Questions for the knife makers.

[Bagman]

Picked up a unknown circular saw blade. About 20 inches. It is a single blade...unlike the carbide tipped multi part air quenched ones I'm use to.

It skips a file along the diameter. So it's hardened. Guessing it's a high carbon steel based on that.

How should I proceed in testing...before using the material? New ground for me...

 

[Black Hand]

Quick and dirty... https://en.wikipedia.org/wiki/Spark_testing

 

[Bagman]

Hoping for real hands on experience working with unknown materials.

Thanks in advance for sharing your own actual 1st person experiences/results.... and sharing your attempts with saw blades.

 

[Black Hand]

I've made several knives from circular saw blades and you should first determine if they are high-carbon (spark test). If not high-carbon, move on. If yes, then a heat-treatment is likely possible. However, the exact composition of said blades isn't possible to determine in a garage workshop, so going with available information as to what steels are primarily used might give you a OK idea if a heat treatment is possible. You could always do a quench and see if the file-test indicates a hardenable steel. Breaking hardened pieces will also show you the crystal structure. All that said, working with unknown steels is always a gamble.

As to the rest, perhaps you should ask a more specific question...

 

[pondoro]

You're going to have to remove the teeth anyway - so plenty of territory for spark testing, or cut a few teeth off and test various heat treating recipes.

Aircraft engine forgings for critical parts have samples removed for testing material properties to ensure the melt/forging/heat treat process produced the right properties.

You've got your samples in the teeth.

 

[LRB]

Just buy a known steel. Then you know what you have. Good steel is cheap enough.

 

[Bagman]

Thanks guys. Great suggestions. I will do a spark test later today. If that looks good I will cut out a small knife and use the stock removal method. Will keep it cool in the process and not loose it's hardness.

 

[Bagman]

Wick..

I think I've been watching to much Forged in Fire .... :grin:

 

[Artificer]

Maybe so. Remember how many of the blades they made from different steels from different sources, that turned out cracked or would not harden well in the show? If anything, that is more evidence to follow Wick's suggestion to begin with a steel you know; so you can forge, harden and anneal it properly.

Gus

 

[Bagman]

Here's the method I will use...
https://www.google.com/url?sa=t&so...CCkwAw&usg=AFQjCNEV6gtwh5h-dgCyRzO06gRBo-zhnw

 

[Black Hand]

If that looks good I will cut out a small knife and use the stock removal method. Will keep it cool in the process and not loose it's hardness.

You may find this difficult. If you are cutting a blank from the blade, the steel is either soft enough to cut, in which case you would need to harden OR you will need to use cutting discs, in which case you will generate enough heat to burn the temper (unless you cut the piece far larger and remove the burnt parts). If you had a blade you could profile (e.g. a planer blade), then stock removal while keeping everything cool is possible, though still a considerable investment in time.

In either case, a heat treatment isn't all that difficult to do, though it requires equipment and basic knowledge. A small coffee/paint can forge ( Coffee can forge ), torch (with a Rose tip) or pile of charcoal (with some sort of blower) can be used to heat the steel.

Wick's suggestion to purchase steel is excellent, but you'd still need to heat-treat in most/all cases.

 

[Artificer]

Here's the method I will use...
https://www.google.com/url?sa=t&so...sg=AFQjCNEV6gtwh5h-dgCyRzO06gRBo-zhnw[/quote]

Am I missing something? It looked like he was comparing the sparks from hardened files against unhardened steel?

Gus

 

[Bo T]

Never made a knife from a circular saw blade. But the teeth will probably be much harder than the interior part of the blade. This is so most of the blade will be tougher and less likely to break. Unless the edge of your knife blade is along the teeth part of the circular saw blade, your edge will be soft. You can make a usable knife but you will need to sharpen it more often.
IMO the best way to test your steel is to cut out a slice. Heat to bright cherry red and immediately quench in water. If the steel breaks easily-sort of like glass (I've done this) it will harden and has the potential of making a good blade. To make a good blade you will need to heat treat.

 

[Bagman]

Gus...

He was showing how various steels spark. Mild steel (low carbon) up to 01 and 02. It was interesting seeing how poorly the 2 knife steels sparked.

 

[Artificer]

Except the knife steels sure looked like unhardened rod, while the files had been hardened, so of course they gave off larger sparks? Or did I miss something? I'm going to watch it again.

Think of a frizzen that is not hardened at all or not case hardened or hardened correctly. No sparks if not hardened and very few sparks if not hardened correctly.

Gus

 

[Black Hand]

One should look at the complexity of the sparks.

 

[Zonie]

IMO, the hardness of the steel has little or nothing to do with the type of sparks the steel will make.

A dead soft high carbon steel will make exactly the same kind of sparks it makes when it is fully hardened.

The thing we should be looking at when we do a grinder test on steel is the way the sparks "explode" at the end of their flight.

The quantity of sparks from a piece of annealed high carbon steel will actually be greater than from a piece of the same material that is fully hardened.
The reason for this is, a greater quantity of the soft steel will be removed by the grinding wheel or flint hitting it.

In the case of a flintlock, if the frizzen is too soft, the flint will dig into the surface deeper.
This increased depth will slow down the speed of the flint rapidly which produces cooler sparks.
The pieces of the steel that are removed are also thicker so they are less likely to "ignite" in the "flash" that speeds up the pan powder ignition.

 

[rich pierce]

It's almost certainly high speed steel and devilish to anneal and re-harden and heat treat. Unless it's a truly ancient buzz saw blade. Those are usually about 3' in diameter and old ones are carbon steel.

 

[Bagman]

Rich...

It's a early blade that's a 30 inch diameter. It sparked great. I'm going to make a small knife out of it this weekend. I have a 2 burner gas Forge and will run through the entire process thru to hardening.

 

[omarick1948]

I think that Wick's suggestion is still the way to go!