Blade testing

G

Guy Thomas

Joined
Feb 1, 2000
Messages
1,370
I've been testing a knife I forged from 3/16" x 3/4" 1084 and while I'm pleased with it's performance I don't have much information to compare it to in order to decide whether my heat treating is on the money or not.

The knife has a blade of about 4" with a strong convex grind. It was normalized three times after forging and then annealed once. After grinding I normalized three more times and quenched once in Goddard's Goop. I then tempered it at 415 degrees three times for 1 hour each time. It has chopped through a 2x4, including several pine knots, twice and suffered only slight dulling toward the tip. With a knife this small it took several hundred strokes to chop up the 2x4, so would the dulling be considered normal? (It still is capable of shaving after just stropping on leather glued to a board with a little buffing compound on it.)

The knife has been dropped tip first into a concrete block half a dozen times from a height of 33" with no damage whatsoever. Tonight I dropped it from a height of 4' onto hard seasoned patio concrete and the tip did dull for about 3/16" and chipped slightly. Again, I have no idea if that damage is reasonable or not. When do you decide your test has exceeded what a knife should reasonably be able to survive?

Lastly I have thrown this knife repeatedly into a 2x4 sinking the tip an inch into the wood and have pried it to the side. The blade flexes slightly and pries out a chunk of pine with no problem.

All in all while I think my heat treating is on the right track, should I be concerned that the blade dulled at all while chopping up the 2x4 or that the tip suffered minor damage after being dropped from 4' into really hard concrete? Should there have been no damage after these tests?

I'd really like to hear your ideas on this and I'll try and get a picture of this knife up soon. It's the first knife I've put a makers mark on and it came out pretty neat. I used a resist of asphaltum/beeswax and dilluted ferric chloride to get a great etch of my initials.
 
Guy It sounds like you are definetly on the right track with your heat-treating. Im not too impressed with the geometry of the knife...what I mean is the blade is 3/16" thick and only 3/4" wide. I think you need to draw it out longer, thinner and wider and tapered. It should be normalized 3 times and annealed at least once, quenched once and tempered 3 times at about 405-415 deg. Some ovens are not accurate. After the heat-treat finsh the grinding to final size. I think it should shave after the chopping without stropping (ABS Journeyman) I have never done the concrete test but knives are not made to cut concrete so dont worry about the damage. It great to see you test your knives.
 
Hey Bruce, the 3/16" x 3/4" was the starting stock size. The finished blade is a little over an inch wide and a little over 1/8" thick with a slight distal taper. The slight dulling during the 2x4 chopping was limited to about an inch and a half from the tip so I'm wondering if I didn't overheat the tip slightly during the quench, but unlike a larger test blade which might go through a 2x4 in a couple dozen stokes this blade literally was chopping into the pine for hundreds of strokes. Thanks for the input!
 
Here is a hastily made and horrible picture of the blade of this knife. Please bear in mind that this knife was made mostly for testing and I intend to break the blade eventually. Still I might clean the handle and blade up some more and put a decent Turk's head and handle wrap on it. It's hard to intentionally break even a gnarly looking knife!
 
Guy, It looks nice for a test blade. OK I think you have a winner there. 3/16ths was just too thick for a good test with a blade that short. You are right about the 10" bowie test blade can slice through a 2x4 in seconds. Also after the chopping the blade will still shave but there is alot more cutting edge length to chop with. I use every inch of it to raise my chances of passing the shave test.

I agree you may have overheated the tip while forging and no amount of good heat-treat will repair it. Good lesson. Now go bend it. :eek:
 
Guy it sounds to me like you definately are on the right track. Now I feel like making something to test with myself! I've never pushed any of my knives this far so have no idea how they'd measure up, but my sense is they wouldn't hold up this well. You also are keeping good records of your method, which will help us all. Please keep us posted!

By the way, I dig your mark, the resist worked perfectly! Did you draw on the knife through the resist or use a pattern of some kind?

Dave
 
Bruce, thanks for the insights. I know you must have gone over this any number of times getting ready for your Journeyman testing! Testing is fun, if a bit disapointing at times. I think I need to aim for the edge that holds up to the 2x4 with absolutely no dulling. I actually managed this, don't ask me how, with the first knife I made from some saw blade steel (L6 maybe?). I think I need to make bigger blades! :D

Dave, the design is literally cut into the resist using a burin of some sort (in my case a heavy tapestry needle) and free hand drawing technique. You can see this in David Boye's book "Step-By-Step Knifemaking" in the chapter near the end that showcases Francine Martin's etched scenes on his knives. The asphaltum/beeswax resist is hard and brittle at room temp but becomes soft and pliable when heated under a 100 watt bulb. Designs are easily cut through a thin layer of the resist. This is a cheap way of etching logos with an artistic flare but the downside is it's a little time consuming and messy. (Not to mention a little nerve wracking, a magnifying lens of some sort is a big help.)
 
Silent,
Look up Wayne Goddard's brass rod test. If it is hardened and annealed correctly you can see a flex in the edge and it returnes to center without chips.
Can you help me find asphaltum? None of the local art supplies stores can even order it.
Thanks, Lynn
 
Hey Lynn, thanks for reminding me of the brass rod test, I keep forgetting about it.

