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“Knapped” Steel Blade Tutorial - for Ford


tsterling

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I’ve finally managed to get around to making another “knapped” steel blade, and I’ve documented the process I use. First, however, when you’re trying to synthesize the features of something in your art, it’s very important to understand the appearance of that which you’re trying to imitate.

 

Along that vein, I dug up two examples of knapped stone blades, and also marked out the flake scar shapes and patterns. One example is of a pressure flaked blade, and the other is of a percussion knapped blade. Both of these stone blades are by Dr. J. P. Higgins, a friend of mine and expert knapper.

 

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The first example is of a pressure flaked blade, this one in black obsidian (volcanic glass). Pressure flaking is performed by using a hand held tool with a small point and literally pushing a flake off of the stone with hand force only. Pressure flakes tend to be much smaller than percussion flakes, and appear to be longer (actually only more narrow and more shallow). This example is an “oblique” technique, and the flake scars run across the blade at an angle. “Parallel” flakes run across the blade at 90 degrees. Knappers normally try to make flakes from one side meet up with an opposing flake on the other side.

 

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The above is an example of “percussion” knapping, this blade in a heat-treated jasper. Percussion knapping removes flakes by using a small but dense object to strike flakes from the stone. Percussion flakes are larger, wider and deeper than pressure flakes. I usually simulate percussion flakes in my steel blade work - simply because I like the looks better.

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Here’s my blade blank, along with a kozuka-like handle in copper (see Ford Hallam’s kozuka making tutorial on The Carving Path Forum - http://www.thecarvingpath.net/forum/index....&hl=kozuka). This will be a small, narrow blade so the blade blank is from 1/8 of an inch thick 1080 carbon steel. For larger blades I normally use 3/16 to 1/4 inch thick carbon steel. I previously designed the blade length and shape, and I’ve rubber-cemented a paper copy onto the steel blank for use as a reference during grinding and shaping. The blade steel has not been hardened or tempered at this point, the blade portion is 5 3/4 inches long, 8 3/4 inches overall (not including the handle).

 

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If you examine any knapped stone tool, you’ll find that it is shaped like a lens in cross section. Here I’m using an angle grinder to grind that rough shape into the blade blank. I’ve clamped the blade into a vise:

 

NOTE: THIS IS A HAZARDOUS OPERATION WITH THE BLADE STICKING OUT LIKE THIS. PLEASE USE CAUTION WHILE WORKING WITH IT, AND REMOVE IT FROM THE VISE ANY TIME YOU ARE GOING TO LEAVE IT UNATTENDED!

 

Also, with a thin blade like this, you should only grind the portion of the blade nearest to the vise - the grinder will set up vibrations in the blade if grinding too far from the vise. This can damage the blade and possibly you as well. When you need to grind farther out on the blade, reposition the blade in the vise.

 

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Cross section of the blade blank should look something like this to start with.

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Here is another option for holding the blade for hand filing. I use a standard woodworking clamp fastened in a bench vise to hold the blade horizontally.

 

Once again, this is a hazardous position, MAKE CERTAIN ALL THE CHILDREN HAVE BEEN RUN OUT OF THE SHOP - THIS IS RIGHT AT EYE LEVEL FOR LITTLE PEOPLE!

 

You’ll only want to work on the portion closest to the clamp because of vibration - this isn’t as much of a problem on larger, thicker blades, but was definitely a problem with such a long, thin blade as this.

 

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Here’s the blade in the handle, with a rough lens shaped cross-section ground and filed in.

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Here’s a closer look - note I’ve left the center of the blade at the original material thickness - we’ll be needing that thickness shortly.

