Forge Only (No Grind) Knife

Alden Sherrodd said:
G L Drew, if that knife is forged from flat stock, etch part of the bar next to where you took the piece for the knife. The anomalies may be from the rolling process. If that is the case, try forging from round stock. I think round stock has less of this sort of thing.
Good Luck and Have Fun!
Alden
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I like your explanation the best: It's the mill fault, not mine. Here is a shot of the bar I forged from and one of the blade after I sanded it to 220 grit and hit it quickly with the buffer. The lines in the 1/4 inch cold rolled 5160 were there from the mill and I just moved them around (I hope) I have some round 52100 that I will try next. You are right, this is great fun.
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You can grind those types of surface flaws out from the get go, or if you see any appear during the forging process, it's a good idea to stop and grind them out before you go any further.

The steel will follow "the path of least resistance", and heat placement plays a major role in it. Generally speaking, glancing blows aren't the most efficient.
 
If only I could be that stupid. Those knives are amazing with an incredible amount of character.
 
GL Drew... VERY COOL!!!


John- I really wanna see your pics but when I click on the thumbnails I think they actually get smaller! :p ;)

I really would like to see them!!!

To get the big pics you have to host your files somewhere. I use fototime which is like $23 a year. You can use the free ones like imageshak and photobucket but they usually lose/drop the pictures after awhile.

Anyway, once you have it hosted at a site like that then you can just copy the image link and paste it in here (with the little image icon that looks like a stamp with a mountain and sun on it). :)
 
Tai....

Does your "pipe" heat treat consist of a muffler pipe inserted into the forge to act as a heat "buffer"? ... or is it more complicated?


Edit to add:

I think I found it, Tai. Closed off pipe with something thrown in to eat up the oxygen... wood, coal?


Rick
 
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Rick, yes it's a thick walled mild steel pipe, closed off on the back end and suspended over coals or through a gas forge. I usually place a chunk of "hardwood" rather than charcoal in the back of the pipe prior to putting the blade in. The wood fills the muffle chamber with smoke, gas and volatiles, which shields the steel from oxygen. Besides shielding the steel from oxygen the muffle also helps, buffer and baffle the heat so that the blade soaks the heat more evenly. I wait until the pipe is a nice even heat, at just the temp., I want, prior to inserting the blade. With this system there is no need to work the blade back and forth through the heat. It just sits in there until it has had time for a good soak. It accomplishes about the same thing as a salt pot, but is much safer and simpler to make.

If you make the muffle pipe a little extra long at the back, for a longer wood "splint", or fuse, there's enough time to do 2, maybe 3, blades before it all burns up. I usually just do one blade at a time though.

When I’m running the muffle with charcoal, I blanket the top of the pipe with ceramic refractory wool (thermal blanket), but leaving enough space around the sides for air to circulate and draft through the fire.
 
Tai Goo said:
It accomplishes about the same thing as a salt pot, but is much safer and simpler to make.
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woah there, let's not go too far. It's like a salt pot in that it protects the blade from oxygen, but it's nowhere near as accurate nor I imagine as even, it's very even but not as even as a salt pot.
 
Sam, you can put a thermal couple in the muffle and hook it up to a pyrometer, etc... There's guys that do that. I like judging by eye though.

It does take some experience to get the most out of it, but I would argue that, "if you do it right", it's just as even as a salt pot.

As long as the conditions for heat treating are met,... the steel doesn't care what you use or how you do it. :)
 
Tai,
I have wanted to try the muffle for some time. I have a vertical forge, the interior with the insulation is 6 inches across and I usually pass the blade back and forth bringing it up to temp and it works really well. Like you I judge this by eye and feel and like to keep things simple like that. ( I'm a hammer and file guy also ) I have about a 3 inch opening on both sides of the vertical forge. Would the muffle be effective with parts sticking out on each side or do I need a horizontal forge to use the muffle.

Jerry Fisher
 
Jerry, it's o.k. to have parts sticking out, but I usually just have the back sticking out, for the hardwood splint. It makes the blade easier to get in and out if the front is fairly flush. The only thing is that your vertical forge is going to limit the length of blades you can do, without working them back and forth. So, you can either work them back and forth inside the muffle and get them nice and even, or build a horizontal one. It’s a different atmosphere inside the muffle, a nice slow soaking heat, which may take a little more time than straight in the forge. If you don't want to have to work the blade back and forth, the heat inside the muffle needs to be a few inches longer on both ends than the blade itself,... if there are thermal gradients sloping off on the ends.

The way I see it is, the blade is either even or it isn’t. If it isn’t, don’t take it out and quench it. Make any adjustments or modifications to your muffle system that are necessary and then go again.

One nice thing about the muffle system, is that it's very flexible and adaptable. You can do whatever you want with the idea,... or whatever is necessary to meet the criteria.

Some former students of mine really have taken it further than I have. Some didn’t have the experience to be confident judging by eye, so they experimented with different more controlled “muffle furnace” designs. Some used thermal couples, pyrometers, ceramic tubes, gas, electricity etc…

It’s amazing what you can do with a few weed burners, an ash can, a pipe and some refractory… :)

If you look and some of the modern industrial high tech muffle furnaces,… you just might think they make everything thing else look “primitive”. :) LOL
 
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Thanks to all those who replied concerning posting photos. It seems "img" files are the way to go. I will try, but remain challenged.

And thanks to Nick for the push.

