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Kevin Colwell

hamon washing out from tempering clamped to straight stock

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Hey Guys,

I am getting near the end on the Tang Dynasty Dao. My problem is this: it was warped after the quench so I clamped it to a piece of straight stock during a second temper to help straighten.

 

The issue, I have polished up to 600 grit and can't see a hamon in the part of the blade where the stock was clamped. Has anyone else had the heat from tempering with another piece of steel clamped wash out a hamon?

 

I have re-clayed the blade, but it is almost down to sharp. So, I ground the edge back just a tad, and I am going to quench in Parks 50. I have this belief that water gives better hamons than Parks, but I can't really use water at this point. It is way to thin for that.

 

Any thoughts on the situation?

I forgot to mention that I saw a hamon on that part of the blade after the quench. So, it WAS there, but it ISN'T now.

 

thanks,

Kevin

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How hot did you temper? And how did you see the hamon after the quench. Did you polish it up and lightly etch it? Usually, after the quench, you get to see where the clay was but you won't see the hamon.

 

Niels.

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The blade is a san mai of cable and w2. I tempered at about 415F or 420F because it is a short sword.

 

You can see a hamon by taking the blade fresh from heat treatment and running it across the belt sander with a pretty new belt. You will be able to see where the hamon is going to be for a bit. Once the blade starts to oxidize it is not as visible. But, you can get a suggestion of what the polished hamon will be.

 

I polished to 600 grit and etched to check for a hamon just tonight, and there was one obvious for most of the blade but not the tip where I had it clamped. It is a section of the blade that hardened and all, but the hamon disappeared on 3-4 inches.

 

kc

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Clamping it for tempering should not affect your hamon at all. Everything gets heated up to the same temperature - clamp or not. The couple times that I clamped a differentially heat treated blade during tempering never affected the hamon I got. Are you sure there was hamon there to begin with?

 

Niels.

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Yes, I am sure there was a hamon to begin with. Don't get me wrong, self doubt has crept in. But, I SAW it there before I tempered the blade. At least that is how I remember it now (stupid psychologist in me makes me doubt all of my "memories.").

 

Its moot now, anyway. I have a different problem. Maybe you can help me with this one (or someone can???)?

 

I re-hardened the blade and quenched in Parks 50 (no water, just Parks).

 

The nose took a pretty serious downturn.

 

So, now I need to adjust the sori, or find a way to mount the blade that would look ok with a slight downward curve.

 

If I tried to heat treat it again, it will still be a matter of guessing what is the right pre-curve to get it straight. I am not sure how many times this blade can take being hardened...

 

thanks for the thoughts so far,

Kevin

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Kevin, I create hamons with W-2. I temper the blade to 475 degrees F so the blade will be serviceable. If the blade is a little warped I use my straightening jig. I clamp the blade and overcompensate the blade past center up to 1/2 inch or more. I put the jig and the blade in the oven at the drawing temperature, which is 475 degrees F. I let it heat up for 1 hour then quench it in water everything blade in jig. I remove the blade from the jig and some times the blade is perfectly straight the first time. If it is not straight I repeat the process until it is straight. I straightened a blade after using this process 20 times. I love it and it works. I talked to Howard Clark and Howard said he doesn't think quenching the blade is necessary, he thinks air cooling is all you need. I never have let it air cool since quench has worked fine for me. I hope this helps. The hamon has always remained and really is vivid.

 

Timothy

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Timothy - thanks, I ended up losing this blade trying to re-heat treat and then fix. Too many new imperfections from straightening and treating again. Not enough stock to remove to get them out and still have the stiffness and balance that I wanted.

 

I will make a jig. I have had so much luck with the clamp and temper method with pattern we lded knives and blades without hamons that I wanted to try it.

 

I guess the issue is that there is more energy transferred to the area clamped due to conduction being so much more efficient than convection (so the clamped area gets more energy from the environment by taking the energy that the big piece of stock absorbs from the air and focusing it on one small area of the target blade rather than just absorbing the amount of energy it would from air).

 

Honestly, most clayed blades you can cold straighten. The only problem comes when the tip is mostly or completely hardened and that is the area of the bend. That is what happened this time. I LOVE the fact that you can cold straighten most blades with hamons, which is yet another reason to use this type of heat treatment.

 

thanks, I will try your trick. I am sure it will work, I just need to make a simple jig.

 

Kevin

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Timothy - thanks, I ended up losing this blade trying to re-heat treat and then fix. Too many new imperfections from straightening and treating again. Not enough stock to remove to get them out and still have the stiffness and balance that I wanted.

 

I will make a jig. I have had so much luck with the clamp and temper method with pattern we lded knives and blades without hamons that I wanted to try it.

 

I guess the issue is that there is more energy transferred to the area clamped due to conduction being so much more efficient than convection (so the clamped area gets more energy from the environment by taking the energy that the big piece of stock absorbs from the air and focusing it on one small area of the target blade rather than just absorbing the amount of energy it would from air).

 

Honestly, most clayed blades you can cold straighten. The only problem comes when the tip is mostly or completely hardened and that is the area of the bend. That is what happened this time. I LOVE the fact that you can cold straighten most blades with hamons, which is yet another reason to use this type of heat treatment.

 

thanks, I will try your trick. I am sure it will work, I just need to make a simple jig.

 

Kevin

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I have a picture of the jig in Don Foggs tools. I used a 2 x 4 1/4 inch metal tube. I cut the top of the 2 inch side and made a c or u. I drilled 1/4 by 20 screw holes every 1 1/2" along both sides It is better to drill both sides at the same time that way they are lined up. I put a flat spacer facing the blade in front of the screw. This prevents dimpling the blade when appling pressure to hold the blade. This method was first used to straighten warped blades by clamping them straight then drawing the back with a torch three times. The edge was placed in a pan of water 1/4 inch to protect the blade. I wick the water up the tip by placing a rag in the water and putting against the tip. I had a blade with a hamon that was warped so I tried the method of over compensating the blade past center and placing it Each time it move a little. It took 20 times until the blade was perfectly straight.

 

I even took a twist out of a cable blade by drilling and taping 1/2 inch below where the top wholes and screws were drilled. I used the same method of over compensating and it worked.

 

I hope you are as pleased as I have been with this straightening jig.

 

Timothy

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