Razor sharp scandi edge?

[kakefat]

So I´ve been getting some free hand sharpening done and finally getting some good results. I can polish most of my edges so they shave hair effortlessly now which is a lot of fun. However I tried sharpening a mora knife with a scandi edge today and while it was very easy to do, as is intended, and it got sharp, it wouldn't shave hair off my arm. I know its not exactly designed for shaving so its not too surprising but I find it a bit strange that it wouldn't shave at all.

So is it my skill that is still lacking or are scandi edges just not going to shave?

 

[Obsessed with Edges]

What did you use to sharpen it?

It may not be fully apexed, or there's a residual burr left behind; these are the two things almost always getting in the way of shaving sharpness. The edge angles on these are narrow enough that shaving shouldn't be a problem, assuming it's sharpened with the existing Scandi bevel laid flush to the stones.

BTW, I just picked up a Helle 'Dokka' folding Scandi (with a laminated stainless blade), and I'm noticing it may be experiencing some burring issues. I haven't done a proper sharpening on it yet, though; just lightly touching up the existing factory edge (which seems to show a very narrow, subtle secondary bevel). Like yours, it's pretty sharp, but shaving isn't where I want it to be. Still need to get acquainted with the steel, as I don't yet know what it's capable of.


David

 

[kakefat]

I used some Norton combination water stones. They usually work very well on high carbon steel. I started at the coursest side which I think is 220 and held the knife steady so the angle should be the same all over. I laid the bevel flush against the stone like you mentioned. Then moved to 1000, 4000 and 8000. It should be perfectly apexed and the edge should be clean.

Just had a look at that folder. Seems like a very functional design.

 

[Obsessed with Edges]

I used some Norton combination water stones. They usually work very well on high carbon steel. I started at the coursest side which I think is 220 and held the knife steady so the angle should be the same all over. I laid the bevel flush against the stone like you mentioned. Then moved to 1000, 4000 and 8000. It should be perfectly apexed and the edge should be clean.

Just had a look at that folder. Seems like a very functional design.

The only things that would prevent an edge from shaving are a too-wide edge angle (shouldn't be an issue here), folded burrs, or a rounded or incomplete apex. I'd first assume the apex isn't as crisp as it needs to be, and go from there. Have you tried stropping the edge yet?

The grind angle on my Helle seems to be about 17°-19° inclusive. If the steel is a bit soft for such thin geometry, it's also possible a true shaving edge might fold over very easily, which could mimic a burr. At this thin geometry, it could still leave a decent working edge for tasks appropriate to these knives (bushcraft, etc); but I don't yet know if maintaining (durable) shaving sharpness is realistic in these.


David

 

[kakefat]

The only things that would prevent an edge from shaving are a too-wide edge angle (shouldn't be an issue here), folded burrs, or a rounded or incomplete apex. I'd first assume the apex isn't as crisp as it needs to be, and go from there. Have you tried stropping the edge yet?

The grind angle on my Helle seems to be about 17°-19° inclusive. If the steel is a bit soft for such thin geometry, it's also possible a true shaving edge might fold over very easily, which could mimic a burr. At this thin geometry, it could still leave a decent working edge for tasks appropriate to these knives (bushcraft, etc); but I don't yet know if maintaining shaving sharpness is realistic in these.


David

Hm.. I suppose its back to the stones with it then. I haven´t stropped it yet but I generally want my edges to be good before stropping as I feel its cheating to use a strop to correct my mistakes

 

[Obsessed with Edges]

Hm.. I suppose its back to the stones with it then. I haven´t stropped it yet but I generally want my edges to be good before stropping as I feel its cheating to use a strop to correct my mistakes

Ideally, we'd all get shaving edges straight from the stones )). Using a strop is a good way to test just how close we are, coming off the stones. If it still won't shave after stropping, it's an indication the edge is still a bit short of fully-apexed. Additional stropping won't usually fix that by itself, unless the edge is very close to a full apex, and if the compound used is capable of removing the additional metal necessary to get it there, and the substrate firm enough to prevent the rounding that would otherwise happen with aggressive compound on softer backing.


David

 

[kakefat]

Ideally, we'd all get shaving edges straight from the stones )). Using a strop is a good way to test just how close we are, coming off the stones. If it still won't shave after stropping, it's an indication the edge is still a bit short of fully-apexed. Additional stropping won't usually fix that by itself, unless the edge is very close to a full apex, and if the compound used is capable of removing the additional metal necessary to get it there, and the substrate firm enough to prevent the rounding that would otherwise happen with aggressive compound on softer backing.


