Need a harder spine

jtdesigns

jtdesigns

Joined
May 2, 2011
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Ok, so I have a standing order for a somewhat well known survivalist/bushcraft personality and one of his requirements is that the spine must be hard enough to throw spark off the spine from a flint/chert/quartz. Right/wrong/indifferent, it is a requirement. The steel is 1095, my oven is programmed correctly, using Parks 50. Blade edge turns out great but wont throw sparks from the spine very well. Ended up having Peter's heat treat this model because their process gets the spine hard enough. The only thing I can think of that differs is "rack" I am using which is a fire brick with a shallow kerf cut in to hold the blade in an edge up position. I am guessing that the spine which sits in the kerf is being somewhat insulated from the heat and not reaching critical temp. Also could be the cryo process that I am not set up for but Peter's does. Any thoughts on this?
 
1095 has a pretty low Mf. The cryo will convert a large portion of the RA to martensite increasing the blade hardness before temper. Peter's might be tempering at a lower temperature or for a shorter period of time leaving a harder, but more brittle, blade.
 
Is it possible the spine on the one treated by peters is just crisper? The spine needs to be pretty square and sharp to throw good sparks off a ferro. Other than that I am not sure. If you are running a soak and the fire brick is up to temp in the kiln the spine should not really be staying cooler than the edge, unless the soak is possibly shorter than it needs to be. Just one opinion, and probably worth exactly what you paid for it haha
 
Grayzer86 said:
Is it possible the spine on the one treated by peters is just crisper? The spine needs to be pretty square and sharp to throw good sparks off a ferro. Other than that I am not sure. If you are running a soak and the fire brick is up to temp in the kiln the spine should not really be staying cooler than the edge, unless the soak is possibly shorter than it needs to be. Just one opinion, and probably worth exactly what you paid for it haha
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But this wasn't using a ferro but a rock. The difference being that with the ferro the sparks are from the ferro but with a flint they are from the steel. The other thing that I see is that a typical steel is run along the flint not across it so you might have issues with one tool acting like a knife and a steel for flint and steel.

this thread suggests that softer might be better for a flint and steel effect

http://www.survivalistboards.com/showthread.php?t=167087

This http://www.instructables.com/id/Firesteel-forged-vikingstyle/ suggestes that higher carbon than 1095 might be even better and seems to just harden and not temper the steel.
 
Understanding how flint and steel works is how to deal with this situation. You may want to educate your customer.

In traditional "Flint and Steel" -The "steel" only needs to provide very small iron shavings. The flint needs to be hard and sharp to shave pieces off the steel.
In using a ferro-ceramic rod - The "steel" needs to be hard and sharp edged to shave pieces from the rod. While often called "flint and steel" it actually works the opposite way.

What makes a fire using a traditional flint and steel is a neat thing called the pyrophoric property of iron. Pyrophoric means that the metal will burn in oxygen at low temperature. We all think of sodium and lithium, but many other metals will do this, What keeps these metals from bursting into flames is the oxides that coat them. These oxides form almost instantly with exposure to air, and protect the metal from the oxygen. However, if the piece of metal is small enough, and the surface is not oxidized yet, it will instantly burst into flame. Iron is great for this because it isn't too reactive, like the lighter metals, but still has pyrophoric properties.

When you strike a piece of steel against a flint, the sharp edge of the flint shaves off tiny pieces of steel. These have un-oxidized surfaces that instantly catch fire. These are called sparks. The higher the carbon content ( up to a point), the hotter the shavings burn. 1-2% carbon is perfect. The steel needs to be softer than the flint, so the flint can easily cut it. However, harder steel shaves off thinner and smaller pieces, which burn faster and hotter. The middle ground is a moderately hard steel and a very sharp flint. Flint and Chert are used because the edges chip in a concoidal fashion, always exposing fresh sharp edges. If the steel is too hard, it just chips the flint. If the steel is too soft ( as in the annealed state or pure iron), the flint shaves off too big of a chip. Between 1% and 2% carbon and a hardness in the mid to upper Rc50's works perfect. It may be counterproductive to have the steel too hard.

Any hard ands sharp object can make the sparks. Most quartz rocks will work fine. Even a harder piece of steel will work ( as un using a file to strike the spark). However, time and trials have found that flint/chert works superb.


In using a ferro-ceramic rod, the hard and sharp steel edge shaves off a few tiny slivers of the rod. The metal mix in the rod is made to quickly react with the oxygen in the air and burst into flame. The other ingredients in the rod make the flame hotter and the spark longer lasting.




Contrary to the popular movie image of a caveman with two rocks - striking two rocks together will not be likely to start a fire. The tiny sparks seen when that is done are just hot fragments of rock. These just cool off, and do not actually burn. Another reason you see sparks when two pieces of quartz are struck together is called a piezo-electric discharge. Again, it gives off light, but not much heat.
 
If you really want to see the flammability of steel, touch a nine volt battery to some steel wool. A good fire starter as well.
 
So what do you think is the primary difference between my heat treat and Peter's regarding the difference in spark throwing?
 
