Convex sharpening question

[StrangeDaze]

I have been looking at videos about sharpening convex edges and it seems there are 2 styles (or maybe i am misunderstanding)

One style is to sharpen the WHOLE convexed portion of the knife. So if it full convex, all of the way to the spine. Or if it is saber vex they sharpen up to the flat.

The other style is to just sharpen near the edge, which is what i have always done. Is this wrong? If sharpening the this style (only near the edge) does it drastically increase edge thickness? Would you eventually need a total reprofile? Or am i overthinking this entirely?

 

[catspa]

The convexes I do are basically just rounding over the secondary bevel, involving the leading 1/8” or so of the blade edge. This is not wrong, I assure you, if it meets your goal for the knife.

Sometimes it improves the cutting geometry. Sometimes it strengthens an overly aggressive hollow grind. Some knives just look better without a grind line. The result depends on your technique and equipment, but you can create thick or thin geometry in convex just like bevels.

A skilled slack belt user can produce a fair curve all the way from edge to spine fairly quickly in some steels. My unskilled attempts create a visibly uneven result.

Parker

 

[Wandering_About]

It should be fine to just sharpen at the edge. You'll have to sharpen a lot of the knife away before doing major changes to the geometry on a convex blade. There are a few exceptions (scandi-vex being the major one) but it should be an extremely rare situation where the whole bevel needs to be ground during sharpening.

 

[Obsessed with Edges]

Convexing all the way to the edge is likely to widen the edge angle and/or round the apex, at least a little bit.

The best cutting edges will ALWAYS be more V-shaped at the apex, to produce the crispest & narrowest apex. Any convex behind the edge is fine and likely beneficial to cutting, in most tasks.

Convexing is more beneficial BEHIND the apex, and especially at the shoulders of the secondary bevel, nearest to the cutting edge. Hard & crisp shoulders of V-bevels sometimes tend to dig in and bind up in tough material like cardboard, making cutting difficult. Convexing the shoulders of the bevels reduces drag in cutting tough materials like this. And polishing the convex behind the edge reduces drag even more.

The best & easiest way to convex is to create a nice, crisp V-edge first. Then lower the spine of the blade to something significantly lower than the edge angle and radius ('convex') the shoulders of the bevels, keeping the apex itself OFF the abrasive to protect its sharpness. For maintenance after convexing, just sharpen as you'd do with any V-edged blade, occasionally lowering the spine again to keep the radius ('convex') in the bevel shoulder behind the edge. Over time, that'll also thin out the steel behind the edge, which improves cutting even further.

 

[tinfoil hat timmy]

I usually just do the edge area.

I start with stones to get the actual cutting edge the way I want it. Then i use either a powered 1x30 belt or a mouse pad/phonebook and sandpaper to blend away the transition from the primary to secondary geometry.

either way I use a sharpie to see what my angle is doing to the steel.

 

[garry3]

I have been looking at videos about sharpening convex edges and it seems there are 2 styles (or maybe i am misunderstanding)

One style is to sharpen the WHOLE convexed portion of the knife. So if it full convex, all of the way to the spine. Or if it is saber vex they sharpen up to the flat.

The other style is to just sharpen near the edge, which is what i have always done. Is this wrong? If sharpening the this style (only near the edge) does it drastically increase edge thickness? Would you eventually need a total reprofile? Or am i overthinking this entirely?

A knife will become thicker behind the edge the more it is sharpened. Some knifes I thin pretty regular (like my kitchen knifes) and others I don't.