slowpokebr549 said:
So, forgive my ignorance, but what color should you heat one to temper it. How hard should it be, I assume not white hot from your testing method.
In heat-treating, there is a point in the "red" color range where a magnet will no longer stick to the steel. That is the critical heat-treat temp. When you quickly quench/cool your steel as it is at that temp, it will now be a as hard as you can get the steel.
And that is when a flint striker will work the best - when it is as hard as possible. But it will also be brittle at that point, and likely to crack/break from the shock of striking sparks. The knife makers will selectively heat their blades back up to ... draw the temper ... back a bit from this point - to make their blades less brittle, but still hard enough to work well as a knife blade. But a knife blade ends up being too "soft" to work well as a flint striker.
So you need to take other steps to reduce the final brittleness of your flint striker. The BEST TIP I ever got on this came from a knife maker. He told me to "thermo-cycle" my flint strikers before the final quenching. To thermo-cycle, you finish forging your steel striker to final shape. Then heat it up to that critical temp where a magnet will no longer stick to it. Now pull it out of the heat and let it air-cool until you do not see any red color in your striker. Now do this two more times. Then heat back up to critical temp and quench in water or oil. Your striker will now be as hard as you can get it, but also be far less brittle.
That "thermo-cycling" removes any internal stress in the steel from the forgin process. It also shrinks the internal grain structure in the steel. The smaller the internal grain structure, the less brittle it will be. If you heat your striker up past that critical temp, the grain structure starts to expand once again - just like when you were forging it.
So that tip about "thermo-cycling" the striker before the final heat-treat quench was the best tip I ever got in making a good flint striker.
The other thing to remember is to start with good high-carbon steel. Some modern files have junk low-carbon steel inside them, and were case-hardened on the outside. So only the teeth have that high carbon content. So they won't make good flint strikers, or good knife blades either. So test the inside of any file you might want to make a striker or knife blade from - before you put all that work into it.
I prefer to use new steel when making flint strikers. I either buy new stock from a steel supplier, or I go down to the local farm fleet store and pick up some "agricultural" steel. Lots of agricultural steel is made from 1080 high-carbon steel - like hay rake teeth, and bolt on plow shares and cultivator points. And the price is generally less than buying new bars/rods from the steel supplier. Those modern hay rake teeth are generally 1/4 inch round rods, and around 30 to 36 inches long - after you straighten out the coils/bends. You can make 5 to 6 good C strikers from one rod - which will cost around $1.30 per rake tooth. 5 inches makes a good classic C striker that will fit most hands, and 6 inches works a little better for large hands.
For "scrounged" steel I look for lawn mower blades. They are generally made from either 1084 or 5160 steels. The hardest part is cutting/chopping them up into small pieces to make into your strikers or knife blades - and working around the holes in the center and any letters/numbers stamped into the original lawn mower blade. And you can generally get them for free.
Garage door springs can work well. But you can also run into problems with stress cracks that built up over the years, and some inconsistent alloy content inside the springs themselves. So occasionally one section of spring will work and heat-treat differently.
Hope this helps.
Mikey - that grumpy ol' German blacksmith out in the Hinterlands
