shoulder guards should not be adjusted. The dimensions are remarkably similar in the archaeological finds. But seriously, get some expert advice on this step. There are many folks on Roman Army Talk who would be willing to help.
I personally found it useful to make a prototype for the neck pieces out of thin 22 gauge sheet steel or aluminum. This is thin enough that I could bend by hand, and allowed me to capture the proper curvature of the plates. Paper just can't do this. This is completely optional, but the benefit is when you are ready to bend the breastplate and mid-collar plates, you will have something to compare them to while hammering them out to the proper curvature. A picture of the metal prototypes I made for myself is to the left. Fittings If you choose to make your own fittings, it will at least double the time it will take. I purchased my fittings from Keltica ( www.kelticaironagevillage.com ). They sell an excellent set for the Corbridge A, all you will need to do is polish and enlarge the holes. Fittings may be available from other sources such as Matt Lukes, and rivet bosses can be purchased from Clang Armory. If you choose to make your own, please consult the guides on the Legio XX website ( http://www.larp.com/legioxx/lorica.html ) or Jared Fleury's website ( http://www.florentius.com/buckle.htm ) for buckles.
Cutting & Finishing of Metal Plates The first major part of construction is to cut the metal parts, give them a simple polishing and finish the edges and corners.
Which thickness to use? It is common and acceptable to many groups to use 18 gauge (0.048 in) for all plates, but actual finds indicate that the thickness varied. Matt Lukes recommends on RAT to use 16 gauge sheet steel for the breastplates, mid-collar plates and top back plates & upper shoulder guards, 18 ga sheet steel for the remaining shoulder pieces, and 20 gauge for the girdle plates. Using 16 gauge presents some additional challenges, because it is more difficult to work.
Thoughts on pre-cut metal By far, the easiest way to cut the sheet metal for the girdle plates is to use a large industrial sheet metal shear. Very few people happen to have one in their backyard, so a good alternative is to just order the metal pre-cut into strips. Many suppliers will cut the sheet metal into strips for a nominal fee. I recommend at least having the girdle strips pre-cut since they are the most difficult to cut by hand, and optionally have strips cut for other pieces that you can cut further into the shapes needed for the shoulder plates. Be sure to get extra strips as you are bound to mess something up your first time and will need to redo a piece.
Cutting strips and plates Before any cuts are made, you should score all the cut lines with an awl and a straight-edge (or by tracing the pattern directly onto the metal with an awl). Hand shears can not handle 16-18 ga steel, so a throatless metal shear is recommended for most cuts (esp. curved shapes). The actual Beverly shear costs well over $500, but one is available for under $150 from Harbor Freight. These are very easy to use, so long as you cut slowly and carefully. When tracing patterns that will have rolled or flared edges, don't forget to leave an extra ¼ inch. Another tip is to cut slightly outside the line and finish using a belt sander. Pneumatic hand-shears are a good option for long, straight cuts, but beware that you will lose a 3/16” strip for each cut, so adjust your layout accordingly.
Finishing the metal After a plate is cut, snip off about 3/8” of the exposed corners and use a Dremel with a carbide grinding bit to round them off. Rough edges can also be evened out with this same bit or by using a belt sander. Deburring is very important to keep from cutting yourself with sharp edges and can be done with a hand deburring tool or with a Dremel. A satin finish is most appropriate and can be achieved by scrubbing back and forth along a plate's length using green Scotch-Brite pads. The texture of sheet metal will have many tiny pores that give it this satin finish. If the metal is in superb condition, it may only need to be polished with steel wool to restore the finish. Over-sanding will polish out these pores and will yield more of a mirror-finish. Do not store your pieces outside, or you will notice rust will quickly ruin your polish.
Painting You may wish to blacken the insides of the plates. This could be done by heating over a forge and polishing the top afterwards. Although it is not authentic, you could also spray paint the backs of the plates to make it easier to prevent rust. If you do not paint the inside, don't forget to keep it oiled.
