Do you soften your spines?

[kbaknife]

I got an email from a TG'er asking how I softened my spines.

Does my response make you think any?

"I was out working in the shop and realized I had not responded to you.
When it comes to softening spines, it really opens up a huge conversation, beginning with the merits of having a soft spine at all.
Why is it even necessary?
Somehow that seems to have just become the accepted way of doing things in some circles.
There are a lot of ways of accomplishing what you mention.
In the first place, it's only necessary to "soften" or draw back the spine if it's FULLY HARDENED IN THE FIRST PLACE!!
I simply don't go to any extremes in getting my spines fully martensitic when I harden my larger blades.
No draw back is necessary in that case.
Most people don't get their thick spines up into austenite in the first place, so no martensite is made. Their spines just revert to pearlite which does not need to be drawn back.
I like my smaller blades to be fully hardened. And tempered martensite is stronger than unhardened pearlite in the first place.
The only knives I have ever broken have been those that I intended to break anyway! And that took forces and additional tools and pipes and clamps and vises that the knife would NEVER encounter in its natural life anyway!
Just yesterday I was diddling around with a 5 inch hunter of fully hardened and tempered W1. I had it clamped in a vise at the 1/2 way point of the blade. I had on heavy welding gloves and was doing everything in my power to bend or flex that knife.
There was absolutely nothing I could do to offend that blade.
I can think of no circumstance where that knife will ever encounter stresses equal to what I just did.
Seems like people want to draw back spines and make them soft in an attempt to PROTECT themselves from having broken blades. And that is more an issue of not paying attention to standard hardening processes and controlling grain size.
Sloppy heat treating practices are not "corrected" by edge quenching and softening spines.
If a blade breaks, it's NOT because it didn't have a soft spine.
There are other issues going on.
Hope that confuses you entirely.
Just kidding.
But don't do things just because so many others do it that way."

[Bladepeek]

Well said!

[Wampus]

Al Pendray told a bunch of us at a hammer-in about 20 years ago that he thought people put too much emphasis on being able to bend a knife 90* without breaking because of the ABS test.  He said it was good to ba able to do that if you want to, but he didn't want his knives that soft of spine.  
Told the story where he and Charlie Ochs were playing around with austempering 52100 blades with low temp salts and he tried to break one of the blades with a cheater bar, pulling on it with all his might.  Pipe slipped out of his hands and flew across the shop and poked a hole in the wall, blade had no damage or permanent bend in it.
They did eventually break it with a longer pipe, but it took a lot more force than it would have taken to bend a spine-softened knife to 90*.

[kbaknife]

Keep in mind that the ABS performance test is NOT!!!! meant to demonstrate the "proper" way to heat treat a blade.
That misconception will never die for some reason.
That test is to demonstrate the makers ability to CONTROL his heat treating practices and to put different structures of steel WHERE HE WANTS IT!
It is NOT designed to show the correct way to make a blade.
If a maker IS in control of those conditions, the only way to demonstrate it is by destroying the blade by performing those tests.
I can't believe even Al Pendray didn't know that.

[Lin Rhea]

This is something I have been drawing attention to as I get the opportunity. I also recieved an email on this subject which I was about to answer when I saw this thread.

I have seen competition knives bend and take set while chopping a 2 X 4. This is no doubt because the maker drew the spine down to dead soft as if it were a test knife.
   
I want my knife's spine to be somewhat drawn back, thus softer than the edge, changing gradually from edge to spine while at the same time drawing even more from the ricasso and tang, but in a smooth, blending progression, not in sharp zones. I can tell that the blades have more "life" in them. However, this is far from dead soft. The steels that most of us use are spring steels, so basically what we make is a spring with a hardened area to hold an edge. I like to get all I can out that steel and use it to make just that.

In a similar way that a bow's limbs energy should be distributed throughout the whole length, a blade never has more stres in any given point than it can stand.

[kbaknife]

And I forgot to mention, it seems that whenever people erroneously equate the Performance test with simply making a knife that will bend 90 degrees without breaking, they seem to forget to mention that the knife must also shave, cut and chop repeatedly without the cutting edge dulling, rolling or chipping.
There is ssssssssoooooooooooooo much to making a knife what it should be that it is not at all confusing that there are volumes of books and magazines and classes and 100s and 100s of years of culture behind the subject, as well as unending volumes of information regarding the topic.
It's just not accomplished in a weekend with a charcoal fire and a torch.
The question "Do you soften your spine?" should only be asked if you're really ready for the answer.    :eek:

[srtben]

Well put Karl and Lin!

[tippit]

Since I don't seem to edge quench that much anymore, I will soften the tang especially when I don't drill enough pin holes...no need for carbide drills.  Jason Knight showed me a quick and easy way to do that by protecting the blade in wet sand and running color down it with a torch...tippit

[kbaknife]

Jeff, I made a holder that suspends my blade in a tube of water if I need to soften a tang. But that only happens if I'm using 5160, 52100 or Cru-V, all of which will air harden after soaking in a heat treat oven.
Other than those steels, if the tangs don't hit the quench on blades where we're using our forges for austenizing, there's no need to draw them back. They're not hard.

[tippit]

Karl,
I'm using mostly 5160, files, and occasionally old springs when I find them which are probably 5160.  My tangs come out too hard to drill if I need to add a handle in the future.  Hard tangs aren't a problem with para-cord though.

By using wet sand, I can modify/mold the sand so just what I want to remove temper is exposed...either a portion of the tang or the entire tang up into the spine.

[kbaknife]

It's amazing the amount of things sand can help with.
Cool "trick", Jeff.
Jason can be handy to have around every now and then.

[amar911]

It's great what can be learned from you guys. Thanks again for the lessons you teach steel dummies like me!!

Allan