OK everyone, my turn to ask an opinion type question. How many out there fully harden their blades, and then accomplish a soft back draw? A couple of recent events have me doubting this methodology, and I would like to hear what your thoughts are on it.
Have you experienced any problems with blades that have been treated in this manner? What are your thoughts on what takes place in the steel when the soft back draw is accomplished?
Please explain how you go about completing the soft back draw in your shop. I'm attempting to form some theories and what to compare different methods.

Ed,I do this on my O-1 and 1095 blades.I slowly bring the blade up to nonmagnetic,then quench in olive oil.My draw is done by you a propane torch to keep the heat down to a managable level,then start heating the butt and back of the blade keeping the edge down and away from the heat.I heat until the back and tang are bluish and as the heat travels up the blade watching the edge area,I look for a light gold color on the edge,then quench in room temperature water.I make mostly smaller utility and small hunters under 6" blade lengths.I have had positive feedback from my customers,and my EDC is done this way.It may not be the most precise but seems to work well.I think I know what you have found and that may be blade breakage,but I have not encountered this yet.I think what happens to the steel is that you have a tight grain near the edge and a looser grain behind that creating a line down the middle of your blade.Don't know for sure,not a metallurgist,just a mechanic.Hope this helps,Dave

I do this on most of my blades, as size allows; although I have started using an edge quench technique lately on larger blades. I feel like the simpler, higher carbon steels, like 1095, probably gain a great deal of over all blade toughness from an edge quench. On steels with lesser carbon, I feel like the soft back draw is just as good. I cant point to lab quality tests, just over all observations. To do the back draw I first harden the entire blade, except for the tang. I oven temper for the edge as appropriate; then I draw the tang, deeply, as a separate step, allowing the color to run a little into the blade. This usually is in the choil so you dont soften the edge. But Id rather have a soft corner on the extreme rear of the edge than any risk of hardness & brittleness at the tang/ricasso juncture. I draw the back next with a common propane torch, standing the blade in a tray of water to avoid over heating the edge. I never quench the blade to cool it after I get it hot. Sometines it takes a while to get the back soft. I try to take it through blue to grey; dead soft in other words, at the extreme spine. I feel like that using the propane torch that it is not as deep a draw as you might believe from the color. Testing with files indicates that that this all works, and I have seen excellent toughness and springyness from blades so treated.

Ed , about 8 years ago at a Calif. Blacksmith Assoc. event I did a cut and bend demo. The young guys were imprested that it didn't break. But the old smiths laughed becaused it didn't return straight and it so easily bent over. Most comments were that I took the lazy way to harden the blade. Since then I fully harden the blade ( except for clay hardening to get a hamon ). I do pretty much what the other guys do on the spine. I could pass my journeyman cut and bend test now, but I'm still experimenting to get it to return straight.

Ed in my experiments with doing a spine drawback it never fully softened the spine to pass a 90 degree bend. I tried it with a torch while holding the edge in water and using the electric burners on the stove. I personally believe that by doing an edge quench you can fully control the amount of hard and soft steel in the width of the blade. A comparison of why I dont think it always softens the spine is in relation to tempering times. I mean just to fully convert the structure of the steel we do multiple tempering at 2 hrs each so I think to do a drawback successfully it must be done multiple times and for a length of time. Just my two cents. I truly believe that everyones techniques and shops are different and as usual what works for some doesnt work for all.

I soft back draw 5160 & 52100 heated in a gas forge and edge quenced. doesn't seem nessary if heated with a torch or edge down in a coal forge. The spine gets more heat in a gas forge and will air harden above the oil level, [super fast normalize on the spine even though it is only at the beginning of critical temp.]. I fold a wet towel and put it in a large vise , I put the hard edge in the towel and use metal spring clips to secure the towel to the blade edge or curves sticking out of the vise. I blue app 3/8" down the spine and the tang-ricasso juntion using an oxy-acetylene torch. 1-3 times, 1 time seems to work. I have air hardened spots when in too big a hurry. Do it in low light and slow. Propane hand torch did not work as well for me as the oxy-acetylene does. the blades broken ,for a look see, after a soft back draw showed a larger grain size in the area drawn to a blue color.
Hope this helps
B L Howard Long hunter Forge

Mississippi Long Hunter I like your way of thinking about things. I appreciate you sharing your experience. I am surprised no more folks have posted on this topic. Maybe it aint too exciting enough. I have aimed to make some drawing "tong' with blocks to heat in the forge. Tim Lively I believe has pictured these, but like so many things havent got around to it. always figured a oxy-acetelene would work better than a propane torch .

