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I Forge Iron

Carbon content needed for knives

Rich Hale

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A recent post in a thread on here warned of the lack of carbon int he steel that RR  spikes are made from. Great information.
There is a lot data on this site to fill in more details. However if you are just beginning and want to pound out a blade...And if you want that too work as a knife then you should have an idea of how much Carbon does it take to allow you to propery heat treat a blade that will do the things we expect a knife to do, wot we think a knife should do.  I like mine to cut well for a long time and not snap off if stress bends the blade a bit.. I like the shape to fit the need. and for me..I want the fit and finish to be as good aws I can make it. :; back to carbon content. anything less then .50 AKA 50 pts....is not enough for a knife blade. And you can heat treat a RR spike knife blade so it holds an edge pretty well...However you may want to do some destructive testing and see how brittle it is. As mentioned on here many times..some leaf springs are made from 5160...60 pts of carbon and there are legions of makers that use this steel,,sourced scrap,,or to really know wot you are using purchased new. Not that pricey as it can be from many places, Knife suppliers or maybe a local spring making shop as left overs,,or drops/rems....Cheap.
This  may help as a start for new makers. But it is the tip of iceberg.
More information is on this site..both in the heat treat stickies, and in the knife making lessons.

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Having been through the ABS testing (I'm a JS, working on my MS), I do have to say that it's not what I consider "real world" testing.  It's designed to demonstrate certain qualities that the ABS wants.


The rope cut demonstrates the ability to sharpen an edge to a testable standard, but not really all that useful.


The 2x4 chop demonstrates a good understanding of edge geometry, good real world stuff.


The 90 degree bend demonstrates an understanding of overall geometry and the complexities of a differential heat treat.  Over the top as a real world test.


I think that a chop test is a good one, if an edge holds up to chopping wood, it will hold up to pretty much anything a user will do to it.  I do that kind of testing even on my kitchen knives.


I think a knife should be able to withstand a drop onto a hard floor, tip down.  I call it the accidental drop test.  I'd like to see the tip survive more or less intact.


As for a bend test, I don't do one.  If you try for even 45 degrees, then you'll have to fix the blade, and you may never get straight again.  I do think a blade should flex 10 or 15 degrees under moderate hand pressure, but a 4 inch hunter isn't going to flex to a notable degree without a big force.  I don't think it's worth doing.


Anyone else got "real worlds" test to suggest?



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I saw in a book whose name escapes me, the ability to whittle or shave a curl off of a nail.  Seems like that'd be a good indication of hardness.  I do a chop test as well and also hammer the point into a 2x4, then make sure you can wiggle the point out w/o it breaking.

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This brings us to appleseed grinds vs flat or hollow ground. For woodhacking i would use an appleseed,,,For most kitchen slicing..a flat grind. .I prefer a fine edge on a hollow ground blade for skinning and cleaning game...

The beauty of handcrafted knives is we can determine the use..and taylor materials, shapes, heat treat and how we shape the sides of the blade and cuttng edge to get the most from it when complete.

I mentioned destructive testing in this thread as i suspect that aRR spike that will hold and edge will be brittle....but then again it is a short blade,,...I hate to take that chance of it breaking in use.

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A lot can be said about carbon content and edge holding.  In my humble opinion a RR spike knife is just for looks anyway, any one claiming that it makes a good knife hasn't compared it to a better knife steel.  There is a wild card in the carbon debate, alloys.  In my experience 5160 holds and edge better than 1070 even though it has less carbon, the wild card is chromium.  Alloys can take a ho-hum steel and make it a very fine material. 

Rich, your dead on about the grinds.  I do like to use a quasi apple seed (convex) grind on chef's knives.  When chopping veggies they don't tend to stick to the blade like a hollow or flat.

As far a destructive, the ultimate is to break the blade and read the grain.  If it bends, well it wasn't good material or you messed up somewhere else. 

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