need advice

[Scott Roush]

Hi there... two things that are dragging me down lately:

Grinding... How far down do most of the experienced folks grind before heat treating (for a flat grind)?  I've read a lot about how much to leave right at the edge... but you can have a 1/8 edge and still have a lot of grinding to do to get a working flat-ground edge. I find that if I leave, say, an 1/8 on the edge and then harden... then it takes me forever to grind the rest of the way down for a true flat grind.  Especially with the hard steel and trying to keep temps down along the edge.  I always end up having to put in a bigger secondary bevel than I want... Or is it just the impatience of 'Grasshopper'?

Hamon - Anybody here try clay quenching 1084 for a hamon? I know that 1084 isn't the best steel for it, but I've seen nice hamons posted elsewhere with it.  I've done a couple and have NO sign of differential hardening.  I understand that you have to experiment... but is there any one variable over another that is best to play with? I quench in brine and use APG #36 (from Ellis).

Thanks a lot folks....

[Lin Rhea]

Scott,
         You can grind a little thinner before quench if you want. I like mine about 1/16 inch thick, even thinner on small knives. I radius my cutting edge and make the grind marks run parallel with the blade so as not to introduce stress risers. All of this really is dependant on your quench temps and the control you have.

       I use my oil and am not familiar with the oil you mentioned, so I wont go there. However 1084 is great steel and will give a fine hamon. Lin

[bigbadjon]

I think you could take the edge down to 1/16". We take them down to about that and have very few cases of warpage. I do not know what equipment you are using but some maker do not grind until after the heat treat so it should not be thst much more difficult to finish once hardened.

[bigbadjon]

Ouch, I had this typed up and a customer came in before I hit submit and Lin beat me by 20 minutes.

[Scott Roush]

thanks a lot....

Lin... I'm not using oil. I'm using salt water (brine) with some surfactants (dish soap). I've read from several sources that water gives a better hamon. My only experience is that it works great for quench lines.

Bigbad.... I'm using a craftsman which is very fast and very weak... which may be the root of the whole problem...

[Scott Roush]

but... with the hamon... should I be able to see SOME indication that it's there before grinding, polishing and etching.  my quench lines have been so obvious right out of the tank.  I've clay coated twice and as soon as I start to grind I see nothing.

how much does the thickness of the clay affect the outcome.

also... Lin... I see the confusion... APG #36 is refractory cement... not oil.  Apparently it's the stuff Bob Engnath used...

[kbaknife]

Scott, quench lines and hamons are not the same thing.
IN 1084, with clay, you will get a hardening line created by the edge of the clay.
In steels like 1095/W1/2, you will get a clay induced hamon that is not a created edge, but an influenced hamon with varying degrees of visuality and hardness.
They're not the same.
I don't know how to put this into words - there is sooooooooooooooooooooooo much dependant upon steel/alloy type, austenizing source and quenchant.
The variables are almost too many to list.
For example, the top two are "hamons" whcih are INFLUENCED by the clay - not created by the clay. A hamon can only be done in a very shallow hardening steel and can be made simply by controlling the heat and putting it where necessary with no clay involved.
That's why I say "influenced". The clay influences your steel dimensions as well as heat placement.
The actual placement of the clay is NOT where you see the hamons here.
 

 

This one is 1084 and the "hardening line" is exactly where I placed the clay.

 

I would eliminate the salt water, and get some Parks #50 for 1084.
Much more reliable.

[tippit]

I take my edge down to almost finished and 400 grit belt before quenching.  I differentially quench my edge on a craddle in the oil.  My quench line is visible no matter how fine I finish or how far I grind.  Sometimes it pays to destroy a blade to see what you are getting in the steel...tippit

[Scott Roush]

Okay.... I knew that quench lines were different than hamons, but I thought that any differential hardness derived by the use of clay was a 'hamon'.  So.... you are saying that, with 1084, any pattern you get is a boundary between 'hard' and 'softer' steel right at the clay line. And a 'hamon' is a pattern that occurs by whatever means of influencing it... such as a clay coating or manipulating where the steel is taking a heat... and occurs at some distance from where the influencing factor is. do I have it?  

but, by whatever it's called... does the pattern not represent boundaries between steel of varying hardness, however it's created... whether by edge quenching, clay coating, etc?

tippit... that is what i've seen as well... the quench line from edge quenching is obvious right from the start.  just not sure if my 'hardening line' would be as obvious. i've heard of people putting on a little ferric chloride on the blade after the quench to see if there is any activity... but i haven't been able to tell much from that. perhaps i should dilute the FeCl.
btw.... got the DVD. Hope you got something out of it!

[kbaknife]

As far as your first sentence - nope.
A hamon has more to do with steel/alloy type than clay or process.
I've clayed 5160 to have a soft spine for chopping purposes, but 5160 is so deep hardening that you won't get a true hamon.
If you were to etch it, you will see a difference in the way the etchant reacts to the different hardness of the zones, but it's not a hamon.
You need a low alloy, non-chromium, high manganese steel for a hamon.
Imagine a hamon as being a STORM, where a cold front meets hot air - that disturnace you see is the ashi in the hamon.
That can also be created simply by a difference in steel thickness where the thin steel was austenized, and the thicker not, and since it is say W2, which needs to harden in milliseconds, there will be the "storm" where the hardened steel meets the unhardened steel.
You will never get that in 1084, which is borderline deep hardening, or say O1 or L6 or 5160, which are all deep hardening.

[Scott Roush]

wow... great description...  it's starting to make a hell of a lot of sense...

[kbaknife]

Good. The low alloy, high manganese characteristics of the shallow hardening steels have probably more to do with the display of ashi around the edge of the hamon than any other factors.

Just because you put some clay on a piece of steel, doesn't mean you'll have a hamon.
Not even close.
Even with the right alloy, you still need the steel set up in the right structure, the correct heat source and temp, a quenchant that will reduce the austnite to below about 900 degrees in the right amount of time, and all of this needs to be done in consideration of steel thickness, etc.
Otherwise all you are getting is differential hardness and it shows up by the etchant reacting differently to the varying hardness of the zones.