Tests for a good heat treat?

G

Guy Thomas

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Feb 1, 2000
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I recently heat treated a hunter made from 5160 using the triple normalize-triple quench-triple temper and I have some doubts about the knife, but they may be foundless.

After the third quench the file test seemed to be o.k., but it's hard to tell sometimes when the blade is coverd by a thin coating of scale and possibly a very thin skin of soft decarbed steel. I'm always certain of 1084 with the file test, it's always glassy hard. 5160 seems different, perhaps a bit softer after the third quench?

After sharpening, the edge survives the brass rod test fine, but after chopping into a 2x4 a bit I get a bit of wire edge curl over toward the tip that is easily stropped away and after wards doesn't get dull after additional chopping (I didn't chop it in half by any means with a 4" blade but I did do a lot of chopping)and even seems to get a little sharper after several push strokes into the pine 2x4.

However when I finished it to 600 grit the hardening line didn't pop up like I expected (like I get on 1084) but it is barely visble running in a straight line from a point about one third the length of the blade back from the tip to a point at the the ricasso about a .250" above the edge. Is a light hardening line to be expected on a triple quenched blade?

I was trying to finish this blade up to take to Batsons Bladesmithing Symposium and maybe sell, but I don't want to finish it up if the heat treat is in question. So what further test would you guys suggest? Push and/or draw cuts using manila rope? How many cuts through a material like that should a knife with good edge holding charachteristics be expected to make before dulling appreciably? If it were any other steel I'd just do the heat treat over but the triple-triple-triple deal is no casual?
 
Guy,

I haven't fooled with 5160 for a long time now, I couldn't find any good clean 5160 and got tired of the tiny inclusions popping up when mirror finishing. But, I do fool with 1095, 1084, 1080, L-6 , 52100 and several damascus blades made from 1084 & 15n20. I put a great deal of stock in the brass rod test, it will tell you if the cutting edge is tough and resilient but not to resilient, therefore making it a good edge holder. Then I chop on an old dried out oak 2x4 I have, to make sure it will take some reasonable abuse. Then I cut rope, I feel if a blade will make at least 250 cuts on a strand of 1" hemp rope (about 5/8" thick) and not need resharpening its doing what I want, I've had 52100 blades make more then 500 cuts and still cut well. I've also been known to drive a few blades through metal barrels and 1/16" plate. Then its the final test to death, the bend test, but thats just done from time to time to make sure I'm getting good grain refinement.
But for the every blade tester right after heat treating, Brass rod, chopping and cutting, if they perform those to your satisfaction, you should be good to go.

Hope this helps a little,

Bill
 
I'm in a similar boat, Guy. I just did a 5160 blade, and I heat treated it way too soft. I mostly do 1095, and did the same temper temps on the 5160, and the damned thing turned BLUE on me! I have to requench and retemper, but I was really going to triple quench anyway. My point is that you might be tempering a bit hot, and going a little cooler might serve you well. It's what I'm going to do next time.
Oz
 
Hi Guy,

I just finished my first forged blade. It is made of 5160 as well. I followed the 3 X 3 Heat treat process as well. My temper line shows up really nicely when it first comes out of the etchant but if I buff or sand, it disappears. In compairing my blade to close-up pictures of other etched blades (Ed Fowlers) my etch seems backwards in the sense that the hardened portion of the blade etches darker than the soft spine. Ed's seem to be the darkest in the transition zone. Maybe it's because of the lower carbon content of 5160 or the Hyper/hypoeutechtoid steel differences between 5160 and 52100 steel.

I also experienced the apparent softening of the steel after the third quenching cycle. Ed assured me that this is normal.

I did the edge flex test as well, and I did some rope cutting. I used 1/2" manilla rope that is fairly tightly wound. At first I got 55 cuts before it quit shaving hair. Now that it has been sharpened a couple of times, I'm up to 90 cuts. I'm pretty new to the convex edge, so maybe my increase is due to a change in my sharpening technique???

I hope someone with a lot of experience will chime in and help us both to better understand.

Rick
 
Hmmm, well I did my tempers at 350 degrees F, so I don't think that could be a problem. It's good to know to expect some softening by the third quench, I seem to remember reading that in a thread recently now that it has been mentioned. The blade has an ever so slight convex shape but the edge was put on with stones at a 20 degree angle. I think I should pick up some rope on the way home tonight and do some cuts with it. So should I try push cuts or draw cuts through the rope to test edge retention?

