Knife making question

[sumpnz]

I got that machete 5-pack the other day.  Some of them definitely look more useful than others.  Which is totally OK since I was intending to buy a few different styles in order to see what worked best for my needs and that 5 pack was easily cheap enough to justify buying it even if only 2-3 turned out to be useful as machetes.  

They are supposedly SAE 1070 carbon steel.  From my reading 1084 or 1095 would be better for knife making, but 1070 is supposedly still a good option.  Any of you ever worked with 1070?  Ideally I'd just be cutting blanks and then shaping those into knives.  The machetes appear to be around 3/16" thick, might be 1/8, might be 7/32, haven't taken a mic to them.  They have some decent spring to them, and are fairly flexible.  

What I'd like to make would be a flexible long fillet blade (suitable for halibut, tuna, salmon, etc. - probably would need to thin this one down somehow), a semi-flexible boning blade, a nice short paring blade, and if I have enough left a general purpose cooking/kitchen blade.  

For those with experience, would these machetes be useful for this, or will it just be a total waste of time?  Would I need to do some heat treating to get good performance?  What about doing some work hardening (not sure if 1070 is even work hardenable, and if so is it cold work or hot work that is needed)?  

[French G.]

No on more heat treatment, you can't (under normal circumstances) cook carbon in that isn't there. No on work hardening. Not sure if you know how the numbers work, but the 70 is .7% carbon, 84 .84% etc.

I say make the knives, worst case scenario is you learn something for cheap. Try to work with the heat treat you already have, that is grind away, but keep it cool. If you succeed you will most likely have a useful knife that is going to need an edge put on it more often, but will be easy to sharpen.

[zxcvbob]

Machetes are medium carbon steel because you hack with them, and you don't want the steel to be too brittle.  A filet knife should probably be high-carbon steel so it holds an edge longer -- you don't really have to worry about breaking it.

If I was going to make a knife, I would start with a truck leaf spring (5160 steel) or a bed frame that threw lots of sparks from a grinder (probably rerolled railroad rail), or a file.  A torsion bar leaf from an old VW is a nice size for a knife blank; I had a few pieces when I was a teenager that I intended to forge into blades but I never got a round tuit.

Forget about work-hardening.  You could do case-hardening, but better to start with higher-carbon steel to begin with rather than try to dissolve more carbon into the steel in a furnace.

[Grebnaws]

When I started grinding out blades more valuable things were ruined than a 5 pack of machetes. Sally forth and consider any losses the cost of tuition. You will probably ruin whatever heat treatment exists by using power tools if you're attempting to carve out a new blank from heat treated steel. Using hand tools you should be okay. I've never been able to make anything that didn't look like it had been dropped by an orc at Thunderdome.

[French G.]

If you have a pedestal grinder and a stone I think that best for grinding without killing the hardness. Bare hands, take a cut, dip it in water, repeat. Any sort of disc and sandpaper imparts a ton of heat.  A good belt sander with a coarse belt and a slack tank is also doable.