Folding and Flaring Edges This step requires the most skill and should be practiced thoroughly on scrap beforehand. First, the bottom edge of the lowest girdle plate and a potion of the top edge of the top-most girdle plate must be folded under. The bottom girdle plates are also slightly flared as well. If you are using 18 ga for all shoulder pieces, you may either fold or flare the edges around the neck (but don't do both). Flaring is turning the edge up at 90 degrees and sanding the edge smooth. Although it requires fewer steps than folding the edge under, it requires more care to avoid scratches and marks on the flare. If you are using 16 ga for the pieces around the neck, then flaring is a better option than folding the edge under.
Folding and flaring the girdle plate edges The easiest step here is to begin folding the edges for the bottom girdle plates. Start with the bottommost girdle plates. Scribe a line all the way across on both the left and right plates, 1/4” from the bottom. Line the jaws of a vice grip with thin cowhide and secure one end of the strip in the jaws, with only 1/4” sticking out (the scribe should be aligned with the top edge of the vice, see picture below). Begin by lightly hammering the top of the plated horizontally toward the direction that will be the inside of the plate. I find that my armor raising hammer works best here, however a simple ball peen may suffice. Work your way across the clamped section. Do not try to bend the metal too much at once, about a 15 degree bend is sufficient for the first pass, but do keep a smooth, flat surface and lightly tap any bumps to flatten them out. After the section clamped in the vice is bent, then unclamp and slide the piece over, and re-clamp the next section. After the first pass all the way across the plate is complete, then start going the other direction, bending about another 45 degrees. Use a third pass all the way across again to bend the work to a full 90 degrees. After this, line an anvil with cowhide, and place the work on the leather. Strike the edge to bend the work the rest of the way over, again using multiple passes to keep any bends from being too severe (as this will cause warping that is difficult to smooth out). Finally, hammer the folded edge completely flat. Now, the edge needs to be flared out. This means securing in the vice grip again, only this time hammering the other direction to achieve about a 30 degree bend outward all the way across. The top girdle plates have about an 8” section, under the arm pits that are folded in the same manner, but not flared outward. These steps are pictured below.
1. Starting the first pass. Bend only about 15 deg.
2. First pass is complete. Starting the second pass
3. The third pass is complete
4. Starting the fourth pass on the anvil
5. The finished fold on the top girdle plate
Folding the edges of the pieces around the neck You can use the same technique for the neck pieces as the girdle plates, except only a small section can be hammered over at a time, and constant readjustment is required to accommodate the curved edge. It is also likely that the entire shoulder piece will not fit into the vise. In this case, start hammering as much of the edge as you can in the vise, and finish the rest on an anvil. It isn't too hard with 18 ga or less. The alternative to this is to flare the edges outward.
Flaring the edges of the pieces around the neck Although flaring actually requires fewer steps than folding an edge under, it is actually more difficult because extra care must be taken to ensure that the edge remains neat, and that no vice, anvil or hammer marks scar the flare. This wasn't a big deal when the piece was folded under, but now any mistakes can be easily seen. Essentially, just repeat the same steps as before, but hammer the edge in the other direction so it is bent outward. Again, do as much as you can with the vice, and when you get to the point there the plate is too wide, lay in on top of a small anvil, with the flare pointing downward. Hammer the plate edge toward the side of the anvil, constantly readjusting the plate position as necessary. Be careful to ensure that you keep the anvil lined with leather and it also helps to use a file to round off the anvil edge to smooth it out a little bit. If you are doing this step with 16 ga. steel, you will need to use a heavier hammer and will essentially need to beat the snot out of the edge to get it to bend over all the way. This will require much practice beforehand to master. After you are done, use a file and sandpaper to get the flared edge as smooth as possible, as this will be in contact with your skin quite often. Flaring the breastplate edge (using 2 lb. hammer) Finished breastplate flare
Drilling Drilling is a fairly easy operation, and if you follow a few tricks, you will be able to drill the holes quickly and accurately. There are two types of holes to be drilled into the pieces: holes for fittings and those for straps. It is very important at this step to begin labeling your pieces (especially the fittings), because it is likely that the hole locations will not be interchangeable.
