Cheap, good quality Shuriken throwing star

Step 8 Sharpening

This step is semi-optional, but I would recommend it. Now that your sides are flat, use the grinder (or a file) and grind edges onto the star. They should be at about a 45 degree angle. When you finish grinding an edge with the grinder, quench it in some water and slosh it around to cool it off (its SUPER hot).

Comments

[Otaconmgs]

The reason it gets discolored is because it's tempered metal. The discoloration indicates the temper being taken out of the metal, causing it to be brittle, and more easily chipped.

[Andyman3k]

Actually, I thought that the softer a metal is, the less likely is is to break but more likely to dent and bend. Its the really HARD steels that are more subject to cracking and fractures. Also, ALL steels will discolor if heated, even the non tempering and non carbon steels. Temper only relates to a metal losing hardness, but this metal was never hard to begin with. I think the discoloration might have something to do with rapid oxidization during heating.

[ninja of suburbia]

your'e both right.   the softer a metal is the easier it is to deform.  the harder it is, the more likely it will break.  All commercial metals are hardened and tempered. The discoloration is due not only to losing its temper, but impurities in the metal coming to the surface.  Or, if the metal turned a really dark blue, congrats! you just tempered the metal as far as it will go.  btw, metals only change color if they are heated really hot, like with a blow torch. as for oxidization, it depends on the metal. personally i doubt it, seeing as you would have to get a very low grade steel or high grade iron, which is not made very much anymore.  props for the ninja stars, though!  fyi, plasma cams are easier, if you can get ahold of one.

[K.hall86]

in order to nip this whole issue in the butt...just constantly cool the metal in a water bin as you work. In doing this, the grain structure of the material will stay in tact and keep you from altering the properties of the metals..

as a note, when you super heat the metal...(lets just say anything too hot to handle with with thin gloves or bare hands) if the metal is dunked into a water bath (quenched) it has become much harder...in a cool natural state, the molecules of the metal are in a Body Centered Cubic (BCC) pattern, which is very structurally stable. when heated, the molecules transform into Face Centered Cubic (FCC)...if allowed to cool slowly over time, the material will return to its original structure, if quenched the molecules will the shape of the Body Centered Tetragonal (BCT)...this is where the weakness comes from...the larger molecular structure adds hardness, and like you mentioned brittleness...if you want to fix this all you have to do is heat the metal up and allow it to cool slowly over time...this is called annealing

yet another note...you are using galvanized steel...who cares?? if you had cobalt tool steel, then you worry about heat effects on the metal...other wise, it was a good instructable, and keep having fun!

[ninja of suburbia]

that is one way to soften the metal, you are right, but tempering the steel will also return the metal to a more stable pattern, with the benefit that,by watching the colors in the polished metal, you can get it very precisely softened, depending on the task at hand, for example a very light temper on a chisel, but a deeper temper on a knife

[scottmiller]

 Cool. I've made several shuriken and I've found that a good way to make it sharper even faster is to put it on something and just hammer it. The hammering makes it thinner, but not noticeably bigger (The metal spreads out making it slightly bigger). It really helps to do that, especially if you're like me and don't have a grinder. Nice instructable.

[pearldrummer]

buffer*

[pearldrummer]

you should take the circular file and file down the drill marks and you should also ge a bffer weel and shine it then it would look pro

[krisking93]

niiiiiiice