Exerpted from "I Forge Iron" forum

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08-18-2009, 09:11 PM
Mike Ameling  
Senior Member         Join Date: Mar 2009
Location: NE Iowa - USA
Posts: 453

 
Several issues here.

First is the springs. Garage door springs can and do make good strikers. They have enough carbon content in the steel. But they also can have problems with internal work stress from their former profession. Plus, they can vary in the actual metal alloys in them. They are made to a minimum specification to work as springs, but the alloy mix can run higher. So you can run into sections of a spring that just won't work right - inconsistent on the heat treat.

The other part is the heat treat itself. To work well as a flint striker, the steel must be just about as hard as you can get it. That allows the sharp edge on your flint to chip/dig out little bits of the steel. The energy of chipping/digging out those little bits of steel (and breaking some molecular bonds) heats those tiny bits of steel up hot enough that the carbon in them burns. Those are the sparks you see - the carbon burning/twinkling.

But when you harden high carbon steel, you also then make it much more brittle. So then you need to take other steps to help reduce that brittleness. The BEST tip I ever got about making flint strikers came from a knife maker friend. He said to Thermal Cycle my striker before the final quench. That Thermal Cycling does several things. First, it removes any internal stress in the steel from all the forging/bending. It also then shrinks/refines the steel grain structure. The finer the grain structure, the less brittle it will be.

That simple "tip" was the BEST one I ever got over the years. After I started doing that, I have had almost no strikers break in normal use. Before that "tip", I would forge up a striker, heat treat it, test that it sparked well, and then set it on the workbench to work on something else. I would then often hear a little "tink" behind me. When I looked back the striker would now be in two or three pieces. Or I would drop one on GRASS and it would break. Thermal Cycling cured all of that, while still leaving the striker hard enough to spark well in use.

To Thermal Cycle, you forge up your striker as usual. Then you heat it up to Critical Temp (where a magnet will no longer stick to it), and pull it out of the heat. You then let it cool in the air until you don't see any color. Now do that same thing two more times. After that last air cooling, you now heat it back up to critical temp and quench it - in your choice of water or oil.

Personally, when I quench my strikers, I quench the WHOLE striker at once. If I have some thin areas, or really drew out the ends a lot, I will selectively heat those thin areas back up to temper some of the hardness. I've tried to quench just the striking edge before, but I usually end up with cracks. So I just quench the whole striker, and selectively heat back up any thin ends to soften them up a bit.

This works for me. I make around 500 to 600 flint strikers a year, and have very very few that crack/break in normal use. Plus less than 10% of those strikers are that classic C shape. There are dozens of other shapes/styles to make - from very early Roman times B.C. on up to the present. I am personally pretty fond of the Viking era strikers, and the Scottish style. But most I make are based on originals dating from the 1600's and 1700's. And then there are my little Whale buddies - flint strikers shaped like sperm whales. They date to the late 1700's, but mostly early 1800's. There are pictures of them, and many other striker shapes in my Gallery photos.

I hope these rambling thoughts help.

Mikey - that grumpy ol' German blacksmith out in the Hinterlands

p.s. There are many BAD strikers out there. Ones that you have to POUND your flint against steel just to get a few weak sparks. Those are extremely frustrating. And most are just not heat treated HARD enough. Too many heat treat similar to a knife blade. But that is generally too soft to work well as a flint striker. They need to be HARD, like the cutting edge of a wood chisel.
 
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08-18-2009, 09:21 PM
Mike Ameling  
Senior Member         Join Date: Mar 2009
Location: NE Iowa - USA
Posts: 453

 
A final note. NEVER tap a flint striker with a hammer AFTER you quench it! Do any/all tweaking and straightening BEFORE the heat treat. Even clamping one in the vise to do a little filing/sanding of a sharp edge might crack/break it. You may have "tempered" the ends back a bit, but they still are hardened tool/spring steel. Plus the shock waves from any "tapping" will travel through the rest of the striker.

Now, to combat the brittleness problems with normal flint strikers and how hard kids can be on them, I did come up with what I call a "kid proof" oval striker. After all the forging and heat treating and testing, you can lay it down on your anvil and hit it a dozen HARD FORGING BLOWS without it breaking/cracking or chipping. And it will still throw great sparks. I made these up for Boy Scout and Kid's camps - to use when learning to use a flint and steel for fire starting. It amazes people who have made flint strikers before, to see me smack one on their anvil - even standing it up on edge and hitting it HARD with a hammer. The San Diego Council has now gotten around 4 or 5 dozen of them from me for their big summer camps. And they have only had a problem with ONE - it got lost, dropped to become lawn mower bait, or wandered away in somebody's pocket.

Mikey

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08-19-2009, 12:28 PM
Mike Ameling  
Senior Member         Join Date: Mar 2009
Location: NE Iowa - USA
Posts: 453

 
Quote:Originally Posted by UnicornForge  
Am I understanding correctly. You said don't tap a flint striker with a hammer after heat treating, instead place it flat on the anvil and hit it with a dozen hard blows from the hammer?