Marking holes for leather straps You should measure and mark the locations for all the strap holes in a piece before you begin drilling. These can be measured and drilled at this point for the girdle plates and most of the holes for the straps on the neck plates, but it will be best to wait for the some of them on the neck pieces until you are laying out the leather straps (it can be difficult to predict where to drill beforehand). My approach is to measure and find the center point of each strip and mark it on the back side. Then, measure the location of each hole from the center point. Once you have one plate, you can use it as a template for the others. For the girdle plates, you need three sets of two holes, each 1.5” apart. The first set is in the center, and the other two are on each end. Measure each hole location from the center point and scratch a vertical mark with an awl. Measure about 1/8” from the upper edge and mark a horizontal line with the awl. Where the two marks intersect is the center of the hole; use a center punch to mark this position. For the lesser shoulder guards, there are three holes, with the distance between them growing by about 3/4” for each piece toward the shoulders. Do not worry about marking the locations for the strap rivets in the upper shoulder guards, mid-collar plates or breastplates at this time.
Drilling holes This is best done on a drill press to ensure a straight hole, centered exactly where you want. Use a 1/8” drill bit, and let as little of the bit protrude out as possible. Place the metal on top of a piece of scrap wood at least 3/4” thick. Lower the drill down and ensure that it will fall very close to the point that was punched earlier. If you punched it deep enough, the drill will “find” the location you punched and drill exactly where you intended. Hold the metal securely and turn the drill on and lower it until it just drills all the way through. After drilling all the holes, use a deburring tool (or a step drill bit) to deburr the hole and ensure a rivet fits through. Use care when using a drill press, and ensure that what you are drilling is well secured. This is to help prevent injury to yourself and to keep parts from getting caught in the bit and spinning around.
Drilling holes for fittings It is not necessary to mark the fitting holes, rather just trace the location of the fitting on the front side of the metal plate with a pencil. Place the plate on the wood block just as before, but now place the fitting on top in the proper location, and drill through one hole. Place a flat head rivet through the hole from the bottom to secure the fitting's position and drill the next hole. Place another rivet through this hole and continue until all holes have been drilled. Use a new fitting for the next set of holes—they will not be interchangeable. You must label the fittings with the exact piece and location to ensure they don't get confused. A fitting will most certainly not fit through holes drilled for another fitting. Also, be sure you drill the hinge fittings on the breastplates, back plates and front/back upper shoulder guards so the hinge is 1/4” in from the top edge to allow for the center plates to overlap these pieces. Also for the neck pieces, be sure to account for the overlap in the flare if you choose that option. It is best to line these pieces up together to ensure they overlap properly before marking the fitting location. You will need to use a 3/16” bit for the 4 internal buckles on the back sides of the left and right top girdle plates and don't forget that there are no lacing loops on the bottom girdle plates (so don't mistakenly drill holes for those). I hope you ordered extra strips for the girdle plates just in case...
1 A careful observer will note that in the picture, I am installing the fitting on the back of the plate, and not the front. That piece was a sample only for this guide, and this was an error on my part. Do not repeat this error yourself.
One final note on drill presses: spindle speed does matter. If your holes aren't coming out very neat, you may want to adjust your speed. Even cheap drill presses have adjustable speeds (by moving the drive belt to a different configuration). Consult your users manual for the proper speed and belt adjustments for the drill bit size and material type you are using. Small drill bits going into brass tend to use the highest speed and large drill bits in steel user lower speeds.
Leathering Cutting the leather straps is probably the easiest part of the process, and determining the locations of the holes isn't too difficult either. Several straps need to be cut: 6 for the girdle plates, 6 for the shoulder plate straps, 4 for the back plate straps and 4 for the exterior buckles. 5 oz. leather is used for the internal straps, and 8 oz. should be used for the exterior belts. After the straps are cut and drilled, they should be coated with several coats of neatsfoot oil.
