Best freehand guidance on sharpening knives with deep belly or curves

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maximus83

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Nov 7, 2011
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I've noticed something with a ton of freehand sharpening videos: it seems most show either sharpening big, mostly straight kitchen knives, or mostly straight folders with blades < 4". It takes a somewhat different technique to sharpen a knife that has a deep belly or large curved area. I'm interested to see how some of the 'pros' here (or anywhere) handle this challenge. Not finding a ton of great videos for doing this freehand. A couple years ago I sharpened this guy which has a deep belly curve, and to do that I used sort of a wide u-shaped motion on the stone, back and forth, to get consistent coverage of the belly area.

What's the best video you've seen on freehand sharpening a big knife with a deep belly curve? (And if you a video of your own, don't be modest, link away! :D)

Best posted advice I've gotten to date came from HeavyHanded HeavyHanded in the thread I linked on the Elmax blade:

Limit how much you scrub through the belly area. It is OK for stock removal, but once you get close, switch to a sweep at least through the belly. It is otherwise not possible to get a clean cosmetic surface on broad bevel + pronounced belly. It can be a sweep back and forth, but it should encompass the start of the belly through to the tip or just shy of the tip. Stop often to inspect and make sure the ares to either side of the sweep zone are blending in well.
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I don't use a sweeping stroke on a belly Skinners. I raise up the spine & use a back and forth motion. Check often for a burr forming then blend it in with a sweep. And remove the burr. This style blade is different. Requiring a different technique. Just my thoughts. DM
 
Well your thoughts are appreciated sir! Was hoping you'd weigh in. :thumbsup:

Is your back and forth motion kind of a wide u-shape? And do you work the belly area separately until you get to the point of blending the entire edge?
 
On your 1st question= No. Just short 1/2" back and forth, push / pull.
On a skinner the rest of the blade is normally straight. So, I work it like any other knife. Do that first and clean it up. The belly I tediously work it to the point on one side. Flip it over & do the same, removing the burr. Then lightly blend it in on each side with a sweep stroke. Check for burrs and remove then again. DM
 
This Trapper pattern made by Camillus, features 2 blades. A skinner & a drop point.
The skinner blade being thicker metal it's entire length. Thus, calling for a change in angle. DM
20201220_142715.jpg
 
^Nice, was hoping there was a Jason B. on handling belly curves, couldn't find one. Watching his vids is *really* helpful for me as I'm a lefty too, so watching him, don't have to reverse everything in my head. :D

Interesting in 2nd vid, I see a lot of stone wobble as he's scrubbing the blade--you'd think that would lead to inconsistency in the edge. ??
 
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I still do these the same way - scrub through the belly for stock removal and then switch to a sweep. The angle mechanics are exactly the same for either, I use the sweep to hide/remove inconsistent edge grind hatching. I try to hit a 45 degree grind path minimum even at the tip

The advantage to scrubbing is you can bounce off the shoulder to recalibrate - you cannot do that with a sweep as effectively.

If you really want to dial this in, pick up a cheap, short bladed Panga pattern machete and play around sharpening it, esp changing the grind path etc. After working on that a few times a regular knife with belly won't be a problem.
 
Couldn't find a cheap panga handy, but found a Tramontina bolo, and an Ontario Old Hickory 7" in 1095. I can use both of those anyway, surprised that old Hickory is like $12.

While scrubbing on the deep curve, do you not even bother to try to get super precise angle, just get in the ballpark for what you're intending, and then use the sweeps to finish it more precisely? In the past when I tried this, the scrubbing was where it fell apart, introduced so many uneven spots into the belly it was hard to fix all that afterward.

Tramontina-14-inch-bolo-machete-with-wood-handle-26624014.jpg

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I never sharpen in my wife's kitchen and I always keep the spine pointing toward me. I keep my fingers on the edge and my thumb on the spine. And I switch hands. So, ambidextrous. I realize that maybe challenging for some. DM
 
Just lock the angle by locking your wrist from pronation/supination.

Follow the curve by raising the handle by raising your elbow.

My belt Trapper model has a big belly.

CPM 15v with 23% Vanadium monocarbide volume, custom heat treatment to 67rc.

Started with no edge.
pWoHSqq.jpg


Follow the curve baby
 
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Just imagine a flat plane emerging from the centerline of the blade when held at the desired angle, like a table surface. You're trying to keep the blade presented at that same angle, and the way you do that is always going to be relative to the tangent to the curve or else you're actually producing a different angle than you intend. When riding the curve, just visualize the plane of the blade at the point of contact, and what the angle of the knife is relative to that. It should be essentially like you sliding the handle of the knife along that imaginary table surface, if that makes sense conceptually.
 
maximus83 said:
Couldn't find a cheap panga handy, but found a Tramontina bolo, and an Ontario Old Hickory 7" in 1095. I can use both of those anyway, surprised that old Hickory is like $12.

While scrubbing on the deep curve, do you not even bother to try to get super precise angle, just get in the ballpark for what you're intending, and then use the sweeps to finish it more precisely? In the past when I tried this, the scrubbing was where it fell apart, introduced so many uneven spots into the belly it was hard to fix all that afterward.

Tramontina-14-inch-bolo-machete-with-wood-handle-26624014.jpg

eyJidWNrZXQiOiAiZmlsZXMua25pZmVjZW50ZXIuY29tIiwia2V5IjogImtuaWZlY2VudGVyL29udGFyaW8vaW1hZ2VzL09OVzUwNjBhLmpwZyIsImVkaXRzIjogeyJyZXNpemUiOiB7IndpZHRoIjogNTQ1LCJoZWlnaHQiOiA0MTUsImZpdCI6ICJjb250YWluIiwiYmFja2dyb3VuZCI6IHsiciI6IDI1NSwiZyI6IDI1NSwiYiI6IDI1NSwiYWxwaGEiOiAxfX19fQ==
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When I'm doing a scrub on the belly I'll use an overlapping zig zag pattern. For me, this is where I try to be as precise as possible. Use more scrub on a shorter pass.

I cannot feel the shoulder as well when using a sweep a la Murry Carter, so if the scrub wasn't flat, it isn't going to improve much with a sweep.

Traditionally this is where my edges would have the most angle deviation - going back and forth from a guide to freehand this is where it would take more time on the guide to correct. In the last two years or so have improved on this quite a bit, and the key was to go back to basics and apply the overlapping scrub zig-zag.
 
Yes ^. I find on wider blade styles you can sweep more on the belly in working it's edge, than on a more narrow blade. Still, watch and don't let the bevel increase in width. DM
 
I just follow the edge with oval or round diamond, ceramic, and glass rods.
 
David Martin said:
I never sharpen in my wife's kitchen and I always keep the spine pointing toward me. I keep my fingers on the edge and my thumb on the spine. And I switch hands. So, ambidextrous. I realize that maybe challenging for some. DM
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Hey David.
Do you always sharpen with the spine towards you?
 
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