Flint

[MickG]

Found a piece of flint that was picked up off the shore years back when on holiday
Told my young daughter it was a pirates finger that had turned to stone
Decided to use it to make a spark
Rubbed it fast on an old file, sparks were useless and loads of the flint was breaking off
Is the flint you use a harder flint?
Just thought I would try it
Mick

 

[littlebiglane]

I think you need to heat treat the file? There should not be a problem with your flint - maybe the technique or the angle of striking edge. Rubbing won't do it - you have to strike a glancing blow. The sparks are few and quite cool compared to a ferro rod. But pair it with some charcloth and you'll love the simplicity and the reliability of getting a spark and then an ember....

 

[JonathanD]

Might be that the flint has loads of internal fractures or it could be you should try striking instead of rubbing. Rubbing will just file the surface of the flint.

 

[Celt_Ginger]

You need a sharp edge on your flint. If you found in on a beach, it may have lost it's sharp edges. As said above, you will need to strike a glancing blow with the steel againsh the flint. The spark is created by the flint shaving off a sliver of the steel, which in turn becomes super heated and ignites, creating the spark. It may be necessary to remove the serrations from the file to achieve this.

 

[MickG]

Sorry, I should have said strike [as seen in you tube]
Heat treat the file ? is that because the file is too hard, needs a metal bar insted?

 

[phill_ue]

If it is an old file, then it should be good to go. New files can be case hardened and won't work. The flint will be the issue though, you need to get a sharp edge. Wrap the flint in a cloth and belt it with a hammer, pick a piece out of the cloth with a sharp edge and strike against that. Remember to always break/knap flint outside, if you knap inside the fine particles of flint dust can be breathed in and will cause silicosis over time and can cause your death prematurely!

 

[Longstrider]

You say that you told your young daughter it was a pirates finger that had turned to stone... Therein might be a clue to why it doesn't work..
Is it slightly conical and very round ? If so it could well be a fossil of a marine worm-like thing (can't remember their real name) rather than a decent piece of flint.
Another possibility is that it's been rolled around(bashed) in the tide for for so long that it's basically a lump of bits held together by little more than will-power, a good piece of flint shattered by the action of the sea.

You really need a nice sharp, solid, edge on a solid bit of flint big enough to hold on to whilst you strike it with the steel, or in your case with the file.
Don't use a toothed section of the file. Use the plain, un-toothed edge. The file teeth will only serve to break the flint. What you're really doing with this method is scraping a number of tiny flakes off the steel with the flint. Do it right and they're shaved off so fast that they get hot enough through friction that they burn. Yes... steel burns
The reason it works is because flint is so hard. Much harder than even the steel of a file. Hardness is allied to brittleness, hence the ability to shatter flint so easily.
If your file does not have an un-toothed edge, try grinding one edge smooth with an angle grinder, (Don't let it get too hot as this will ruin it) then try it with a good bit of flint.