I would greatly appreciate an explanation of what hitting it *hard* with a hammer *after* heat treating is doing to the structure of the steel to make is safe from cracking.
/quote

This is ONLY with those KID PROOF strikers that I came up with! Doing that with any normal high carbon and properly heat treated flint striker would shatter it. But those KID PROOF strikers are different - specifically made to NOT break when being abused by people who do not know or have not developed enough skill in using a flint striker.

I also made them for a national park - for the use of the kids they hire for the summer as interpreters. Too many of them just don't care about their job - it's just for the summer and to make a few bucks for college. So they are not very concerned about the tools and gear they use in their interpretations to the public. The one regular park employee called them ... poorly trained monkeys.

So that specific comment was ONLY about those specific KID PROOF strikers.

I hope that clarifies things.

Mikey

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08-19-2009, 07:24 PM
Mike Ameling  
Senior Member         Join Date: Mar 2009
Location: NE Iowa - USA
Posts: 453

 
 
Quote:Originally Posted by piglet_74  
The kid proof one would be interesting to see. Could you post a pic? Or was it mainly the heat treating process you described that makes it that way? Thanks, Rob.
/quote

There is nothing special about their look - although they do tend to be about twice as thick as my normal oval strikers (close to 3/16 or 1/4 inch thick). They are basically a version of case-hardening. The insides are soft iron with that high-carbon outside that can be heat-treated hard for good sparking. That soft core gives them the strength to resist cracking/breaking. I'll see if I have a pic around somewhere - probably in my Gallery photos.

When I first made them, I was concerned about how long that "case hardened" layer would last. So I took one and struck sparks for 1 1/2 hours straight - only stopping long enough to get a new sharp edge on my flint. I didn't see any lessening in the sparks. So I then took it to my bench grinder. I had to grind away almost 1/4 inch of the striking edge before I saw a noticeable decrease in sparks. That equates to YEARS of hard use as a flint striker. But I could still get some sparks from that edge - just less. So I haven't worried about it since.

They are great for Kid's Programs. You don't have to worry much about the kids damaging them with miss-use.

And one of my next experiments will be to take wrought iron, forge up a striker shape, and see about baking it in a crucible full of bone/leather scraps - to case-harden it in an old traditional manner. Just an experiment to see ...

Mikey

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08-20-2009, 11:53 AM
Mike Ameling  
Senior Member         Join Date: Mar 2009
Location: NE Iowa - USA
Posts: 453

 
How do I make those Kid Proof strikers and get them case-hardened?

Aaaah, trade secret times!

The answer is pretty simple - I use iron that is already case-hardened from the manufacturer. I just make sure that I don't "scale" it too much when forging to shape. Any surface scale removes a bit of the case-hardening on the original steel/iron.

So here's the secret ....

I start with some hardened chain links. They are the cross-links from truck/tractor chains - the type you put on the tires for extra grip in snow and mud. The side chains are regular soft iron links, but the cross chains are case-hardened to hold up longer in use. And it's a pretty good/thick case hardening. Yes, you do have to clip every other link to get one complete link to make an oval flint striker, but you can use the cut links to make other styles of strikers. The big point is to not create too much scale on the part that will be the striking surface on your flint striker. That is where you want as much of that case-hardening left on as possible.

Now, I'm not quite sure what the base metal alloy really is inside. When I cut a link cold on one side and then twist it to clear, it will sometimes break instead of bend/twist. So that internal metal might have some carbon and other alloys mixed in. It just doesn't spark well as a striker if you get through that case-hardened outside layer. So I try to keep the re-shaping of the links to a minimum - on the sections that will be the striking edge. Mostly just flatten it out and true up the edges. But, like a said before, I had to grind in 1/16 to 1/4 inch before I got through enough of that case-hardening to start to affect the number and quality of the sparks I got from the finished oval flint striker.

The specific chain I've been picking up at the farm store is from Peerless - part number 3017112 and designated on the tag attached to the bag 7/0LL TW CC HARD B 100' /BA That HARD designation is the indication for case-hardened. This makes into a pretty nice sized oval flint striker in a fairly common original fur trade era size - around 3 x 1 1/2 and around 3/16 inch thick. The larger cross chains make into larger strikers. I've even messed around a bit with some car tire chains, but the small size becomes a problem.

I had been getting the bulk chain from the local farm store (cut to your length from a 100 foot bag) for $3.50 to $3.75 per foot. There are around 26 links per yard, which then gives material for 13 oval strikers per yard - or around 4 oval strikers per foot. So materials costs ran less than a buck each. And the cut links can still be used for other styles of flint strikers as well. But last year when steel prices went crazy, the price per foot jumped up to $8.75 per foot! I still bought some chain, but that really cuts into the cash flow. But it's still pretty good, since I make between $15 and $25 for every two links of chain, or $60 to $100 per foot of chain. There's still fuel costs and the labor, but not a bad return. My oval strikers retail for $15 each (either the all high carbon ones or the Kid Proof ones), and the C's and simpler styles for $12 each.