Ed,Ok we want to know what your poll did and what problems you had so we don't have the same.Hope we helped,Dave

The whole reason for the poll was the fact that I have had two individuals test for their JS ratings in the last couple of months and both of their blades broke during the 90-degree bend test. Both also told me that they had soft back drawn their blades with oxy/acty torches. The most recent one left the temper colors on the blade, and visually it was a nice, even, medium blue for the upper 2/3 of the blade. Upon failing (breaking) I inspected the blades and both showed a fine, even grain about ten thousandths down into the blade on all sides. Sort of like a fine grained sheath around the interior of the blade. Beyond this fine grain however, was a very different story. The grain was LARGE, and VERY course. I did a bit of experimenting with a piece of the broken blade and found that a small chisel, with a few light taps would dent the surface, but once past that ten thousandths "sheath", the steel broke easily. My conclusion is that the soft back draw does not penetrate the blade enough to convert the entire thickness, and therefore is not a suitable method for passing the test.
In another thread I believe I found the answer. A torch, regardless of what type, heats by convection, which is a very inefficient way of tranfering heat. Whereas if a person were to accomplish the soft back draw using a heated bar of steel/iron, that the blade is in contact with, the heat would be transferred via conduction, which is a very efficient and through way of heat transfer.
I still will not recommend the soft back draw to those who are testing for their JS or MS ratings, but if someone insists on using this method, I will recommend a hot bar of steel/iron versus the torch.
The reason I asked opinions is that I do not use a soft back draw on any blades I produce, and haven't for several years. I was having similar problems, but solved them by going with the edge hardening method and was curious to hear if others had experienced similar difficulties. This has also promted me to write another article for my web site, which will explain how I recommend a blade be produced to pass the ABS tests. Hopefully it will be there sometime next week.
Thanks to all who responded and helped with this situation.

I've enjoyed this thread, as well as the previous one we did on heat treating 1095. We're talking about the most enjoyable and fascinating part of knifemaking for me, which is heat treating.

I'd like to continue these types of discussions in other threads as well, with everyone sharing their various methods, experiments and results.

Good thread. I'll look forward to your new article Ed. We need to remember to get dogman to include it in the CKD Reference and Tutorials section.

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I just joined the ABS so Im very interested in all the testing. I quench my blades fully instead of edge quenching becuase I think its stronger under normal circumstances. For the ABS test I imagine that the edge quench would be better. In the field a knife will never be bent to 90 degrees so the edge quench isnt needed. My tests showed me that I could bend a bowie in a vise by hand (without a pipe on the handle) that was edge quenched and it wouldnt return to true. The fully quenched blades are too strong for me to bend them by hand enough to where they dont return true. So for knives I make to sell I use the full quench and then selectively temper the back using tempering tongs like this;
http://www.photoloft.com/view/exportImage.asp?s=xpag&i=1880068&w=360&h=240

Tim,
You've got the right idea! One of the things I always hear potential JS and MS folks say is that they are concerned someone will think their test blade is "whimpy". WHO CARES!? The ABS tests are to prove three things.......
1. Can the individual produce a blade with good edge geometry?

2. Does the individual know how to heat treat their blades to achieve a desired outcome?

3. Does the individual understand (and know how to apply) all the facets that create a good using blade?

The basic prinicples, applied in the ABS guidelines for testing are to have edge retention, durability, and toughness. No where does it say that a blade must return to true after the bend.
Don't get me wrong, I'm not railing on you, it's just that so many folks are concerned that if a test blade does not return to at least near normal, it's a bad thing. Not so.
For example, I created a test a damascus test blade, and only hardened about 1/4" or the edge. The blade passed all the ABS MS tests, but when it came to the 90-degree bend, I did it with my bare hands! Of course the blade was "wimpy", but it passed all the tests, according to the standard. I guess what I'm saying is that the ABS tests are a case of making a specific blade, to accomplish certain things. This in itself is a testiment to an individuals understanding of bladesmithing, and his/her abilities to manipulate the media.