If it checks out o.k. it will be a close thing finishing it up by Wednesday night, if not well I've got extra time to work on the sword tsuba I wanted to finish by then also.
 
Guy,

I did my temper at 330 degrees (Coach Fowler recommendation, thanks Ed, it worked out fine). I used two oven thermometers to verify temp. When I did my cut tests on rope, I didn't have a handle on it yet. I found it much easier to do push cuts.

Rick
 
Well, I tested by chopping on a piece of oak with no damage but after resharpening and making a dozen cuts through the rope the edge shows a little wear which may be the wire edge that I initially I had trouble with. It had a fairly polished edge which I discovered doesn't cut this kind of rope very well so each cut probably put 10 cuts worth of wear on the edge due the amount of sawing back and forth I had to do. I am not comfortable with the results so far so until I can test it further or reheat treat it, it won't get a handle and be sold. I'm a little lacking in test experience and in having a large enough population of controls and test subjects.:confused:

Doing this test made me realize I have absolutely no idea how well a good edge should cut through a sisal/manila rope but I have an idea I soon will! If the portion I was cutting was still firm and twisted it sliced right through in a single push stroke, but the two sections of rope below spread out some and the sawing begins and I get nowhere and ended up cutting into the plywood also which throws the test off.

So it looks like endless hours doing push cuts and draw strokes with "toothy" edges and smooth "edges". Not until after Batson's however, yeah, I'm free. The pressures off, all I have to do is get my camping stuff together and go have a good time and learn, and I still have a couple of finished but "un"-handled knives to show. No worries!:D
 
Guy,

It sounds to me like you are on the right track. 5160 is a very good steel and very forgiving in the heat treat. It is quite normal for it to apper to soften in the third quench. I temper my 5160 blade at 325 for two hours three times. When you did the brass rod test did you draw the entire cutting edge ovrer the rod or did you deflect the edge in several spots? how many time did you do the test? Our current practice is to push down until the edge deflects then draw the entire cutting edge across the rod. We expect to be able to do this at least three times on each side of the edge. The next step, providing all went well on the brass rod test, is to sharpen the knife. You have to be sure to work the edge down past where it was bent in the brass rod test in order to get a good long lasting edge on the knife. the bending back and forth work hardens the edge and I have had it come off in a long wire during sharpening. When the knife is sharp with no wire edge then you can begin to cut rope.

We use only one stand out of 1 1/8 hemp rope for our cutting tests. you already know the reason. place your piece of rope on the cutting board holding it rather close to the end. place your blade on the rope with the riccaso in contact with the rope. now push down and draw the blade back toward your body. you sould be able to cut through the rope and use only about an inch and a half of the blade. repeat the cutting process at least one hundred aand fifty time and you can feel good about yourself and your skills as a knifemaker.
 
If you don't plan ahead like me you can try and drill part of it in what will be a covered area. If the cobalt drill bits don't work, it's probably pretty hard.
 
Bill that was a very helpful and informative post. Seeing as this is my first using knife made from 5160 I want to be sure of the heat treat. Actually it's the very first knife I ever forged about four years ago and I've never gotten back to it until now. I've mostly been fooling around with 1084 since then. I think I'll do a lot of testing with this knife and finish it up and keep it for myself. I'm confident enough of the edge for my own use but I want to see just how good it is, I'm thinking there is room for improvement. It will make a great show off knife. Every time I tell people I make knives they want to see one and I have to tell them, well I don't have any right now.

I only did the flex test on a brass rod a couple of times on each side but I had no deflection. I will definitley lower my temper temps on future knives. Hey I wonder if wrapping the rope up in cheap masking tape would keep all three strands of rope firm enough to slice through?
 
Guy,

wrapping the tape around the rope will help hold it together but some of the sticky stuff on the tape will get on the knife and mess with you. Also you ask about the temper line (hamon). I have to etch my 5160 knives before the line becomes noticeable unlike the ten series of steels where the temper line seems to jump out at you while grinding.

Testing this knife is a great way to prove to yourself what you can do. Like Bill B. above you will soon be making great knives using this steel.
 
Yeah, I kinda thought the sticky from the tape would mess things up to. Sounds like you tried this before!

I like 5160, it forges nicely and the one other knife I made from 5160 a couple of years ago with the triple-triple-triple heat treat held an edge quite well. I've been trying to stick to 1084 though just so I can develop some consistency with a single steel. However, I do have about 5 feet of 5160 stock left I've got to do something with!
 
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