 

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Here I’m marking in the centerline of the edge portion of the blade. This will provide a reference for how deep we’ll be grinding in the flake scars, so we can keep the edge reasonably straight and centered. I first darken in the edge with a Sharpie permanent felt tip marker (dark colors only). Then, I select a diamond burr size that is nearest to half the blade blank thickness (other types of grinding/sanding burrs will work as well). I lay the blade blank on a flat surface and then draw the burr along the edge. This will scrape away part of the Sharpie marker color, leaving a bright mark. Flipping the blade end-for-end I repeat this, leaving two closely spaced parallel bright lines. The center of the edge is halfway between these two marks. Repeat for the other side. This is a quick and dirty method of center marking the edge, and works surprisingly well.

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These are the tools I use for grinding in the flake scars, a Foredom flexible shaft grinder and small drum sanders with medium grit sanding sleeves. I have three sizes, ranging from 1/2 inch diameter up to one inch diameter. I keep a coffee can of water to cool down the blade as I grind. I hand hold the blade against the carving station you see the handpiece lying on. I can grind about two flake scars before the blade is too hot to hold.

 

NOTE: DUST MASK AND EYE PROTECTION ARE REQUIRED FOR THESE GRINDING OPERATIONS! YOUR EYES WILL BE VERY CLOSE TO HIGH-SPEED GRINDING, AND LOTS OF VERY FINE SILICA DUST COMES FROM THE SANDING SLEEVE!

 

I’ll be using the middle sized one (3/4 inch diameter) for this narrow blade, since it will most closely simulate a short, smallish flake scar. A single sleeve was enough to do this 6 inch long blade by reversing the sleeve halfway through the grinding. I find I use the far end of the sanding drum the most, leaving the closest end pretty much untouched, so reversing the sleeve will make it last longer. I also leave the sleeve a little long on the drum, so I won’t hit the metal end of the sanding drum on the blade during grinding. The sleeve will also bend at the end slightly, allowing detail grinds using just the end portion.

 

I’ll also use the very smallest sanding drum when I do the last inch at the tip of the blade where the smallest flake scars will be.

 

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I’ve drawn in (using the Sharpie permanent felt tip marker) the first few flake scars. I always start at the base of the blade and work towards the tip. Since the base of the blade is where the blade will meet either the handle or a blade guard, it is the most critical area in terms of fit and function. I grind in that area first while I’m fresh and alert.

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Here’s the first flake scar ground in. I’m paying special attention to the base of the blade’s edge, where the blade guard will touch. I want the edge to come to a point there without a flat spot that will look bad when the blade is installed in the handle. As I grind in the flake scar, I rock the grinder up and down and move it along some of the length of the sanding drum so the scar is actually curved along the lens shaped cross-section.

 

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Starting to grind a flake scar (start at the edge, then rock the handle upward cutting in farther towards the center).

 

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Finishing grinding a flake scar in the center of the blade. Repeat as necessary.

 

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Here’s the second flake scar ground in (on the far side of the blade). I’ve marked in the edges of the scars with red to show how they overlap in the center of the blade.

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Here’s the third flake scar. You can really see the lens-shaped curvature in the third scar in the enlargement. Also note I’ve left the intersecting edges of the scars high. Don’t forget to turn the blade over and do the same for the other side. I try to keep both sides of the blade fairly even as I work the flake scars. There’s a lot of adjusting as I go along, keeping the sharp edge fairly centered. I want a little undulation in the edge for visual interest, but not too much!

 

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Here’s something to avoid as you work along. As I’ve worked both sides of the blade, I’ve left little flat spots along the edge of the blade (see the red arrows at the top and bottom enlargements). I want the flake scars on both sides of the blade to meet in the center forming the sharp edge, but without these flat spots. I’ll correct this by grinding both meeting scars a little more at the edges, forming a small dip in the edge when viewed from the top or bottom of the blade.

 

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Here’s a view of the same points from above in the finished blade - note how the edge curves in between two sharp points. By a little more grinding, I created the curve and eliminated the flat spots so the higher boundaries between two adjacent flake scars meet as points at the edge.

 

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Here you can see where I removed the flat spots with the extra grinding. However, I don’t want two adjacent flake scars on one face to meet perfectly with two others from the other face of the blade. Notice How I’ve offset them slightly. Too much perfection doesn’t look right in a blade of this style.