Very good topic and discussion. Many people are under the assumption that a blade that passes the ABS ratings test is a perfectly made blade. Not so, it only shows that you have CONTROL over your medium, in this case steel. If you have the ability to make it perform correctly for these tests, you can also make it perform other specific functions as well. I do think that most guys starting out don't draw the backs long enough and or hot enough to convert the structure. We have to remember that they are called TIME/temp curves. Many Journeyman blades passed the tests over the years using a drawn back blade, so it is a workable method. Ed, sometimes I wonder if edge quenching allows folks to get away with coarser grain structure in the bend tests, as it is very soft backed. The drawn back won't work very well with anything but a fine grain structure, IMHO. Nobody had discussed grain growth with me till my first JS test blade snapped, I would have bet a hundred bucks that it wouldn't have. Those kinds of things tend to make you focus, know what I mean? nice thread mike

Ed,

I might be completely mistaken, and please set me straight if I am, but if the above torch-drawn blades that cracked upon testing had a -medium- blue color wouldn't that indicate that they were not fully drawn? i.e. they were still in the springy range and not in the -dull- blue ( almost grey ) annealed range?

Jloose,
You are correct........ on the surface, the surface of the blade that is. What is occurring with the blades that have been drawn via a torch is that the conversion of the steel is not completely taking place due to the poor transfer of heat via convection. (at least in the case of the two blades I mentioned).
These folks were under the assumption that med to light blue was what they were suppose to do. It was simply a lack of experience and experimentation on their parts. This is typical of a lot of "newer" bladesmiths. Most will do a lot of reading, and take that as gospel. Then, once they realize that what the books say does not always work, their next step is to start asking some of the more expierenced folks questions, and then finally, once they realize that there is no single method that is fool proof, they start experimenting on their own. It happens to some more quickly than others, but there are always those who say......... "Well.........That's how the book said to do it!"
Here's a point to ponder............ If a person fully hardens a blade, and then does a soft back draw until the spine is sky blue, or slate gray, what was the point of fully hardening the blade in the first place? Seems to me that would create much more room for error than just edge quenching, not to mention all the extra labor and time involved to do it correctly. If the blade has been handled properly to this point, the grain is extra fine and ductility is at or near optimum, why risk messing that up, just to do a soft back draw when so much more can be accomplished by edge quenching? It might be 6 of one and 1/2 doz. of another, but by utilizing various depths of quench you can control the stiffness, or lack thereof of the finished blade without risking the thermal shock and possible crystalization that occurs when you torch the spine of a blade and then quench it, as a lot of people do using the soft back draw method.

Hey this is getting good!

My reasoning for the fully quenched blade with a tempered back is becuase I want the blade stiffer than a back will give that hasnt been fully hardened first. I dont take my backs to dull grey. Only to spring blue. Yes they will break if you put a pipe on the end of the tang and bend them 90 degrees but they wont under normal human power. No way. I can do damage to one using only human power that has been edge quenched. I cant break it but I can bend it so much that it doesnt return to true. To me the stiffer blade is superior in the field becuase it wont bend that far. Theres no way you can break one them with your bare hands while using it. I understand the edge quench use for the ABS test but not for real life. Its too wimpy becuase it bends too easily. :)

O.K.,

Glad I had my facts straight... every now and then I think I have something basic down and one little thing throws a wrench in the matter... Also glad I'm not the only one to go through the book / asking around / experimenting! I feel much better about frustration with books and all the dumb questions I ever asked... ( no dumb questions... right? )

One thing that Ed brings up is actually something I've been pondering for some time. One reason I can think of to harden a whole blade and then draw back is this: if you have a damascus blade ( especially of the high / low carbon variety...) and you wish to etch it -evenly- I have a theory that hardening the whole blade, evenly tempering, etching, -then- drawing back will accomplish this. I haven't tried it yet, but have a couple nice bowies in the works... I don't usually draw back on my blades because in theory I have harder and softer layers with 1020 / 1095 already.

I say theory because that's a whole 'nuther thread... suffice it to say I think that there is a significant amount of carbon migration occuring with my damascus but I still notice a difference in the hardness of the layers. One thing I've wondered is if the manganese makes this difference in spite of the relatively even carbon.

I would have to agree with Lively that another reason is so you can keep your back temper options open as far as making the spine more springy.

One more random thought - It seems to me that the ABS test is more about demonstrating control of the material rather than making the absolute best blade for use. After all, you have to destroy the thing to pass the test...