David

Ok. I´ll take all that into consideration and try again. Thanks

 

[awestib]

Ok. I´ll take all that into consideration and try again. Thanks

It could also be a burr as mentioned above already. When sharpening a scandi edge there will always be a slight convex to the bevel due to hand "rocking". So it is easy not to remove the burr fully at the end of the sharpening process before done or before next stone. Make sure you hit the apex wit the last one or two strokes, not a microbevel but "more towards the apex" stoke. A muddier stone as a last step helps too.

 

[yepimonfire]

Some softer steels seem to never take a complete usable edge without stroping to eliminate the bur in my experience. Even with 8k water stones.

 

[Obsessed with Edges]

For my own Helle folder, I spent time this evening working on it to grind the factory bevels to a crisp, complete apex. Lesson learned: the factory edge wasn't anywhere near a complete apex, AND it was apparently left with some weakened remnants (burrs, etc). Also, because the bevels on a scandi are so wide, there's a lot of metal that needs to come off, even to thin the factory edge a tiny bit. I did use a Coarse DMT to start the process, and that did do most of the work. I started to establish a hard & verifiable burr along the apex with the DMT; then used a SiC stone to take it further (discovering it's plenty aggressive enough that I could've started with it anyway); the SiC stone left a more attractive scratch pattern as well, and seemed to generate less of a burr along the edge by itself. Once I was confident the edge was truly apexed, I used two denim strops with AlOx compounds to clean up the burrs. One strop with Sears #2 compound, the other one had Ryobi white rouge. These worked BEAUTIFULLY in cleaning up the edge, and also worked quite fast to polish up the bevels, erasing much of the coarse scratch patterns left by the DMT and the SiC stone. I was glad to see that this blade has no trouble holding it's (apparently) 17°-19° inclusive edge after making some deep cuts into pine wood and still slicing up phonebook paper like a laser beam (& tree-topping arm hairs). I still don't know exactly what steel is used at the core of it's laminated stainless blade, but it takes an impressive edge. I was a little concerned I might over-strop it with the AlOx compounds, which are pretty aggressive, but the apex didn't round off at all; that seems to confirm the core steel is pretty hard (a vendor description of the knife says it's RC 58-59; that sounds reasonable).

After going through that with my scandi, I'd say it's not much of a stretch to assume these need a little more persistence in sharpening the factory edge to a full & crisp apex. Even though mine looked initially like it was very close, it still took quite a lot more grinding to really get it there. I'm a lot happier now, in seeing that a little more work got mine where I hoped it could be.


David

 

[HeavyHanded]

There's a lot of steel to be taken off when working Scandis down to a lower angle or even if just "flattening" out the existing angle.

I don't believe there is any common grinding media that produces a smaller burr for a given operation than good old SiC. After that, a waterstone works well in this role but is a function of how the grit pulls loose and works with a semi lapping action.

I was just tinkering with a soft 240 grit SiC jointer stone, timing how long it took to make my Old Hickory paring knife into a full blown, flat bevel Scandi. It takes patience - like fixing a poorly ground woodworking chisel, that's a lot of material to remove.

 

[awestib]

I used two denim strops with AlOx compounds to clean up the burrs.
David

Way to go David!
How do you attach the denim to your surface? Spray Glue? (sorry, no hitchhiking intended here!)

 

[Obsessed with Edges]

Way to go David!
How do you attach the denim to your surface? Spray Glue? (sorry, no hitchhiking intended here!)

One strop is my denim-over-HomeDepot-paint-stirring-stick (overuse of hyphens? ), and the other is denim-over-red oak (used to be leather, but I peeled that off the oak block). On the paint stick, I attached the denim with a strip of double-sided tape (very convenient), and on the other I used contact cement. I've mentioned using some spray adhesive before, and it should also work fine. I've been experimenting with different means to stick fabric or sandpaper to hard backing, and that's what influenced my choices. Any one method should work equally well. The bigger advantage of the spray adhesive I've used is in it's ability to be peeled off, when replacing worn sandpaper or trying a different material.

I still have some cleaning up to do, on the blade I mentioned. It's sharp as all get-out, but not quite as 'purty' as I'd like. Still need to work out some of the deeper scratches. It's a polished blade, and they're hard to ignore. But the cosmetics will always be secondary to making it sharp, so I don't mind too much.


David