Here's what I found on the Kingdom of "Gleann Abhann" website which Tenessee is in....
http://kingdomofgleannabhann.org/Docume ... ndbook.doc
A. Armor Standards
1. Helms:
a. Helms shall be constructed of steel of no less than 16 gauge. Be aware that some steel sold as 16 gauge measures less than .0625" (1/16" or 1.6mm) and is too thin. Sixteen gauge is the minimum for stainless steel also. Because the mass of the helm is an important part of the protection, no titanium, fiberglass, or other ultra-light materials may be used. NOTE: The finished thickness of metal in a helm must be 16 gauge; beware that dishing can thin the metal. Accordingly, if a spun-metal top is to be used in the construction of the helmet, it shall be a minimum of 14 gauge steel. The process of spinning the top thins the metal, thereby requiring a heavier gauge.
b. All joints or seams shall be constructed in one or a combination of the following ways:
i. Welded on the inside and outside.
ii. Welded with a single bead that extends through both surfaces.
iii. Lap joints, welded or brazed at the edges of both pieces.
iv. Riveted with iron or steel rivets no more than 2-1/2 inches (63.5 mm) apart, or with equivalent riveting techniques. Screw or pop type rivets, along with other lightweight rivets, are not to be used.
c. Welds must be sound and rivets secure.
d. Laced neck guards on Japanese-type helms are allowed providing the lacing material is strong, not frayed, and tied in such a manner that should it break or cut, it will not allow the neck guard to fall open. Upon inspection, any broken laces will be grounds for failure of that piece of armor.
e. Face guards shall prevent a 1 inch (25.4mm) diameter dowel from entering into any of the face guard openings. There is no minimum width of the openings; however, the materials used around the openings must be of sufficient strength to prevent a full force blow from collapsing the opening.
f. The helmet sides and face guard shall extend at least 1 inch (25.4mm) below the bottom of the chin and jaw line when the head is held erect.
g. Bars used in the face guard shall be steel of not less than three-sixteenths inches (4.8mm) in diameter, or equivalent. If the distance between crossbars is less than two inches (2"), one-eighth inch (1/8") diameter bars may be used. Face guard bars should not attach to the interior of the helm, unless of structurally superior design and workmanship.
h. All visors shall be attached and secured in such a way that there is minimal chance that they will become detached or come open in normal use.
i. There shall be NO major internal projections; minor projections of necessary structural components shall be padded. All metal, inside and out, shall be free of sharp edges. External projections must not be excessively damaging to opponents or their weapons.
j. All parts of the helm that might come into contact with the wearer's head shall be padded with a minimum of one-half inch (13mm) of resilient or closed cell foam, or equivalent, or shall be suspended in such a way as to prevent injurious contact with the wearer. Similarly, parts of the helm that might come in contact with the wearer's neck or body should be padded.
k. All helms shall be equipped with a chinstrap or other means of preventing the helm from being dislodged during combat. An equivalent might be, for example, a strap from the helm to breastplate or a chin cup suspension system. A 'snug fit' is NOT an equivalent. The chinstrap should not be so thin or so placed that it could strangle the wearer. The use of a boot or shoestring, leather thong, or cord as a chinstrap is prohibited.
l. Freon-can helms and helms made from mundane military helmets are forbidden
Hope that helps.
Scorpus