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Here I’ve completed 5 rows of flakes, on both faces of the blade. Notice how the flake scars from one side of the blade “generally” meet up with a matching flake from the other side, but I’ve introduced enough offsets to make the scar pattern more random and interesting.

 

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At long last, here’s the blade with all the flake scars rough-ground in. I’ve done a little quality control and checked to make sure there are no flat spots left along the sharp edge, in between adjacent flake scars, or in the center. Now is the time to fix any problems.

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There are still some grinding marks left in the flake scars at this point left by the sanding grit. I’ll go back and use a Cratex grinding wheel (this one is fine grit, I think - it’s brown, whatever that means) to remove most of those sanding marks. Now be careful here - you’ve worked hard to keep the edges crisp looking, don’t polish them off now. I’m not looking for a bright and shiny finish here, just something to remove all those little parallel sanding marks. This is supposed to have a little bit of a rustic look to it, so don’t go too crazy making it all perfect.

 

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Here is the finished blade after heat treating and before descaling, slight polishing and bluing. Since this is such a long and thin blade, I tempered it at 450 degrees F (232 C) so it isn’t quite as hard (and therefore brittle) as my normal blades (I usually temper simple carbon steel at 425 degrees F - 218 C). I’m not going to go into the ins and outs of heat treating. Lots to say about that subject, and there are more in depth discussions available on www.thecarvingpath.net or http://forums.dfoggknives.com.

 

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Here’s the finsihed blade after a slight polishing with buffing compound, followed by a little gun blue (Birchwood Casey Super Blue). I’ve added the kozuka-like handle (copper) and a fossil ivory guard and butt cap, just because I thought it needed something. Now all that is left is to add some carved embellishment to the handle and then patinate the copper.

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Here are a few other examples of “knapped” style steel blades, just for reference. The only differences have been the sizes of sanding drums used, and the thickness and width of the original carbon steel bar stock.

 

Hope this tutorial has been enjoyable and of use to you.

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Guest ford hallam

Cheers Tom,

 

very clearly demonstrated. I reckon I may well give one a go myself, sometime.

 

Of course you realise you've done it now......

Now everyone is going to be making blades like you ;) , they'll flood the market with cheap copies ;) .

 

thanks again, Ford

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Thanks, guys, hope this is of use to you.

 

Of course you realise you've done it now......

Now everyone is going to be making blades like you ;) , they'll flood the market with cheap copies :( .

 

thanks again, Ford

 

Ford, so true, but this is always the risk when knowledge is let out. However, seeing others make good use of that knowledge is also the reward... Like most things in life, there are two edges to this sword! ;)

 

Cry Cheers! and let slip the dogs of knowledge!

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My question to you and any others out there is....will 440C stainless blue up?

 

Mike, 440c and other stainless steels don't blue, at least not with the normal cold and hot gun blues. Brownells does make a bluing for stainless gun parts, but aside from the set up being different from their normal salts it doesn't give reliable and consistent results. You can heat blue 440c some extent, but it's probably going to be way over your tempering temperature range. When Bill Cheatham did his knapped-looking blades years ago in stainless steel he'd give them a bead blasted finish. This and your paint are probably your best bets for stainless.

 

David

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Thank you, David. I'll go with the paint method , since bead blasting looks like what it is. I always appreciate your input, since you know that I have total respect for your metal working abilities.

 

Tom,

I have a neat book entitled: Clovis Settlement Patterns by Joseph M. McAvoy. It's subtitled: "The 30 Year Study Of A Late Ice Age Culture On the Southern Interior Coastal Plain of Virginia" It was published in 1992 by the Archeological Society of VA.

In it are plenty of decent photos, but particularly interesting are the many line drawings of flaked artifacts. Picture size limitations here might not be condusive to study, but I could make you copies and email them to you if you are interested in checking out the flake patterns. Here's an example...

