Machete sharpening on a kitchen knife sharpener

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Jan 22, 2019
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So.. using my kme would be a bit awkward on a machete so I decided to pass it through my 3$ kitchen knife "sharpener", and surprisingley it did a decent job.. my question is.. what angle do those sharpen at? It's the one with circular metal peaces on both sides of the blade. Any way to find out the angle?
 
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It's this type of sharpener.. what angle does it sharpen at?
 
It's going to depend on how much overlap there is between the discs. Basically the tangent of the arc at the point of intersection is what you'll be using to figure out approximately what the angle is.
 
Hi,
Measure the angle? Yeah measure the angle.

I used inkscape to measure the angle in the pictures,
its about 22.5 degrees give or take ,
which is common pull through slot gadget / cooking school chef steeling angle


You can also use permanent marker trick to measure edge angle,
thats paint the edge with a marker,
then put abrasive (ex stone) on an angle (ex 15 degree cardboard triangle)
and take a stroke with blade "perfectly" horizontal
and see where the marker is being removed
if its removed on edge shoulder angle is higher than 15
if its removed or edge apex but not on edge angle is lower than 15
if its removed on edge apex and behind apex then angle is 15


How do you make a cardboard triangle?
pencil and protractor
or
PocketProtractor

or pencil and ruler and 1/60 rule or calculator

Side a = 53.58984
Side b = 200
Side c = 207.05524

Angle ∠A = 15° = 0.2618 rad = π/12
Angle ∠B = 75° = 1.309 rad = 5/12π
Angle ∠C = 90° = 1.5708 rad = π/2




Or Get a pencil, millimeter ruler , and paper
-) pencil mark a spot on the blade where you will measure
-) use ruler to measure in mm the width of blade , the run, write it down ex (run 47mm)
then at the same spot of the blade
-) use ruler to measure in mm the spine thickness , write it down, divide by 2, write +result in a circle, ex 4mm / 2 = ( +2mm )
-) put pencil on table, lay blade flat against against pencil, while you slide blade slowly along pencil, raise the spine until the edge bites into the pencil then stop
then at the same spot of the blade
-) use ruler to measure in mm the height from pencil to spine, write down 11mm+spine2mm = rise 13mm
*if your ruler doesnt start counting millimeters from the edge, wrap paper around ruler, mark height, then unwrap paper and measure

then punch in some numbers into triangle-calculator hit the calculate button and get the actual angle

Side a = 47
Side b = 13
Side c = 48.76474

Angle ∠A = 74.539° = 74°32'20" = 1.30095 rad
Angle ∠B = 15.461° = 15°27'40" = 0.26985 rad
Angle ∠C = 90° = 1.5708 rad = π/2

Yes millimeter ruler works easier with wider blades.
Also its not hard to eyeball a fractions of a millimeter , ~10.5 , more or less, 10.7 , 10.9,
calipers/micrometer work better in that regard

Also a protractor and laserpointer could be used ...
 
Thanks.. I'll try to figure it out, I was hoping maybe someone already knew :) I wouldnt want it to be sharpened below 25 per side due to edge retention. It's a wood chopper after all, but I guess 22,5 is not that bad! My worry was that the angle is way lower so it wouldnt hold up after a chop or two..
 
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I sharpen mine to 20 degrees each side but I don't chop trees down with them. Depends what your cutting like any other tool. I think it's more about the thickness of whatever your chopping. For very thick stuff I use a chainsaw. But lots of guys cut heavy stuff with them.
 
Thanks.. I'll try to figure it out, I was hoping maybe someone already knew :) I wouldnt want it to be sharpened below 25 per side due to edge retention. It's a wood chopper after all, but I guess 22,5 is not that bad! My worry was that the angle is way lower so it wouldnt hold up after a chop or two..

All of my wood chopping tools, including axes, are sharpened at 15° per side or less and they hold up just fine, including on hardwoods and knotted conifers.
 
All of my wood chopping tools, including axes, are sharpened at 15° per side or less and they hold up just fine, including on hardwoods and knotted conifers.

Wow.. thats a thin edge! Dont know what kind of steel you rock.. but that seems too thin to me.. can roll and chip way too easy.. maybe if you put a 25 degree micro bevel on a 15 degree bevel.. but 15 for any serious chopping.. no.. thats more of a kitchen knife angle..
 
Wow.. thats a thin edge! Dont know what kind of steel you rock.. but that seems too thin to me.. can roll and chip way too easy.. maybe if you put a 25 degree micro bevel on a 15 degree bevel.. but 15 for any serious chopping.. no.. thats more of a kitchen knife angle..
No, a kitchen knife edge is more like 10-12° per side. The steel I'm using is just simple medium to high carbon steels ranging from 1055 to 1095, with most being 1070/1075. No chipping, no rolling. These aren't expensive customs, either. Just standard blue-collar work tools from major manufacturers.
 
Conventional sharpening advice is mostly pretty wrong. You'll see things like "use 20 degrees for a very thin knife and 25 for a more hard use blade. For chopping use 30 degrees."

