How do you sharpen

M

Metalsmith

Joined
Feb 7, 2015
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I've noticed that there is a fairly diverse list of how people sharpen their khukuri. From what I can see the best method may be using sharpening rods as they will fit in the curve of the recurve. That being said I am not sure what products work well or where to purchase them.

What tools are you using and where do you prefer to get them?
 
Hey there! Yep lots of different ways to skin this cat. We're fond of ceramic rods- they work by both burnishing and abrasion and leave a smooth, refined edge that lasts well in the hard impacts you see in chopping.

We're working on a product care page with lots of info on sharpening. It's a WIP right now but here's it is in its messy and unedited glory:

Often times when customers go to sharpen a khukuri they hit a brick wall. Convex edges? Recurved blade profiles? Even the size of khukuris can make it difficult for expert sharpeners to transfer their skills over.
While they can be quite tricky blades to sharpen a lot of the fundamentals from sharpening less exotic knives carry over quite well and once you get the hang of it it'll help a lot with other blades you may need to sharpen.

Benchstones, Whetstones and As these blades are true convex bevels with recurved profiles the use of specific edge angles and traditional bench stones can be problematic. Sticking to a specific edge angle will replace the previous convex edge and create a new flat one in its place. This isn't necessarily a bad thing, but you'll need to figure out the ideal angle yourself using the sharpie method.

The best method depends on what tools you have available to you. For me I like to use a kitchen steel followed by a diamond rod of 2 different grits then finish up with a quick strop on a thick stack of newspaper on the edge of a bench. In all steps except the newspaper the blade stays more or less stationary and the steel moves across the blade. DML shows a very similar technique here
You can also use sandpaper on a round surface with a bit of give in situations where there is a lot of steel to move- that won't be you in this instance though.

Sorry for my delayed reply I've been taking a bit of a break from knife work to focus on my second job in the leadup to christmas- a very busy time.
A lot of our customers have luck using a strop loaded with sharpening compound. You can make a strop easily from scrap leather and even put a little convexity to it to help with the khukuri recurve. I personally use a kitchen steel/ diamond file/ ceramic rod for my khukuris. You hold or clamp the khukuri still and then sharpen it freehand while moving the rod etc. Another popular method is to put fine sandpaper onto a phone book and use that as a rough strop. You can easily swap out grits depending on the intended outcome.

As these blades are true convex bevels with recurved profiles the use of specific edge angles and traditional bench stones can be problematic. Sticking to a specific edge angle will replace the previous convex edge and create a new flat one in its place. This isn't necessarily a bad thing, but you'll need to figure out the ideal angle yourself using the sharpie method.
If you wish to retain the convex bevel then he best method depends on what tools you have available to you. For me I like to use a kitchen steel followed by a diamond/ceramic rod then finish up with a quick strop on a thick stack of newspaper on the edge of a bench or a loaded belt depending on the job the knife will face. In all steps except the strop the blade stays more or less stationary and the steel moves across the blade. DML shows a very similar technique here
You can also use sandpaper on a round surface with a bit of give in situations where there is a lot of steel to move- that won't be you in this instance though.

Bench stones are very difficult and can also prematurely wear due to how much focus there is on the edges. Some diamond plates etc barely work due to how little edge there is to work off.
For large curved blades like this the general solution is to hold the blade still and move the sharpening tool across the edge. These tools work best if they're rods or at least rounded in some way. A similar concept to your scythe stones, but looking at much higher grits.

Some of these options are commonly available- here I've listed them from roughest to smoothest. Woodworking blades tend to benefit from as smooth and polished an edge as possible for edge stability reasons so these rougher grits should more be viewed as ways to clean up edge damage or reprofile rather than as daily touchup options.
-Serrated knife steels
-Sandpaper, backed with a mousepad, phone book or leather. This can be on a flat surface or glued to a wine bottle or similar for a rounded surface.
-Diamond abrasive coated knife steel
-Spyderco triangle stones and similar
-Ceramic knife steel
-Ceramic sharpening rod
-Chakmak
-Polished knife steel hone
-Leather strop loaded with compound
-polished glass, jade etc sharpening rod.

Some notes on these options:
-Leather/mousepad backings for strops help to easily maintain the factory convex curvature at the edge. However this curvature is not that important and I wouldn't be precious about it- if you prefer a different sharpening tool or like the concept of "more V-edge-like" geometry then go for it.

-Some of these sharpening options work through abrasion and some work through burnishing. We aren't fans of options that only work through burnishing (chakmak, polished knife hone) as they are less effective on the harder steel of our knives vs traditional khukuris. They also "move around" old, weakened steel which leads to inferior edge holding and worse edge stability in chopping. We like ceramic sharpening rods as they burnish (quick and easy) while also gently abrasively removing some older and weaker steel. Using more force will burnish more intensely so when doing your finishing strokes a lighter tough will work more through abrasion, giving a stronger apex.

- We like stropping and see improved performance and longevity from using it as a primary tool for touchups while working or as a finishing step after using another method. We feel that any stropping is generally better than not doing it so don't be afraid to strop on some newspaper (lightly abrasive), the inside of your belt (unloaded or with brasso/toothpaste) or just on your jeans (probably have some grit in the weave)

Here's a video from DML discussing some of these options and also showing techniques.

Powered/device based options are also possible if you want to be doing a lot of heavy reprofiling or want a super accurate and high quality end result.
-These knives are easily touched up with hard buffing wheels on a bench grinder loaded with a touch of polishing compound. It's quick, doesn't hurt heat treat and retains geometry. Not for rookies- these wheels can grab and throw a blade which can easily kill someone in its trajectory or destroy things in your workshop as well as the knife itself
-For altering geometry and fixing big dings the new worksharp is a great choice. Gets into recurves nicely, can do convex edges, lots of belts available.
-TSPROF or similar does well with big recurved blades and allows for super precise angles, high quality stones and even some custom bendable rod guides for convex.

We can give you some info on specific sharpening technologies through.

Our blades benefit from highly refined and polished edges for impact durability. Rods that can offer this kind of performance will struggle to bring very dull edges back to sharpness as they'll cut at a very slow rate. DML has a natural jade necklace whetstone that he uses on his khukuris- it's a very fine stone that's much more durable than manufactured ceramics both in terms of wear and impact resistance. I had the opportunity to test the edge he put on an interwar antique and it was excellent in keenness and durability. These are expensive though and as stated they are not as versatile.

The classic white ceramic rods are all very similar in terms of grit and durability we feel. These cut a little more aggressively however they do wear smoother with time. Marking one side and leaving that as the rough side for bigger touchups is a good move. Such rods can be "roughened up" with diamond abrasives if needed. they can crack when dropped on hard surfaces though.

I'm yet to encounter a diamond rod that was at a good grit level for our needs- all were pretty low and coarse. They're also generally diamond coated and can face durability issues from the diamonds pulling out of the resin. It's possible that there's full size kitchen steels in suitable grits (1000ish or more) and with superior construction methods. For our steel though this extra level of hardness isn't very relevant due to the low carbide content and gentler carbides we face vs super high abrasive wear supersteels. Ceramic I feel is a better option here.

We have our own ceramic rods these days if you're interested and we can make handles to suit a blades hardware/material as well as integrate into the sheath itself.
 
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