Homemade hook picks

[subtlevoice]

Just finished reworking my homebrew hook pick. I used a tiny little eyeglass screwdriver (black steel end with a shiny metal handle with spinny top) and took leatherman pliers to it. Just a little bend. The metal was too soft and bent some.. I couldn't find my propane torch.... but a little colibiri butane torch lighter worked really, really well to temper it! Yeah, a lighter. It is now noticeably stiffer and responds better in the lock, I think.

[subtlevoice]

Er.. that was until I worked it wrong and bent it nearly in half.. sideways

[subtlevoice]

re-tempered the pick and it's stronger now.. also learned to be more gentle

Does re-tempering technically make it weaker? I would think re-heating would sort of rape the metal's crystalline structure... input..?

[CaptHook]

Carbon is the main element relevent to steels hardness. Heating to a nice cherry red, and quenching in oil or brine draws the carbon to the surface of the steel. Subsequent heating (tempering/annealing) draws the carbon out of the surface.
So to answer your question, yes in a way you are weakening the steel. You would normally case harden a piece of steel that did not have a high carbon content. (there are products out there for this purpose) Which infuse carbon into the surface of the steel forming a casing . There were also many different chemicals used over the years, that have been banned for use in metalworking shops by the EPA...... cyanide comes to mind.
Chuck

[raimundo]

I have used bic lighters to temper tools for a long time, also the stove works, you see, you only have to get to about 800 to a 1000 degrees to do the trick. no lighters are not that hot, but heat accumulates in metal, particularily quickly in small pieces, especially the kind of metal that does not distribute it very quickly throughout the entire piece. therefore, a one gram piece of iron wire heated on the end will be hotter than the flame heating it, especially on the surface of the wire, while copper wire will quickly transfer the heat along it to the other end of the wire and radiate the heat out of the metal along the entire length. so a heat source that will work on a very small mass of metal will temper picks nicely.

[99atlantic]

i don't think u can keep re-tempering stuff; after the first time it becomes hella brittle iuf you do it again.

just buy a butane (?sp?) torch instead of a lighter or stove or whatever. mine cost me 8.99.

[dry132]

Case hardening is different than heat treating. CaptainHook was on the right track, except for a small clarification. Heat treating the steel with a quench draws the carbon not out to the surface of the piece, but to the surface of the crystal lattice, which forms a strong type of steel known as Martensite. This makes the steel stronger, but more brittle since it's easier to shear along a crystal face. Tempering (or reheating lightly and cooling slowly) allows some of the carbon to migrate back to the center part of the crystal lattice. If you temper to an extreme, bringing the steel up to about 1600 degrees (cherry red to dull orange), then you get steel that has had all heat treatment removed, and the crystal lattice forms with the carbons internal to the crystals, called Austentite. This is a very bendable, workable steel, since the carbons are internal to the lattice and can be manipulated rather easily.

So if you want to "re-temper" your screwdriver blade, you could first heat it up with a propane torch to about 1600 degree Fahrenheit (dull orangish), then cool it slowly to form regular austentite steel. It's important to cool it slowly, because if you cool it too fast the steel will be trapped with the carbons along the shear lines. The slower you can cool it the better. Once it's cooled then bend it into the shape you want, as it will be bendy and ductile. Then heat it up to 1600 again, and this time quench it in water or oil. This traps the steel in the martensite configuration, with the carbons along the lattice lines, and makes it strong but brittle. Temper the steel by heating to about 600-800 Fahrenheit (dark bluish to purple color), and cooling slowly in air. This will create a sort of hybrid between the crystal structures which is both strong and durable, and will wear out any lock you put it up against.

I recently posted another post about heat treatment, if you search for it you might get some other ideas, too.

hope that helps!

[dry132]

<snip> You would normally case harden a piece of steel that did not have a high carbon content. (there are products out there for this purpose) Which infuse carbon into the surface of the steel forming a casing . There were also many different chemicals used over the years, that have been banned for use in metalworking shops by the EPA...... cyanide comes to mind.
Chuck

Case hardening is a little different from heat treating. For case hardening you basically heat a regular or low-carbon steel, then cool it in a high-carbon content medium. Sawdust, cyanide, or any organic material will usually suffice for the cooling pit. While the steel cools in the high-carbon material, some of the carbon assimilates into the surface of the steel. This is usually done for blade-smithing, as you get a strong sharp high-carbon edge on a sword, but a more durable lower-carbon core.

Regular heat treating of steel draws the carbon not to the surface of the piece, but to the surface of the crystal lattice. Quenching the piece traps the crystal structure into a form that is not normally stable at room temperatures, making the steel very hard and very brittle. Annealing the steel forms a bit of a compromise between the two, having both a strong hard steel, but not too brittle either.

[MrB]

but heat accumulates in metal, particularily quickly in small pieces, especially the kind of metal that does not distribute it very quickly throughout the entire piece. therefore, a one gram piece of iron wire heated on the end will be hotter than the flame heating it

I didn't notice this comment before, but it is not actually correct. One of the basic laws of thermodynamics is that heat cannot flow from a colder thing to a hotter thing. It would be like water flowing uphill. So a wire in a flame can be as hot as the flame, but never any hotter.

[dry132]

I think he was talking about heat flux through the wire, not about actual temperatures. The local heat flux through the wire can be greater than the local heat flux for the equivalent bare flame, since it acts as a sort of amplifier for the heat to flow though. It's not violating any laws of thermo, just re-distributing some heat from where the flame would otherwise be through the wire.