There. Now you know ONE of my ... secrets! Am I worried about sharing that? No. I know the work involved, and anyone willing to do that work is welcome to it.

Have fun ... torturing iron!

Mikey - that grumpy ol' German blacksmith out in the Hinterlands

p.s. I had orginally been looking for some chain made from high-carbon steel - to use to make oval flint strikers and skip that "welding" part. But I didn't find any. Although I did keep running into references to "hardened" chain. So I tried some. That's when I found out about using the case-hardened chain links, and how "tough" they end up being in use. Now I just have to find a good use for 35 feet of non-hardened chain. It was being sold for cross links on truck/tractor tire chains, but turns out to not be case-hardened. I never got a chance to spark-test it on a grinder before I bought it.

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08-21-2009, 10:18 PM
Mike Ameling  
Senior Member         Join Date: Mar 2009
Location: NE Iowa - USA
Posts: 453

 
Before you start forging on a chain link, do a spark test on it. Be sure that you see lots of short twinkling sparks when you touch it to a grinder. That should show you if it is really case-hardened. You can spark test it on the narrow end of the link, since that area will not be part of the striking surface of your final striker.

But try hard not to scale up that chain link too much when forging it. And scale will decrease that case-hardened outside layer on the chain link. So flatten out the twist in the original chain link, flatten it out and stretch its length to where you want it, and do so with as few heats and little scaling as you can.

Because of how well those chain links worked into good flint strikers, I also tried to forge the cut links into other styles/shapes of flint strikers. But that is where I found out about losing that case-hardened outside layer. I scaled them too much in the forge, and I ... shifted ... the metal around too much - redistributing that high carbon layer. Some worked OK. Some worked poorly. And some just wouldn't spark. Lesson learned!

Have fun with your project!

Mikey - pondering what other "trade secrets" to share

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08-25-2009, 01:55 PM
Mike Ameling  
Senior Member         Join Date: Mar 2009
Location: NE Iowa - USA
Posts: 453

 
Quote:Originally Posted by trollkeep  
Some files are case hardened. I have never paid attention to brand. They act real strange for most things but sound like they would work for tough strikers.

David Childress
Rocky Forge Blacksmith Guild
/quote

A case-hardened file will not make a good sparking flint striker. Only a few thousandths of an inch of the surface/teeth of the file have enough carbon content in the steel. The insides don't have enough. And you generally remove the teeth from the striking surface anyway.

Lots of the recent cheapo files are soft iron that has been case-hardened - like most from China/India/Pakistan. But some still are made from good high carbon tool steel all the way through. Nicholson is one brand still being made of good tool steel. And lots of really old ones were made that way. Most people who want to forge a knife from a file will cut off a short section from the end and then see if it will heat-treat -- before they put all there time into forging/grinding/filing up a knife blade that doesn't have enough carbon content in the steel to properly heat-treat. As a friend said, it's a hard lesson to learn - when you spend 40 hours finishing up a knife blade from an "unknown" file only to find out that it is poor steel when you try to heat-treat it. Throwing that 40 hours of work into the scrap pile teaches you a hard lesson.

So check out any file first. A quick test it to clamp it in your vise with a couple inches sticking up above it. Then drape a shop rag over it and smack it on the side right above the vise jaws. A file with good tool steel all the way through it should snap right off. You can then spark-test that broke edge on your grinder. You should see lots of short twinkling white sparks instead of long dull red sparks. Those twinkling sparks are the carbon burning. The long dull red sparks are just the hot iron ground off by the grinder.

A quick NO FORGING striker can be made from a good file by snapping off about 3 inches of the end of the file. Then carefully grind the teeth off of the narrow edge of the file - cooling it all the time. If it is getting too hot to hold in your fingers, cool it right away. You don't want to see the metal starting to turn blue from the grinding heat. This will leave the original heat-treat in the file. But those file teeth interfere with striking sparks with flint, and really chew up your flint fast. So grind down to bare metal. And also ground off any sharp edges where you snapped it off - saves cuts on fingers. And there is your flint striker. Just grip in with a "pinch" grip between your thumb and fingers, and strike your sparks from a sharp edge on your flint. Simple basic flint striker - without any forging or heat-treating. Many Boy Scout troops used to do this a project. Make your own flint striker, and then learn to use it to start a fire.

Just a few humble thoughts to ponder.

Mikey - that grumpy ol' German blacksmith out in the Hinterlands
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"Man will never be free until the last King is strangled with the entrails of the last Priest" Dennis Diederot 1763
 
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