JHCC Posted November 28, 2015 Share Posted November 28, 2015 Well, I've decided to give blademaking a try, since the good folk at the local John Deere repair shop were good enough to give me a handful of lawnmower blades. (And yes, I know all about the problems with working with mystery steel. Worst case scenario, it'll be some good grinding practice on free steel. Who knows; I might even get a workable blade.) I've decided to make a Nessmuk knife, as described in George Washington "Nessmuk" Sears's 1884 classic "Woodcraft and Camping". The following photo shows (top to bottom) an enlarged scan of Horace Kephart's sketch of the original Nessmuk knife, a cardboard template of that profile, a scaled-up version (Sears was five feet tall; I'm a bit over six), and a modification of the scaled-up version that hews a little more closely to the blade profile of the original and fits my hand a bit better. You'll notice that the two modified versions have a little belly to the handles. I can't quite tell from the Kephart sketch, but I suspect that the original knife had a stag crown handle. This should make for a more secure grip. Not shown is the steel I plan to use; that's currently annealing in a container of lime. I'll post a picture of it later. Quote Link to comment Share on other sites More sharing options...
Frozenthunderbolt Posted November 28, 2015 Share Posted November 28, 2015 Good on you Jhcc - if nothing else you'll learn a lot from making it. For all that people knock them, I've had good successes with lawnmower blade. Heated to critical, canola oil quench, 2 cycles at 180-190 C. Can cut a sheet of A4 paper in one stroke and has reasonable edge retention. Known steel is better, but if you have it, play with it! Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted November 28, 2015 Share Posted November 28, 2015 If they are John Deere factory blades you should be able to find out what alloy they are by xontacting them directly. Brush Hog blades are a proprietary alloy with a high boron content, and thy take a special heat treatment. Do your research before you invest the time. Quote Link to comment Share on other sites More sharing options...
JHCC Posted November 28, 2015 Author Share Posted November 28, 2015 4 hours ago, BIGGUNDOCTOR said: If they are John Deere factory blades you should be able to find out what alloy they are by xontacting them directly. Brush Hog blades are a proprietary alloy with a high boron content, and thy take a special heat treatment. Do your research before you invest the time. That's very interesting. This one is definitely a lawnmower blade, but there are a couple of others that might be brush hog blades -- they're VERY thick and look like they've had some seriously hard use. Quote Link to comment Share on other sites More sharing options...
JHCC Posted November 28, 2015 Author Share Posted November 28, 2015 Here are the two halves of the lawnmower blade: unmodified on right, flattened and annealed on the left. And here's the unmodified half with one of the other, thicker blades. Quote Link to comment Share on other sites More sharing options...
JHCC Posted November 28, 2015 Author Share Posted November 28, 2015 Stamp on the back of the annealed section. Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted November 28, 2015 Share Posted November 28, 2015 Before I went any further I would contact JD to see what they will tell me, and also take a sample piece and try heat treating it to see how it reacts. That includes a destructive test to look at the grain structure. Mower blades are generally made from alloys to be tough and impact resistant, not hard and brittle. Google is your friend. http://www.greenpartstore.com/About-John-Deere-Mower-Blades_ep_50-1.html Sounds like they use are possibly using 5160. https://www.deere.com/en_US/parts/parts_by_industry/residential/blades/blades.page Quote Link to comment Share on other sites More sharing options...
JHCC Posted November 28, 2015 Author Share Posted November 28, 2015 That is some great info, BGD; many thanks! (Especially since the folks at JD were completely unhelpful when I called.) Definitely planning to do some hardness tests with the offcuts. In the mean time, I'll be reading up on 5160. Quote Link to comment Share on other sites More sharing options...
T.J.watts Posted November 29, 2015 Share Posted November 29, 2015 I like the blade shape, looking forward to the finished blade Quote Link to comment Share on other sites More sharing options...
JHCC Posted November 29, 2015 Author Share Posted November 29, 2015 First cutting session. (Got a couple of nice offcut bits for hardening tests.) Quote Link to comment Share on other sites More sharing options...
JHCC Posted November 29, 2015 Author Share Posted November 29, 2015 Second cutting/grinding session. Quote Link to comment Share on other sites More sharing options...
