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Straightening - breaking...


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Looks like you're getting some great tips here and moving forward quite well. Excellent! Please don't forget to keep sharing what you try and how it turns out.

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A couple of things you could try.

Mix a little charcoal powder with your refractory coating. It acts as a binding agent.

The temper line is going to be about an 1/8" to 1/4" lower than your refractory coating so think about where you want your line and make it a little higher.

Once your refractory dries you can sand it dowm to the thickness you want. Also if one side is thicker than the other youcan get warping because the thinner side is going to harden A little more. This will pull to that side

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If you use the Rutland Furnace cement, do not let it dry before heating to critical for the hardening. Put that sucker in the forge or oven while the stuff is still wet.

 

If you are hardening in a propane forge, I would suggest getting a square tube (3" x 3"x 1/8") to heat the blade in while the tube is in the forge.This keeps the heating of the blade more uniform and you can see the coloration of the blade much easier. Just drill a couple of holes in one wall and insert some round rods through the holes to keep the blade standing on the spine with the edge up in the tube.

 

Tube inserted into forge
Heat tube (2).JPG

 

Shown so you can see the rods in place

Heat tube.JPG

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Update:

 

Alright - it survived the quench, clay didn't fall off, and there was absolutely no warpage to the blade!

The refractory cement came off easily as I undid the wire too - which is ok I guess. ^_^

quench survival.jpg

 

It is currently in my kitchen oven at +200C - and will sit there for a total of two hours. I'll then bring it with me to work to do the last bit of grinding before I start polishing.

 

I worry about the hardness though... I tested it with files, and the 55HRC file felt as if it bit the steel a littlebit as I applied a bit of force to it. Perhaps I have heated and re-heated the steel too many times - resulting in a loss of hardness. Keep in mind, the 126 layers of twisted steel took me about 18 hours of work alone. That is alot of re-heats. The steel supposedly hardens to 63HRC, so if I could only get it up to about, say 53HRC - that is a substancial loss.

 

I will re-check the hardness once I've sanded it down a bit... But I fear that the blade is indeed too soft. :unsure:

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1. If you use the Rutland Furnace cement, do not let it dry before heating to critical for the hardening...

 

2. If you are hardening in a propane forge, I would suggest getting a square tube (3" x 3"x 1/8") to heat the blade in while the tube is in the forge...

1. Yeah, that is what I gathered as well from reading some forum posts out there. ^_^

2. That is an excellent idea Josh! - thank you very much. I'll look into getting one of those. :)

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You are probably experiencing a thin layer of surface decarburization with the files. That should go away after you remove a couple of microns thickness.

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I might have been a bit hasty when I said "it survived the quench"...

 

Take a look at these:

left 01.jpg

left 02.jpg

 

Other side:

right 01.jpg

right 02.jpg

 

Some closeups of the longest cracks. (x50):

 

Spine:

KNIV01.jpg

 

Spine Side:

KNIV02.jpg

KNIV03.jpg

 

Micro fractures appear everywhere the blade has been in more or less direct contact with the oil, spanning inwards towards the middle.

 

the blade is of a 3 bar san-mai construction with two 126 layer twisted bars on the edge and spine side, with a 12 layer non-twisted bar running inbetween them in the middle. And then there is also the edge steel that runs through the entire knife.

 

The blade was differentially hardened using refractory clay as seen on earlier image.

 

the blade was brought up just past non-magnetic and quenched in pre-heated food oil (+50 - 55C)

 

All measurements are in metric. (mm)

Edited by Alveprins
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Ouch! :(

 

I would bet those were caused during the first quench that was too hot and caused the warping. it hurts to lose that much work, regardless.

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Ouch! :(

 

I would bet those were caused during the first quench that was too hot and caused the warping. it hurts to lose that much work, regardless.

 

Well, I DID lose the billet in the water bucket TWICE, and I did quench the blade twice also...

 

I wonder though... Should I still finish this knife, or just throw it away?

I dont think it will break or anything during normal use... It IS a kitchen knife...

 

EDIT: I have another knife made from the same billet. I only have the filework on the spine of it left before I will quench that one as well. It will be interesting to see if the same thing happens to it - since it has not been pre-quenched like this one.

 

EDIT 2: I've been trying to bend and break the blade using my hands and slamming it against a wooden table for a while now - to no avail... I think the blade will be usable - cracks aside. Unless rust gets in there, and weakens it over time that is...

