jmccustomknives
I see it all the time on social networks, someone  will post a pic of them spark testing a piece of steel and ask, "Is this good".  Got me to thinking, so I came up with this video set up as a game.  I test 12 pieces of steel and the viewer guesses what they are.  Answers are at the end.  Ironically, I posted this video to some of those pages and while that newb asking will get 50 opinions I have gotten almost none.  Those "experts" disappeared.  lol.  Of the ones that have taken the challenge, 3 has been the highest number gotten right.  

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

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RaymondRife
I thought #5 was mild steel, I've ground enough of that stuff to fill a 44 gallon drum with dust. I think I just knew the sound more than anything.

As for the rest, I had absolutely no idea, it seemed like the harder they got the higher the pitch the wheel was ringing. That was confounded by the colour of the spark and the way it reacted though.

I've sharpened almost everything with a blade or a cutting edge on a tool and cutter grinder too.

When it all comes down to it, I really can't tell unless it's HSS, tungsten carbide or mild steel as they were the 3 main steels/ metals I used to regularly put on a grinder.
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Hank Rearden
Brilliant. I'll give it a go.

  1. L-6
  2. nickel
  3.High speed
  4. tungsten
  5. Maganese
  6.51200
  7. o-1
  8. 5160
  9. 1095
10. d-2
11. 15n20
12.nickel

completely missed. although I first thought three was wrought
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Skarzs the Cave Troll
Heh.
I didn't really guess for myself (sorry), because I have found the spark test to be rather inconclusive, and don't use it much.
I did a demonstration on this, and how to test what a steel is. The spark test can show some things, but not everything. For example, some high alloy steels that are high in carbon prevent flowery sparks, and unless other testing is done, a person might think it is just mild steel. S7 (an air hardening steel) is one of them, though it almost looks like a mix of sparks between wrought iron and tungsten carbide.

In my opinion, if you have an unknown steel, it should be spark-tested, quench tested, then broken.
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jmccustomknives
Skarzs the Cave Troll wrote:
Heh.
I didn't really guess for myself (sorry), because I have found the spark test to be rather inconclusive, and don't use it much.
I did a demonstration on this, and how to test what a steel is. The spark test can show some things, but not everything. For example, some high alloy steels that are high in carbon prevent flowery sparks, and unless other testing is done, a person might think it is just mild steel. S7 (an air hardening steel) is one of them, though it almost looks like a mix of sparks between wrought iron and tungsten carbide.

In my opinion, if you have an unknown steel, it should be spark-tested, quench tested, then broken.


That was exactly the point of the test, to show that sparks shouldn't be the only test to determine the viability of a steel for knives.




Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

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Skarzs the Cave Troll
Oh. I didn't get that from the video. If I'm honest, I think some people may take that the wrong way, and study the sparks to try to memorize what is what. (I know a couple characters who would do just that.)
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jmccustomknives
Skarzs the Cave Troll wrote:
Oh. I didn't get that from the video. If I'm honest, I think some people may take that the wrong way, and study the sparks to try to memorize what is what. (I know a couple characters who would do just that.)


Well, there's nothing wrong with using sparks to point you in the direction.  When done it's best to have a known samples to compare with.  

Yesterday a gentleman came out wanting to see if I could take some old files that were his dads (this guy was in his 60's).  He had two old half round files, well one was a rasp.  The wood rasp was a large one and I'm always suspicious of them.  It had "American" in the name.  The half round bastard was smaller and for metal work.  I asked if I could do the spark test.  First I hit the smaller ones tang, it's spark was very indicative of high carbon tool steel.  Exactly what I would expect.

I hit the wood rasp on the grinder.  I was shocked, it's spark was very close to what you'd see from a RR spike.  I wish I'd got those on video.  It's the main reason I won't use rasps.  That was was a case hardened one.

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

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anvil
I would fail that test with sparks -a-flying.

However, I look at the process in a different manner. And claim it is pretty right on all the time if you do it as I do.

JM hit it close, always have a known sample to compare the unknown one to.

So, heres "the way", and always run like hades when you hear those words,,, "the way!"

To memorize spark patterns for even the common known steels would be a never ending task! So i have never memorized spark patterns, i always compare with a known sample.

Heres my process. Let's start with an unknown 5/8" round coil spring. On a sample of this, do all that Jm indicated. Spark test, harden and break test, quench medium test, and experience that grows with each unknown sample. Now, I dont have a clue on what this is is called, wxyz56, or whatever. But I do know forging temps and how to heat treat. And as I use it, I learn what is it's best use. So, when you come across another 5/8" round coil spring, spark it against your known. If they match, you are 100% sure how to work it. If not, repeat the above and call it 5/8" round #2.

Want to know if its 4140? Go buy a sample, label it via name and source. Do this because the sparks from two different companies may differ. Now spark test to your shop samples.

As a blacksmith, the above is all the data I need. So keep good notes as well.

As a knife maker, you need to know all those fancy terms and numbers because your clients expect it.

I'm sure glad I'm a mere simple mountain blacksmith. [wink]

Merry Christmas, one and all.

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Hank Rearden
I picked up a guru book on tool steel at the antique store.  There's a chapter on spark test. Basically it says you must know your sample steel. (Have a dedicated simple tray) use the same speed abrasive surface. Same grit and same pressure each time. Then practice, practice, practice. 
Or send it to the lab.
code[Maglio.gif]  Keep the fires burning hot!
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Marc
Just to be pedantic ... a spark test is not subjective, since the same steel will make the same sparks regardless of the operator. It does require practice to tell what steel it is and surely it is not a fool proof method but a good practical way to tell what it is within reason. I don't make knives or lathe tools so All I got is that number 3 is mild steel ... turned out it is wrought iron. 
One observation though. A spark test should show the sparks flying without bouncing off the rest. I think it takes away from what you can see ... however I would have gotten it wrong anyway 🙂
Much that passes as idealism, is disguised hatred or disguised love of power. Bertrand Russell
 
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Mike Westbrook
For what it's worth I like to check steel on the belt sander if you have one it throws the Sparks in a straight line so you can see how colse to the floor they fizzle for lack of a better word softer steel makes bigger particles that sort of glow to the floor as it gets harder the particles are finer they stay close to the sander and burn up like a firework but as stated it's way subjective I only use it to say yup that will make a tool or nope that's that won't last honestly I've found you can tell alot by not annealing it heat it just to orange and see how it works under the hammer for the first couple hits 
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