Marking Hole Locations in Girdle Plate Straps Cut 6 straps 1.5” wide and 15” long out of 5 oz. leather using a strap cutter or X-acto knife and straight edge. Clean a large work area on a table. Place the bottom girdle plate, top side up along the bottom edge of the table. Use the right-angle ruler and line each leather strap up exactly perpendicular to the plate, with about 1/4” of the straps underneath the girdle plate. Tape the plate and straps down very securely to the table so they can not shift. Line some tape 1/4” (or just slightly more) below the top edge of the girdle plate. Use a 1/8” drill bit and turn by hand through the holes in the metal to mark the position where the holes in the leather straps are to be drilled. Place the next plate so that the bottom lines up with the tape. Use the right angle measure to ensure it is parallel to the bottom plate and aligned on the left side. Tape this piece securely to the table, and mark the positions of the holes. Repeat this process for each piece up to the top-most girdle plate. After you have marked the top holes, draw a line along the top of the plate to indicate where to cut the strap so it does not stick above the plate. Repeat the entire process for the right girdle plates.
Marking Hole Locations in Shoulder Plate Straps Cut 4 straps 1/2” wide and 10” long and two strips ½ x 14” out of 5 oz. leather. Follow the same process as the girdle plate straps. The straps on each end will be at an angle, however, and you may need to layout all the pieces to figure out the angle first before taping the straps down. You will also be able to determine the location of the strap hole in the breast plate, mid-collar plate and in the upper shoulder guards. Be sure to mark the location with a center punch and drill. I recommend placing the upper shoulder guards on last since they overlap the lesser guards and neck pieces. After you layout the lesser guards, measure 2 inches and layout the neck pieces, using the machine screws to hold the pieces together with the hinges. There is no strap hole in the top back plate, the strap will be fastened in hole used for the internal back plate straps. This is all illustrated below. After the hole locations are marked, mark the end of the straps. Marking the shoulder plate strap holes, just before the upper shoulder guards are placed on top.
Drilling & Cutting I recommend using the drill press to drill the holes. As with drilling the holes in metal, place the leather on a piece of wood and drill through. You may need to take an awl and stretch the hole and ensure an rivet can fit through. After drilling, use an X-acto knife to cut the strips to the needed length. To cut the external straps, use four ¾ x 5 inch strips of 8 oz. leather and cut one end of each to a triangular tip. Do not drill holes for the buckle just yet, that will come when you start assembling everything together. You can attach the fittings to the square end by inserting the leather between the the brass tabs and drilling through. Coat everything with several coats of neatsfoot oil to soften it up. The shoulder straps need to be especially flexible for the lesser shoulder guards to hang correctly.
Using a hammer to bend the flared edge on the breastplate Bending Girdle Plates These are easiest to bend because it can be done by hand. I recommend taking some scrap strips, cutting them to length, bolting one end together and folding around your torso directly underneath your armpits. Ensure that your arms go straight down and that the excess metal pushes out in the front and not onto the arms (this causes numbness when carrying a shield). This establishes the shape that all the pieces must conform to. Lay this out on a table and bend the other pieces around a large circular object to start the bend, then bend by hand trying to match each piece with the template. You do not need to try to account for overlap—that will take care of itself after you assemble everything.
