These are but my humble opinions based on my research and experiences, and should be viewed as such. I have been a blacksmith for many years, and in the past years, I have specialized in Custom Fire Steels - reproducing original examples from museums, pictured in books, and private collections. And, of course, custom orders from individuals, historical parks, and museums.
Widths vary a lot over the centuries, from 1/2 inch wide or more, on down to 1/16 inch thick or THINNER. Around the Great Lakes fur trade area, a large number of the original fire steels found where 1/8 to 1/16 inch thick, and a bunch were even thinner. There are pictures and discussion of them in the books Where Two Worlds Meet, and Voices from the Rapids. Two very common styles were the Oval and the D or J style (called Single Finger Loop by the Museum of the Fur Trade in their articles). Steel was expensive, so making a thinner fire steel gave you more product to sell/trade for the same material. Example: one oval fire steel 3 x 1 1/2 x1/8 vs. two ovals 3 x 1 1/2 x 1/16. Same material, same weight, two items to sell/trade.
A lot of individual blacksmiths used/re-used old steel to make their strikers such as worn out files. The thickness of that old material tended to be how thick the new striker ended up being. Common files ran between 1/8 and 1/4 inch thick, so the strikers ended up being the same.
The big factories commercially making fire steels started with new steel, and of a consistant thickness. They also tended to make simple styles like the Oval and J styles. And these factory steels tended to be made thin - 1/8 inch thick or thinner.
The only real protection for knuckles is PRACTICE. I scraped many a knuckle until I got more careful with my flint and steel. I also switched to the Pinch Grip - less exposure of those knuckles to that sharp flint. And there are a lot of fire steel styles that require a pinch grip.
A wide striking surface offers more area to the flint to get your spark - like a flintlock frizzen. But a thin edge concentrates the force into a small area to make it easier to dig out those little bits of steel for your sparks. I prefer a thin striker - 1/8 inch thick. With a thicker striker, I tend to tilt it to the side to strike more on the edge anyway. It comes down to personal preference and what works for you.
I have used a lot of old, scrounged steel over the years to make strikers - hay rake teeth, fork teeth, car springs, lawn mower blades, leaf springs, garage door springs, files, rasps, etc. It's nice to be able to re-use some old material, but there are problems associated with that. First, you never quite know what the steel really is - alloy and carbon content. Old steel like springs also tend to have some work "memory" in them, along with years of work stress/cracks. These tend to show up after all your forge work when you are heat-treating. Really frustrating when that striker cracks during the quench, or breaks on the first couple hits on the flint. (Or when you drop it a inch or two onto a wood table!) So I prefer to start with new steel - just like many of the knife makers. You know what the steel is, how it will work and heat-treat, and you don't have to worry about its past history coming back to bite you.
A great source for cheap new steel for strikers is your local farm store. They carry new replacement hay rake teeth. It's basically 1095 or W1 spring steel, and generally is about 1/4 inch round stock. Some are smaller at 3/16, and some run up to 5/16 thick. The local Farm Fleet store sells the 1/4 thick hay rake teeth for about $1.09 each, and you end up with about 3 feet of rod after you heat it and unwind/straighten it out. It's a great size for those classic C strikers which use somewhere between 6 and 9 inches of material.
I quench my strikers in water, and I quench the the whole striker at once. Almost every time I try and do the differential quench, I end up with cracks - quenching the striking surface first, then the rest of the striker. So I have been just quenching the whole striker at once. This has been giving me excellent results. But, I have also been using a knife-makers trick on my strikers. I "thermal cycle" them. After forging, I heat them up to that non-magnetic point, and pull it out to air cool till no color. I do this three times, then I do my final heat and quench. The thermal cycling relieves a bunch of internal stress in the steel from the forging process. This little extra step has almost eliminated any breaking/cracking problems. I was amazed at how well it worked.
These are a few of my humble thoughts and observations on fire steels to share. I hope this helps answer some of your questions. I do have a web site set up with lots of pictures and information on fire steels
www.angelfire.com/journal2/firefromsteel (I really need to update it with more info and pictures - one of these days.)
These are but my humble thoughts, experiences, and opinions, and are best used in conjunction with your own research.
Mike Ameling
