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So I have been making knives for over 4 years now but recently (as in the past 3 or 4 months) I have been having an issue with my steel warping. Oddly, it's warping inside the forge, not in the quench. I am not doing or using anything different now compared to before. I will put the blade into the forge to normalize and every time, it warps right in front of my eyes. I pull it out, hammer straight, and put it back in. Only for it to warp again. I have never had this issue before. Anyone know what is going on?

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So many questions to ask before suggestions can begin.

What type of steel?

How thick?

What kind of blade grind?

What temperatures are you working at?

What type of forge are you using?

Are you normalizing as part of the final heat treat or in the course of forging?

Is the warping only occuring during a normalization cycle?

Others will probably have different questions from their perspective(s)

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Concentrated heat was my first guess as well. Or uneven grinds, perhaps? Really need answers to Verns questions or this is all just speculation. 

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To throw out SWAGs for the record,

Fullering the blades?

If a gas forge erosion or unnoticed shifting in the burner position causing hot spot? Or hot spot combined with winter weather temp of ambient air. (Didn't look up your location)

Not popular but.... laying hot blade on cold anvil ? 

Just to make sure we're on the same page, are you normalizing by taking it to recalescence and then it's warping ?

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1 hour ago, Vern Wimmer said:

So many questions to ask before suggestions can begin.

What type of steel?

How thick?

What kind of blade grind?

What temperatures are you working at?

What type of forge are you using?

Are you normalizing as part of the final heat treat or in the course of forging?

Is the warping only occuring during a normalization cycle?

Others will probably have different questions from their perspective(s)

-Usually 1095 or Damascus (1095 and 15n20) happens with both. 

-Usually about 7/64 thick, give or take.

-full flat grind (kitchen knives)

-single burner gas forge coming in from side angles back ( circular forge)

-Normalizing for final heat treat

-Warping occurs during norminlizing while heating up as well as cooling down outside of the forge

I can watch the blade curve like a potato chip while inside the forge. This has only started happening the past couple months. I haven't changed anything I use or do. I just don't get it. 

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Actually, with blades that thin, and usually wide for thickness I am surprised that you haven't had warping problems before. I don't generally deal with kitchen knives because of that. I found myself leaving them thick and doing a lot of grinding to dance around the problem. Hence I was spending more time than I wanted to on them. Usually for me it was in the quench.

Since you have a history without the warping it seems that something, you haven't noticed, has changed. Again you are obviously unaware of what it is. (Yes, Captain Obvious hijacked my phone).

If your materials, design and method of work haven't changed that leaves the equipment. 

I go back to Alan's suggestion of a hot spot that has developed through wear, perhaps in the burner or to the lining of the forge that has gone unnoticed. Thin blades are prone to accentuating such a thng IME. I'm asing this on the fact that, what happens, in detail, to the heat in the forge is the thing you have the least control over and is also the hardest to observe. If all other things have not changed that is the only thing left that could change.

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I'd say it's the best bet. If you don't use an anti-scale a pipe baffle with one end closed and a piece of dry wood or charcoal in it would cut down on decarb as a bonus.

I would assume, if you do use an anti-scale you have ruled out a change in that as the culprit.

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15 minutes ago, H Seidel said:

What do you think about trying a tube down the center of the forge to heat the knife in

I think that's the logical place to start. It really sounds to me that uneven heating, and as a byproduct uneven cooling, is the most likely cause of your warping issues. A pipe in the forge would even out the heat.

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