This is a medieval crusader great helm I built, replicating an actual great helm, but using modern building techniques.
18 guage Sheet Metal
Metal Jig Saw
Gold Spray Paint
Step 1: Paper Pattern
Start by taking some construction paper and shaping it in the form of your helmet.
You can copy my flat pattern or make your own.
Doing a paper pattern allows you to alter your shape and size easily before you move to metal.
Once you get it to the right size (make sure to leave room for padding) you can cut apart the paper pattern into individual sections. Keep in mind where you break the sections, there will be a seam there. You can do it authentically or more modern.
Step 2: Metal Pattern
Transfer the paper pattern to 18 gauge sheet steel. Simply trace it with a sharpie then cut it out.
I used both a nibbler and metal shears to cut it out.
Now bend the sheet metal into the shape of your helmet. All you need is your hands and maybe some leverage. You don't need to dish it.
Use some tape to hold it in place to make sure it's all accurate before you begin welding.
Step 3: Weld the Body
Now you can weld the sections together. Yes rivets are technically the traditional way to built these helmets, but we live in the modern world and welding gives it more security. But by all means, if you want to replicate it, try just riveting it.
I used a mig welder. Adjust the settings to what works best for you. Please know how to weld before you jump into it.
Try to do most of the welding on the inside, less cleaning to do. I welded the sides all from the inside, this way it looks like the rivets are actually holding it together, instead of just for show. For the top I welded both inside and out then used an angle grinder to clean up the welds.
Step 4: Visor Decoration
This is where you can alter your design. Research some actual visors, or create your own.
Create the visor the same way as you did the helmet body. Paper Patter > Metal Pattern.
Once you have it cut out and bend to the shape to fit the helmet, paint it. I spray painted it gold first to give a nice base coat. You will have to do touch-ups later, but it is easier to paint it while it is separate from the body.
To keep the edges clean I spot welded it from the inside of the helmet.
You may have to file open the eye slots more once it is welded in place, in case is slipped or is a little off.
Step 5: Add the Rivets and Bring It to Life
Rivets really accentuate the helmet.
I used larger ones for the body of the helmet and smaller ones along the visor.
For a more authentic look, run rivets along each seam. Again mine are just for show, but traditionally rivets actually held the different section together. You can actually rivet it, or if it's too tricky to work the rivet from the inside, just tack weld them from the inside.
Step 6: Ventilation Decoration
To make it easier to breath while wearing it, and to look even better, pick out a ventilation decoration and cut it into the face of the helmet.
I stuck with the cross theme, but you can put in a family crest, or just do something on one side. Make it your own.
Be sure to grind and file down the inside to keep it smooth and free of burrs.
Now before we line the inside, finish off the outside. I buffed the steel to clean up any deformities and touched up the visor with more gold spray paint. Hit it with a little FEV (French Enamel Varnish) if you wish, or paint the body of the helmet, or paint nothing.
Step 7: Line the Inside
Time to pad the inside to make it more comfortable to wear.
Cut upholstery foam to the size of the top section and layer it in up against the top. Cut it a little big and all you have to do is press it in and it will stay on its own. Put it on to see if your eyes line up with the eye slots, adjust the foam accordingly.
Line the rest of the inside with craft felt, attach it to the metal using barge. This will protect the users face from rubbing up against the metal and make it more comfortable to wear. Be sure not to cover up the eye slots or vent holes.
Now your crusader great helm is ready for battle...or at least a crazy night on the town.
Be sure to keep the helmet oiled to keep it from rusting. I oil mine once a month with a rag.