Edited by Alveprins
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If you use the Rutland Furnace cement, do not let it dry before heating to critical for the hardening. Put that sucker in the forge or oven while the stuff is still wet.

 

If you are hardening in a propane forge, I would suggest getting a square tube (3" x 3"x 1/8") to heat the blade in while the tube is in the forge.This keeps the heating of the blade more uniform and you can see the coloration of the blade much easier. Just drill a couple of holes in one wall and insert some round rods through the holes to keep the blade standing on the spine with the edge up in the tube.

 

Tube inserted into forge

attachicon.gifHeat tube (2).JPG

 

Shown so you can see the rods in place

attachicon.gifHeat tube.JPG

When I leave it wet it just puffs up and comes off in places. Then I get hard spots where I don't want them. I let it dry for a couple of days then gently preheat before I put it in the oven.

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Yikes that hurts to look at. Agreed with Alan, those probably started when it was quenched too hot the first time...which also caused your break in the first place, judging by the grain. Beautiful shape and filework though. :)

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Yikes that hurts to look at. Agreed with Alan, those probably started when it was quenched too hot the first time...which also caused your break in the first place, judging by the grain. Beautiful shape and filework though. :)

Thanks...

 

Anyhow, after trying to break the knife, and failed - I've concluded that I will finish it despite the micro fractures.. Heck - it might even bring characteristics to the overall look of the knife. It will be an interesting moment when I quench the sister-knife to this one though - to see whether or not it cracks up as well. I just need to do the filework on it first.

 

PS: A friend of mine suggested doing the filework AFTER hardening - so I didnt waste my time on a cracked blade......... :lol:

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You could always reweld another jacket over it and reharden/temper. You might get those cracks to weld back or at least weld a solid layer over them.

 

Filing a hard blade is a bear and it usually costs you a file or two..........

Edited by Joshua States
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Joshua means that you could use your blade as the center piece for san mai. Put a piece of good steel on each side and weld it together. Or at least I assume that is what he means. B)

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Joshua means that you could use your blade as the center piece for san mai. Put a piece of good steel on each side and weld it together. Or at least I assume that is what he means. B)

That would cover up the 3-bar damascus blade entirely.. Might as well just make a new knife. :P

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Here is a quick snapshot of what it looks like. I took it up to 12000 grit on my Naniwa stones and etched it for a few minutes:

knife fail.jpg

 

As you can see - the cracks are quite prominent...

Also - the pattern of the two twisted bars barely show. There is very little contrast going on there - which I really don't like. It appears almost homogenous.

 

The differential hardening is somewhat apparent, but not along the entire length of the knife. Towards the tip - it disapears entirely.

 

I really don't know what to do with this knife. About 48 hours of work now. Not sure if I should put any more into it. I dont think I can sell this knife. It is a pure loss both in material and time.

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I wouldnt count it as a loss.

You learned a few new tricks to the process with this one. Tricks your not likely to forget on the next one.

 

My first semi successful forge weld experiment ( a stack of A36 flat bar ) all forge welded together at one end hangs on the wall in my shop, to remind me that while im not good at it yet, I can infact do it.

Finish it up and keep it and use it yourself.

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I'm far from an authority, but when it comes to clay I am secsessfully using plain ol drywall mud ( gypsum) let dry a day before then into the forge!

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That does look a lot like surface cracks due to forging at too low temperature (in particular bending)...

 

Hmm, you may have a point. The cracks seemingly only appear on the bars of twisted steel.

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That would cover up the 3-bar damascus blade entirely.. Might as well just make a new knife. :P

Not entirely. If you used thinner pieces of steel for the jacket, by the time you ground the bevels in, most of the jacket would be removed, leaving the center billet showing. All that would be left of the jacket is the upper 3rd of the blade which is where the cracks are. Now the cracks are covered and sealed inside a welded jacket.

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Not entirely. If you used thinner pieces of steel for the jacket, by the time you ground the bevels in, most of the jacket would be removed, leaving the center billet showing. All that would be left of the jacket is the upper 3rd of the blade which is where the cracks are. Now the cracks are covered and sealed inside a welded jacket.

Ah, I see. :)

 

Oh well, I decided to finish the knife as it is instead. I saved my more expensive handle materials for the 2nd knife I managed to squeeze out of the billet - so I will be using those for that (unless it comes out all cracked from the quench as well...). I finished this one using ebony and maple burl. ^_^

 

The finished knife and complete video walkthrough of it's creation can be found HERE.

Edited by Alveprins
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