JHCC Posted November 29, 2015 Author Share Posted November 29, 2015 On 11/28/2015, 8:46:29, JHCC said: That's very interesting. This one is definitely a lawnmower blade, but there are a couple of others that might be brush hog blades -- they're VERY thick and look like they've had some seriously hard use. Although I now recollect that brush hog blades are single-ended. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 6, 2015 Author Share Posted December 6, 2015 One of the offcuts which I will be using for hardness testing. In the mean time, the 90° bend (one end in the pritchell hole, bent over by hand) seems to demonstrate that the annealing step worked just fine. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 7, 2015 Author Share Posted December 7, 2015 Sorry, image didn't upload. And here's that offcut, hardened: And with the end snapped off to show the grain. The piece is a hair over 1/8" thick. On 11/28/2015, 1:45:17, Frozenthunderbolt said: I've had good successes with lawnmower blade. Heated to critical, canola oil quench, 2 cycles at 180-190 C. Interestingly, the offcut did NOT harden with a canola oil quench, but it DID when quenched in water. Two cycles at 190°C/375°F tempered it to straw. Quote Link to comment Share on other sites More sharing options...
Frozenthunderbolt Posted December 7, 2015 Share Posted December 7, 2015 2 hours ago, JHCC said: Interestingly, the offcut did NOT harden with a canola oil quench, but it DID when quenched in water. Two cycles at 190°C/375°F tempered it to straw. Interesting. What volume of canola did you use and did you pre-heat it? Ambient temperature? In fairness to you I often tend to do a secondary edge quench in water after an initial oil dip (though I use oil only on leaf spring) that may have affected my results described. The next lawn blade I do I'll try going straight to water and see if it makes a difference for me :-) I concur with your temper cycles; i'm using a toaster oven (notoriously inaccurate) and 2x 180C gets me a dark straw with occasional patches darkening a little more. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 7, 2015 Author Share Posted December 7, 2015 4 hours ago, Frozenthunderbolt said: Interesting. What volume of canola did you use and did you pre-heat it? Ambient temperature? About a quart of canola (left over from frying chicken), not preheated. Ambient temperature in the garage (and thus in the slack tub for the water quench) was about 40°F, although I'd had the oil inside the house at about 70°F beforehand. That volume of oil would obviously be much too small for the knife itself but I figured it would be ok for this smaller test piece (1/8" T x 3/4" W x 6" L). After the quench, the oil and the test piece were hot to the touch, but not so hot as to burn my skin. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 7, 2015 Author Share Posted December 7, 2015 Forgot to mention: After the initial attempt at oil hardening, I could still bend the test piece by hand (thin end in the pritchel hole, pushing down with gloved hand on the other end). It was a lot stiffer than it had been after annealing, but still doable. Also, I did a little flattening and re-annealed of the blade blank before I move on to final flat-grinding and filing the bevels. (I also annealed the other half of the original lawnmower blade.) The low air temperature made getting the entire blade evenly to critical temperature rather tricky, but I eventually settled on burying it in the coals, shutting off the blower, and letting it soak for a few minutes. That seemed to work pretty well. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 9, 2015 Author Share Posted December 9, 2015 Ground to profile and (most of the) scale ground off. The profile still feels a little bulky, so I may trim that down a bit before I do the final flattening and bevel grinding. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 10, 2015 Author Share Posted December 10, 2015 Given the bulky feel of the blank, I've decided to use the other half of the lawnmower blade for the slimmer version from the initial design phase. I'll be making both versions together. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 12, 2015 Author Share Posted December 12, 2015 First side (mostly) drawfiled. Learning the importance of keeping the file clean to avoid galling and scratching. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 13, 2015 Author Share Posted December 13, 2015 Working on the first bevel. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 28, 2015 Author Share Posted December 28, 2015 Current state of the project (bottom to top; the picture loaded upside down): Knife #1 beveled and rough sanded, almost ready for heat treatment (I'm trying to eliminate any deep scratches that might act as nucleation sites for cracking). I ended up slimming down the handle substantially, as it felt much too bulky. Knife #2, rough cut. Rough blank for a sen, made from another (and much thicker) lawnmower blade. The width and thickness gave me a good starting place, as did the one existing bevel. I will be drawing out the two tangs and mounting wooden handles. Quote Link to comment Share on other sites More sharing options...
JHCC Posted December 31, 2015 Author Share Posted December 31, 2015 Rivet and lanyard holes drilled, shaping the scales. Quote Link to comment Share on other sites More sharing options...
JHCC Posted January 1, 2016 Author Share Posted January 1, 2016 And handle is carved and rough sanded. The scales are held on with wooden pins, which will be replaced with brass rivets in the final assembly. Next step: heat treatment. Quote Link to comment Share on other sites More sharing options...
JHCC Posted January 2, 2016 Author Share Posted January 2, 2016 And so ends my first foray into knifemaking, with a nasty crack right on the edge. I suspect that I thinned it down too much in the filing stage. Fortunately, I have another blank roughed out and ready to go. Onward! Quote Link to comment Share on other sites More sharing options...
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