Neck Pieces (Breastplate, Top Back Plate & Mid-Collar Plate) If you chose to use 18 gauge and fold the edges under, bending these by hand won't be too hard. If you made the metal templates, simply bend these to the same shape. If you didn't, put on your tunic and sumbarmalis or at least try to mimic shoulder padding and bend these by hand until you reach the shape that fits most comfortably. If you flared the edges and/or went with 16 gauge for these pieces, you will need to use a hammer and anvil. This is another step that requires significant practice beforehand. The idea here is that you will hold the metal at a slight angle to the anvil and strike the metal just short of where it contacts the anvil. This will impart a slight concave bend. If you are using flared 16 ga metal, you will need a fairly heavy hammer and will need to strike the flared edge quite hard (esp. on the mid-collar plate) to get the desired bend. I highly recommend making the thin 22 ga template first so you know the exact shape you need. You do not want to bend too much and try to undo that. I like using a ¼” thick wood block to place underneath the metal to provide the support. I also like using a teardrop shaped hard plastic mallet for the surface as a heavy hammer is likely to leave marks on the surface and is only necessary on the flared edge. Lining your cheap anvil will leather will help avoid unsightly scars on the surface. I won't lie; that mid-collar plate is quite difficult to bend due to the deep curvature of that piece.
Upper & Lesser Shoulder Guards The upper shoulder guards are bent to slightly the same curvature as the corresponding neck pieces. With 18 gauge, you can bend by hand, and you may need to use the teardrop-shaped mallet for 16 gauge to make it easier. The lesser shoulder guards can also be bent by hand in the same manner as the girdle plates.
Assembly & Riveting Pre-Assembly with Machine Screws The first stage of assembly should be to put all the girdle plates together using those 5-40 ¼” machine screws. This will help you determine that the metal is sized and bent properly before riveting as well as verifying that the straps are drilled correctly. This is important, of course, since riveting can not easily be undone. You do not need to tighten the nuts very hard, but be sure to place the nut on the inside and screw head on the outside or it won't go together very well. Repeat this process for the shoulder plates and verify that all the bends and holes are as they should be and make any final adjustments. There's no going back after this point.
Fitting Installation The easiest part of assembly is to rivet the fittings on. Use the rounded head rivets for all fitting attachments. It also helps to use the rivet set for this operation. Insert the rivet through the fitting and through the hole in the sheet metal. Hopefully you kept the fittings well labeled so the fittings match the plates and the holes line up at the proper locations. Place the rivet head upside-down in the rivet set. It helps to place rivets through the other holes to keep it in place. Nip the end off with the nippers, fairly close to the plate. Strike with a ball peen hammer to flatten out the end until it makes a flat, very smooth surface. I find I need to hold off on two of the internal buckles on the top girdle plates, because the leather straps will cover up the holes. Wait to install these until after those straps are in place, then drill though the straps to install these fittings. The rivet on the left is about to be peened. The one on the right is simply there to keep the fitting from moving around.
Riveting The Straps Start with the bottom-most girdle plates and work your way up. Use flathead rivets, with the head on the inside (against the leather strap). You will be peening the end of the rivet directly onto the outside of the plate. This will be covered up once the plate above it is riveted on. Use round head rivets for the top girdle plates, inserted from the outside with brass washers on the inside. After those are done, start with the outermost lesser shoulder guard and work your way in, toward the neck. Use the flat-head rivets just as with the girdle plates. You can also rivet the straps on the back plates at this point (using the 3/16” round-head rivets). Do the upper shoulder guards last, however since they overlap all other pieces (use round head rivets for these as well). Riveting these pieces on can be awkward at this point, but creative use of duct tape and other mechanisms to hold the assembly in place will work to your advantage. Don't forget to use the rivet bosses on the upper shoulder guard rivets!
Final Assembly You should end up with four separate pieces. Before you can buckle these together you need to mark the location where the holes in the belts need to be drilled so the all the pieces overlap properly. You can drill on the drill press or use a leather punch; use a 1/8” diameter hole. Each of these can now be buckled together and you are done! Kindly send pictures to me or post on RAT.
Bishop, M. C., Lorica Segmentata
Price, B., Techniques of Medieval Armour Reproduction: 14th Century
Fournier, R. and Fournier, S., Sheet Metal Handbook
Briney, D., Home Machinist's Handbook
Appendix: Leather & Sheet Metal Measurements