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Thanks, Mike. Another thing I thought of is French greying. After "knapping" the blade and giving it a reasonably good finish, place it in ferrich chloride until it is greyed. Might look better than bead blasting. I guess if you wanted to get artsy you could hit the high spots with steel wool, very fine sandpaper or your buffer to highlight it. You could also completely finish the blade before heat treating it, then leave the blade alone with it's greys and blues.

 

Tom, thanks for posting your tutorial. Your "faux knapped" blades look great! It's inspired me to try texture on steroids.

 

David

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Thanks, Mike. Another thing I thought of is French greying. After "knapping" the blade and giving it a reasonably good finish, place it in ferrich chloride until it is greyed. Might look better than bead blasting. I guess if you wanted to get artsy you could hit the high spots with steel wool, very fine sandpaper or your buffer to highlight it. You could also completely finish the blade before heat treating it, then leave the blade alone with it's greys and blues.

 

Tom, thanks for posting your tutorial. Your "faux knapped" blades look great! It's inspired me to try texture on steroids.

 

David

Thanks, David.

I actually have a bottle of that. It's Radio Shack Etchant Solution. I'll give it a try. Hmmmm. I wonder what it'll do to copper, since I believe it leaches the copper out of the mat'l when etching. I'll keep you posted.

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Thanks, David.

I actually have a bottle of that. It's Radio Shack Etchant Solution. I'll give it a try. Hmmmm. I wonder what it'll do to copper, since I believe it leaches the copper out of the mat'l when etching. I'll keep you posted.

 

Mike, I use the etchant from Radio Shack to etch my damascus. You do not want to use the same batch of etchant on copper. If you do, the next time you etch steel you will have a really ugly layer of copper on your blade. When I etch mokume with copper in it I use an old bottle of the etchant that won't really do much to steel anymore.

 

David

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  • 3 months later...

Tom,

 

i know you said you don't want to go into heat treatment here, but it strikes me that there are a couple of heat treating problems particular to this kind of blade. Firstly, with such an uneven 'grind' , how do you stop the blade from warping, or even cracking? Second, it seems that you are grinding down pretty much to the edge(s) before hardning - do you find de-carb to be a problem?

 

thanks,

jake.

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Firstly, with such an uneven 'grind' , how do you stop the blade from warping, or even cracking?

Second, it seems that you are grinding down pretty much to the edge(s) before hardning - do you find de-carb to be a problem?

thanks,

jake.

 

Hi Jake,

 

Excellent questions. First, as far as warping goes, I know it looks like an uneven grind, but in actuality it ends up pretty symmetrical. The dips occur in pretty much the same places on all four surfaces of the blade, plus or minus a little. Then, of course, the "ribs" do the same, and probably act as stiffening components. So (as far as I know, which doesn't necessarily mean much...) there isn't really any unevenness to cause warping. At least that's my story and I'm sticking to it. I've never had one of these warp - knock on wood. As far as cracking, I use a vegetable oil quench, so I don't think cracking is much of an issue (or maybe I've just been lucky - my old boss always said it was better to be lucky than good). I've played a little with a water quench, and had absolutely dismal results. I think I'll leave the hamons to you!

 

Decarb doesn't seem to be a problem with these, either. Firstly, they end up being more like a serrated steak knife than a traditional cutting edge. If they were to actually be used, the user would have different expectations than from a traditional edge. Secondly, since they are either only partly forged, or just stock removal for a thin one like this example (leaving a fairly thick edge) the clean edge steel (after grinding) is only exposed to heat once, and that only to critical temp just before the quench.

 

For a traditional cutting edge I like to grind or file pretty close to the final thickness, and then rely on a wet wheel to remove any decarb during final sharpening. I think I have more luck this way - a final grind and losing the temper by getting it too hot is just too easy for me to do if I leave the edge thick. A poor temper is just as bad as a decarb situation. As most of my blades have this sort of "primitive" look to them, I haven't needed a really fine finish on them (yet!)...

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