Here's the blade after 24 hours in vinegar. 99% of the scale came right off. The dark grey is not scale, but the dark and even patina laid down by the brown rice vinegar. I may try it as an etch on some finished knives in the future.

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And, if you couldn't tell from the photo above, I suck at photography. But, anyway, here is a rough shot showing the blade after a bit of filing.

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Some random thoughts are as follows:

1. This looked really good coming off the anvil and out of the vinegar. But man when you are using a file instead of a variable speed, 2 horse, 2x72 grinder do you notice every little uneven spot! So this winds up not only being a lesson in filing, stoning, and papering, but also a lesson in really tight forging in the future. Not only are divots a real bear to get out, but I also only forged my bevels in over about 50% of the width of the blade, which also means a lot of filing to get the edge geometry I want.

2. Despite what I just said above, a really good double cut mill bastard file hogs off a lot of metal! My floor looks like I do have a grinder. The blade gets hot to the touch, and my wife asked if something was burning:D

3. I'm really having to play around with a lot of different clamping setups, filing angles, filing directions, etc. I tried draw filing a bit too early. I need to hog at this point, and draw file later. Although it is tempting to run to a grinder, even a little 4" angle grinder, I am learning a lot.

That said, my problems are just like when using a grinder: Keeping the edge centered, keeping it an even thickness, and keeping the height of my bevel relatively even as well.

Perhaps for this reason, I have settled on an approach, for now, that is somewhat like using a belt grinder. I have established a decent centerline and relatively uniform edge thickness. Now I am filing from the edge toward the spine. Although this is the opposite of some recommendations (the Loveless and Barney book comes to mind), it allows me not to run into my edge making it too thin in places, and also to use the existing bevel as guide to raise the bevel slowly up toward the spine without grinding into the spine (in theory :().

Finally, about all that blue ink. The line along the edge is just a visual check to make sure I am not filing my edge thinner while trying only to raise the bevel. The arrows were put in hastily when I finished today's work. After many tries at different directions, etc., the one denoted by the arrows worked the best, and I wanted to remember and resume my work tomorrow without any hiccups.

The photos above are sort of a test to see if they post right. If they do, I will try to take better ones in the future, and maybe even start a separate WIP thread.

Thanks again.
 
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awesome thread. two thoughts... who care about decarb since you have to sharpen the edge? The decarb is being removed from the actual working edge right?

I've recently forged a couple blades (from Aldo's 1084) completely to shape, soaked in sodium bisulfite overnight, and noticed those exact same longitudinal lines right in the exact same place.

Also... I have a single venturi burner coming from above and at a slight angle. It creates quite a hot spot to one side of my forge which makes it difficult for heat treating big blades (I do everything by eye and magnet). Would a muffle help me, or would the hotspot also occur inside the muffle if the muffle passes through it?
 
Mossanimal said:
awesome thread. two thoughts... who care about decarb since you have to sharpen the edge? The decarb is being removed from the actual working edge right?
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One thing I have seen, since decarb penetrates from all surfaces is that when people forge too thin at the edge before grinding/sharpening is if you have 1 mm of decarb penetration (and some people who forge at low temperature often get that much or more penetration) if you forge your edge down to 1 mm thick with a 20 degree included angle you are going to have a decarb zone 4-5 mm in from your edge, but if you leave sacrificial material to grind off, or forge hot enough that you scale metal off faster than decarb (scale is basically rust, if you forge hot enough steel will rust faster than carbon will diffuse out) personally I always grind before heat treat and create a carbon monoxide atmosphere in my electric kiln so I have never measured unground decarb penetration in my blades. If I get bored and can get permission once I am back at work maybe I'll do a raw blade section decarb measurement.

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A muffle isn't absolutely necessary to do a "no grind" knife, but can be helpful. Unless the decarb is severe, or clean through, you can remove it with a stone or file.

Also, in general about decarb, the idea is to try and keep it to a minimum so that it doesn’t become a problem. In the forging process you’ll always get a little even if the atmosphere in inside the forge is truly reducing, because once you take the blade out of the forge you are bringing it into an oxidizing atmosphere.

Scott, a muffle will help with your hot spot, but there is a limit to how much good it will do by itself. If you can try to minimize your hot spot first, it would help. One nice thing about using weed burners for heat treating with gas, is that they put out a big bushy flame, which minimizes the hot spot. It also helps if you can adjust the angle of the burner so that the flame swirls or spirals around the muffle, rather than shooting straight at it, and it will help if you can position the muffle so that there is a little extra distance between the muffle and the hot spot on the refractory. A thin walled pipe won't help much as much, so look for one with a thick wall. One of the main reasons for using a muffle is that they help even the heat out.
 
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A Blacksmith friend of mine showed me how to use water to cut down on the decarb on the blade while doing the finessing part of hammering out a blade. helped me out a great deal.
I dont go through near as many belts to get rid of decarb any more.
 
I guess we need to make a definite distinction between decarb and scale.

Both occur on the surface of the steel. "Scale" is the black iron oxide that forms on the very surface of the blade (which sloughs off to some degree during the forging process, and is not really part of the steel itself). It indicates oxygen and decarburization ("decarb") on the surface of the steel beneath it. The decarb layer needs to be removed from the edge through stock reduction one way or another.
 
Exactly... that was what I was trying to get at, Tai. I wanted to see if Rusty was talking about scale or decarb. Thanks for bringing it up.
 
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