As he said it needs to be hardened some it could be that you aren't getting it hard enough, after hardening do you file test the spine for hardness? If it is still annealed it won't work well.
 
When I make steels They are quenched in water with no temper, just a grind to the face to remove decarb. Imho harder makes better sparks, and they break sometimes. I'm not sure a knife hardened enough to throw good sparks would last very long as a knife.

mark
 
Perhaps you need to develop a different temper process. My best guess is that Peters cryo would be the reason or perhaps their quench is slightly faster than yours, missing the pearlite nose. So, what if you do a snap temper at 300 F after quench. Then take a pan of sand at say 425 F and place the edge of the knife in it. Leave it until the spine gets to hot to touch then cool in water. Repeat as necessary until the edge and blade about halfway up are at the right tempered hardness. Test the spine to see if it will throw sparks. Adjust your process to optimize for the edge hardness and spine throwing sparks. You can use the same blade for each test, just clean the decarb off each time.
 
Did you grind the decarb off of the spine? you need to grind a significant amount off for it to cast sparks. I did an experiment with steel strikers back in 2007 and was able to temper them as low as 54HRC with decent spark results. I also noticed that my striker got better with more use... that's when I started grinding more off after heat treat.

As long as you aren't spring tempering the spine, edge quenching or clay coating, you should be okay. If you think the spine isn't getting hot enough, put a couple of refractory spacers under the tip and tang to hold it up.

Another thing you might want to try(If you aren't doing this already) is quench spine down. I do this anyway to help prevent warp and tip-dip(kind of a reverse sori).

I see folks making strikers as hard as they can, without tempering and it makes me cringe. Temper everything!
 
I am really interested in how this turns out. I am planning on making some strikers this year and the results of your tests will help me decide where to start my tempering from.
 
It has been a long time, but I used to make some strikers in demos at the scout camp. I would use 1/4" square mild steel and draw out the ends, twist and curl it, shape into a "D", etc. Then I would quench in the slack tub. I would give it a "flame temper" by heating the handle parts, but keeping the flames off the striker bar. It was somewhat hard, and gave great sparks once you learned how to use a steel. Most kids would just whack the steel on the flint and get nothing. Once they learned to glance the steel against the edge, they shaved off hot sparks.
We made the boys wear a glove when learning, as more than once they hit their knuckles on the flint instead of the steel :(
 
Bo T said:
I am really interested in how this turns out. I am planning on making some strikers this year and the results of your tests will help me decide where to start my tempering from.
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Heh, heh.... not to sound like a smart-aleck, but start from full hard. Use the appropriate quench medium for the steel. You don't need to get a striker any harder than a knife. Temper at 375F for an hour(at least). I do mine at 400F. They shouldn't shatter if you drop them on the concrete/stone. Essentially, a striker is an impact tool(hence the name "striker")
and should be treated as such. In the field or for demos, you do what you can. Obviously, they didn't have toaster ovens back in the day so as Stacy said, a good eye and a bit of patience can yield a great working tool.

I messed around with traditional(and not-so-traditional) flint and steel for years. Strikers, stones, tinder, etc... lots of combinations. I've got a thread somewhere in WSS, when I used a knife, a flake of chert no bigger than a rolled oat, and a single thread of cotton fiber(un-charred). Good times.
 
This is great information guys! I was thinking about getting some W1 drill rod. And from what Stacy said about the mild steel he used, it should work well even if I end up with 60 points of carbon. These would be forge tempered, Rick. I'd probably run a blue temper around the sides and start with the palest yellow I could see along the striker. If it ended up too chippy, I'd temper it back a little. Should I worry about normalizing the striker beyond a stress relief cycle? One fellow said that he believed large grain size was good for a striker.
 
Bo T said:
This is great information guys! I was thinking about getting some W1 drill rod. And from what Stacy said about the mild steel he used, it should work well even if I end up with 60 points of carbon.
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I didn't catch that mild steel part. Are you sure it was mild steel, Stacy? (A36, 1018/20) I have never had steel below 1045/50 work and 1045 was so inefficient that it wasn't worth the effort. I'm just wondering if it was "unknown" mild steel.

Bo T said:
Should I worry about normalizing the striker beyond a stress relief cycle? One fellow said that he believed large grain size was good for a striker.
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Large grain is great for casting sparks. It is also great for smashing into pieces. Fine grain, tempered martensite is the best. You have to put into perspective what you want;

-steel with high hardenability(carbon content)
-no stress-cracks during the quench(fine grain, avoid overheating)
-high HRC(full quench, agitate)
-tough enough not to fracture during use(temper appropriately)

Sounds an awful lot like what we look for in a knife. Heat treat it like a knife.
 
Yes, it was plain old HF 1/4" square. I water quenched it from what I would guess was 1500F. Mild steel will get hard enough to snap like glass with a water quench. I drew it back to what was probably low to mid Rc50's. If left full hard, they broke too easily. This was for a demo, and if I had 1050-1095 steel, it surely would have been better. Still, it works just fine for making sparks that would ignite tinder. We were using char-cloth and fine pine shavings for tinder.
 
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