This is almost completely BS. Most blades can be run much, much thinner and actually retain an edge LONGER because of the reduced stress on the edge due to the thinner blade geometry.

However, we are talking about a machete. Most machetes I'm aware of use really, really soft steel. I would guess high 40s to low 50s HRC. I recently sharpened a Cold Steel Kukuri machete. I used a file, an India fine stone, a Spyderco medium ceramic, and (for kicks) a leather strop loaded with white compound.

The result? Sucked. Really badly. The edge wouldn't really do anything worth a crap at every stage past the file. Why? It's soft. So, so, so soft! There's a reason people use a file to sharpen a machete. It's what it's designed for.

I went back to the file and made a respectable edge that would *just* slice catalog paper with a draw cut, along almost the entire length. It got tricky near the "fat end" of the kukuri where the edge shape changes rapidly.

I say forget the exact angle. Duplicate the existing edge angle with a file. Form a burr on both sides. Remove the burr completely. Then see how it performs. Getting really specific about the angle is (and I apologize for being blunt) total sharpening masturbation, because you aren't using a proper device, nor are you sure you've apexed the edge. Do the basics with a basic sharpening device (file) and you'll get good results.

I know you can do it! :)

Brian.
 
Conventional sharpening advice is mostly pretty wrong. You'll see things like "use 20 degrees for a very thin knife and 25 for a more hard use blade. For chopping use 30 degrees."

This is almost completely BS. Most blades can be run much, much thinner and actually retain an edge LONGER because of the reduced stress on the edge due to the thinner blade geometry.

However, we are talking about a machete. Most machetes I'm aware of use really, really soft steel. I would guess high 40s to low 50s HRC. I recently sharpened a Cold Steel Kukuri machete. I used a file, an India fine stone, a Spyderco medium ceramic, and (for kicks) a leather strop loaded with white compound.

The result? Sucked. Really badly. The edge wouldn't really do anything worth a crap at every stage past the file. Why? It's soft. So, so, so soft! There's a reason people use a file to sharpen a machete. It's what it's designed for.

I went back to the file and made a respectable edge that would *just* slice catalog paper with a draw cut, along almost the entire length. It got tricky near the "fat end" of the kukuri where the edge shape changes rapidly.

I say forget the exact angle. Duplicate the existing edge angle with a file. Form a burr on both sides. Remove the burr completely. Then see how it performs. Getting really specific about the angle is (and I apologize for being blunt) total sharpening masturbation, because you aren't using a proper device, nor are you sure you've apexed the edge. Do the basics with a basic sharpening device (file) and you'll get good results.

I know you can do it! :)

Brian.

Stated angles are target angles. No one is saying "it must be exactly this angle, and not more nor less". I know the angles on my machetes because I've measured them out of curiosity in the past with a digital protractor (which takes scarcely any time at all) and I grind machetes pretty much every day as part of my business, so I have deeply ingrained muscle memory for holding that angle. One shouldn't anticipate that the actual angle you end up with is inherently going to be equal to the nominal target angle, but it gives you an idea of the mark you're trying to hit. Duplicating the existing angle on machetes is usually a bad idea because the factory "edge" is almost always nothing more than a "courtesy grind" to help hog off some of the material and give the end user a head start on sharpening it themselves. So stated angles are important. It's just that they're a target you're shooting for. As long as you get in the same ballpark it's good enough from a practical standpoint.
 
My machete experience is limited. I know a little but that's all. What range of angles do you think is appropriate for a machete? I would think 25 dps would be a good starting point depending on how hard or soft the steel was. Even 20 dps, on the Cold Steel I sharpened, seems like it might roll kind of easily, especially given that machetes frequently get stuck in material and are twisted out, putting a big side load on the blade. But as I said, I don't know much. I'm interested in knowing more.

Thanks,

Brian.
 
I'd only do 20° per side if I absolutely had to, and then it'd be as a microbevel with the region behind it thinned out. I find 15° per side to be the best all-around balance. The only thing I've ever had roll a 15° per side edge was half-dry black locust branches and those are like cutting iron. A microbevel was enough to toughen the edge up and get through the job without further damage, and then I thinned it back to 15° per side again when I was done.
 
I'm surprised that 15 dps works well with relatively soft machete steel. Good to know. Do you notice a difference in different brands of machetes in terms of steel hardness and edge holding? I was rather disappointed with the Cold Steel I worked with. It might have been my technique. Might have been the steel.

I'm told that Tramontina machetes are really nice. I ought to buy one at some point.

Brian.
 
I'm surprised that 15 dps works well with relatively soft machete steel. Good to know. Do you notice a difference in different brands of machetes in terms of steel hardness and edge holding? I was rather disappointed with the Cold Steel I worked with. It might have been my technique. Might have been the steel.

I'm told that Tramontina machetes are really nice. I ought to buy one at some point.

Brian.

Cold Steel's machetes are at the very bottom of the hardness range I consider acceptable. They tend to benefit from a microbevel or small secondary bevel. But Tramontina, Imacasa, Gavilan, Hansa, and so on all have steel in the correct hardness range and are able to support such an edge pretty easily.
 
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