After exhuastive searching on the net for asphaltum with no luck, it occured to me I was searching for too specific an item. I found a cheap source of powdered asphaltum on my first try when I searched under printing supplies. I bought 2 lbs. of powdered asphaltum from Renaissance Graphic Arts, Inc.

http://www.printmaking-materials.com/

I can't remember quite where I found it on their page but I think it was under Lithography Supply.
 
I did the 2x4 test, then shaved hair with it. The blade looked good until I looked at it with a strong magnifying glass. I could see 1 or 2 very small chips in the blade. You could not see these with the naked eye. Do I need to raise my tempering temp.
 
One easy and sure way to find micro chips, etc. in the edge of your blades after chopping or other impact tests is to run the back of your fingernail along the edge. You will be able to feel any micro chips immediately.

As far as testing for the ABS goes, whether you will fail or not for such invisible, but palpable, edge deformations seems to be up to the discretion of the master smith administering the test. It was made very clear to me by JD Smith that I would be failed for any and all sorts of edge deformation, whether visible or not.

John
 
Silent,
Well, although my methods a very different and I use 1045, I can offer a description of some typical testing I do. It may not hold any merit because we're not doing things the same, but at least you have some info. :cool:
When I set out to abuse I knife I do just that, I never intend for the knife to survive. I destroy it. It's extreme point of failure is how I judge my work. And I have to remember its not exactly a lab environment, so results are an average and I'm always testing different sizes. I also work with fully convex ground blades. I do so with most between 3/16" and 5/16" thick spine. Width varies from an inch to inch and a quarter, but testing results are very simlilar. Except, its a pain in the ass to bend one of those thick ones, even with the aid of a bar.
For cutting, I judge the edge hardness and quality by how it sharpens on the grinder. Then I strop it. I only test blades that are very sharp. It only makes sense to me. Then I hack up some steel plumbing pipe. I cannot chip the edge with my bare hands alone. I get a tiny dull spot after 10 to twenty chops. The broader edges naturally do better (at steel) and really bite deep into the pipe. Rarely, I get some slight deformation on the edge, but that usually does not happen until I grab a four pound drilling hammer, I use at the anvil from time to time, and strike the knife into the steel at the spine. Eventually, after some seriously hard blows I get some edge deformation with some very tiny chippage on occasion.
Sometimes I flex the blades in a vise. I do not use boards or round the edges of the jaws. Their accute. My blades (usually 5 to 8 inch blades) are diff hard and fully tempered. Edges and full hard blades will snap at about 45° and the bodies will usually crack around 90°. Sometimes I have to wiggle the steel back and forth to snap it clean though. :cool: I use to have my blades wrap around the vise, but now I prefer a harder body than most diff hard blades. The blades won't break, thrown flat or tip first and as hard I can to the cement several times. Its extreme and kinda funny :D I cringe a lot too, but it shows me the full scope of their limitations and ways to improve in more PRACTICAL areas. he he he
All my 1045 stuff is classical Japanese design by the way. And I hand forge from 3/8 to 5/8 inch round bar stock (usually). Well there's my long winded input. :D

-Jason
 
Epsilon, now that's what I call extream testing!

One test I havnt' heard anyone else use is the bone chop test. On my small hunters I try for as thin an edge profile as I can get, and still not deform or chip out. A lot of people use 2x4"s, and often whack into hard knots to see if the edge will hold up. This works great and I do this too, but I have added one thing to it. I have an old dry cow leg bone that I like to hew on with every hunter I make. Now I don't try to cut the bone in two, just chip out some of the bone and work the whole edge. If the knife has passed the brass rod test and cutting and 2x4" test I thicken the edge a little and re-test till it passes.

Not real scientific, but it lets me know just how thin I can get and still be a good worker.

For big knives I like to chop on hard woods, oak, hickory, gum, whatevers laying around.
 
Wow, I see I have some serious testing to do. I realize that I just haven't made enough knives for the explicit purpose of testing them at different tempering temps, etc. I will try and include a test knife every time I do any heat treating and keep notes. If I could raise the performance of the steels that I want to work with the most (1084, L6 and 5160) to the level Jason gets from his 1045 heat treats (clay coated I presume?) I'd be a happy man indeed!

Jason, you mentioned throwing them tip first into concrete without breaking the blades but did the tips suffer damage from that abuse? (i.e. blunting the tip, damaging the edge near the tip, etc.)
 
Wilkins,
No problems getting the 1045 to properly harden. 1045 can max out at 62HRC (as quenched), if austenitized from 1550°F. That is still within fine grain range too and the example most often seen on I-T diagrams. But, I don't austenitize that high. Tempering 1045 was the real trick. Was a delicate act.

Silent,
Of course the tips blunted a bit! I am only human. He he he :cool: But it depends on the knife. Thinner tips (like one suitable for skinning) were more prone to chipping slightly, thicker ones (like 1/4" spine tanto) just got a little dull. I like very sharp tips too. We're talking like maximum damage 1/16" gone. Bends are rare, if they don't snap, they usually just get a little dull. Most of the tips on the tanto I make stay in tack and dull a little, chipping it very rare.
Keep working man. Its taken me four years of research and practice to get this far. I can't count how many blades have been destroyed. :confused: Eeee. But all for the sake of CONSISTANT performance. However, in my book, your testing is sufficient for a plenty good knife. The tests I was doing is for tanto performance, not utility.

-Jason
 
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