What are your thoughts on reprofiling an RD9 to a scandi edge?

Noshtero

Noshtero

Joined
Oct 10, 2002
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I trying to decide if I should mess with my RD9. It's currently the large knife in my trio. The rest of the trio is a 4" scandi and a SAK.

I'm debating reprofiling the edge down to a zero edge scandi. It has the standard edge Justin puts on them right now, which is quite obtuse. Has anyone put a zero edge scandi grind on a large (9") blade before? Would it make the edge too weak to baton with? I do hold to the "right tool for right job" mentality, so the RD9 is pretty much reserved for splitting/chopping/clearing, that sort of thing. The brunt of my camp chores are done with the 4"er. Is there any reason to reprofile the edge? Is there any downfall to putting a hair popping edge on something used to chop? I've seen guys that could shave with their axes, after all.
 
Don't know. Interesting. If I were to reprofile it though, I'd go convex. Better for chopping.
 
The Rd9 seems too large for such a thin edge. But if you are a patient kind of guy, you could give it a go and see how it does. I think you'd be better off pushing the shoulders back (or get rid of them completely) and slightly reprofiling the edge.
 
Ranger knives are flatground right?

It would be impossible to do a scandi grind on them. You can't put metal back on:D

You could do a full flat grind or a convex.
 
I'm pretty much onboard with what Andy said. convexing is a bit more strong and efficient on a chopper. Also I'm having a really tough time envisioning the conversion of a full flat ground knife to Scandi....all I can envision is a really high delicate edge.

If you have a decent 1" belt sander your only minutes away from convex edged happiness! if all ya' got is some sand paper and a mouse pad....well...you're a good movie or two away from it...:D
 
I'm not overly versed on the different grinds, but the RD9 appears to have what I'll call a sabre grind on it. It's full flat back to the spine, but has a very pronounced secondary bevel on the edge. I also thought a sabre grind was essentially a scandi with a secondary bevel. What would a full flat with a secondary bevel be called? Am I correct in that a full flat is just a wedge, essentially? Head on it would be a perfect "V"?

If I were to try to take the full flat all the way to the edge, I would have to remove a ton of material wouldn't I? I was thinking perhaps I could just shallow out the secondary bevel a good inch back off the edge. It would look like a scandi, except the main blade body would be slightly beveled.

Here's some expertly drawn pictures to help illustrate!!!
The first one is what it looks like now. Full flat, with a secondary bevel.
The second one is kinda what I was thinking. Pull that bevel way back.
The third one is what I would assume a convex edge would look like.
edges.gif


I'll admit I've never tried sharpening a convex edge. I keep about a mousepad, but honestly would have no idea what I was doing. I would most likely send the knife to Justin at Ranger to do the reprofiling anyway, so I would just need to worry about sharpening (I have no belt sanders/grinders/patience to do it by hand).
 
Nice...Thanks William.M

So to reprofile this guy convex all I'm essentially doing is rounding the shoulders right? The advantage here is after the initial bevel is in the material, the rounded shoulders don't catch on the walls of the cut as badly as sqaured shoulders would, thus making it continue through the material with less drag?

Sorry for my ignorance. I always thought I could learn one edge geometry and never stray from it. Hence the majority of my knifes are scandi edge.
 
It sounds as though you need some material removed above the edge. In other words the entire grind needs to be thinned especially just above the cutting edge. If the main grind is too thick above the edge, it doesn't matter what edge type you have it will still not cut as well.
Scott
 
As suggested, I'd try removing some of the shoulder to create a more acute convex or flat secondary bevel.

A single bevel, assuming that is what you ask about, would be relatively weak in a big, chopping knife. From the professional wood-carvers knives I have collected, it's apparently too weak for wood-carving. (They were all convex edged.)
 
my rd7 was custom ground, but i believe that justin uses a full flat grind with convex edges on the production units as well. a true scandi, as others have mentioned, isn't possible. if you want a thinner edge for better cutting, it's possible. but as you have mentioned, your 4 inch blade handles most camp chores and the rd9 is for the heavier stuff. i would keep it as is and just keep a scary sharp convex edge on it. i've used my quite hard and haven't had any chipping or rolling, which you would probably encounter with a thinned out edge.
 
In addition to what others have said, the Scandi grind is a very poor choice for a heavy chopper type knife. It's an excellent if not the very best grind for woodworking knives, but it's more prone to damage than most other grinds. For a chopper, I'd go with a flat grind or convex.
 
My RD9 has what I guess you can call variable edge. flat and narrow the first 3-4" for finer controlled cutting ,tapering out to a slightly thicker edge in the chopping zone.Works great, no dammage to the thinner zone yet even with battoning. Worse thing could happen would be obtaining a slight recurve from removing any chipping or dulling through excesive sharpining, wich I wouldnt mind one bit. But, i think that would take a long time with an RD9. I use a 6" diamond bench for the narrow flat zone and butcher steel the rest with the diamondstick.
 
Elen said:
In addition to what others have said, the Scandi grind is a very poor choice for a heavy chopper type knife. It's an excellent if not the very best grind for woodworking knives, but it's more prone to damage than most other grinds. For a chopper, I'd go with a flat grind or convex.
Click to expand...

I tend to think a Scandi grind isn't a poor choice, let alone very poor choice. But it may depend on the thickness of the blade stock. A Tramontina machete comes with something close to a Scandi grind. However, they're stamped from steel less than 1/8" thick. With thicker blades, I'd think a Scandi grind would get much less efficient at slicing, but relatively strong for chopping. Convexing may be advantageous regarding sticking while chopping, but no inherent advantage of strength.

But it's all a moot point, as the RD series don't seem really capable of really being re-ground as Scandis.
 
Others have already said this, so I am just summarizing and adding my opinion.

It sounds like you are just confusing grind terminology a bit. Since the RD9 has a sabre grind, it can not have a scandi grind too. It is too late for that. What you do have is a sabre grind with a secondary bevel. The secondary bevel sounds too thick (obtuse) for your taste.

I personally believe that a bigger chopper can handle a thinner edge than what you have, but you don't want to go overboard. Both my large knives and small axes (hatchets) can shave hair, but are not as scary sharp as my 4 inch sized knives.

If you want to thin that edge, you have to options:
1) V-grind it back. Sharpen at less angle just to remove some bevel metal and make it sharper. You could also do a multi-stage v-grind. Have 15 degree per side transition into 20 degree per side for the final edge. 20 degree per side should be plenty sharp, but as you move further up the edge, the 15 degree per side can increase cutability.
2) Convex it. That is what I would personally do. And the way I would do it is multiple angles on belt sander until I got a convex edge I wanted. I do that sort of thing by eye. I would then put a high polish on it.

A high polish on an edge used for chopping is more durable. It seems counter intuitive, but it is true. I used to think "why should I spend so much time polishing an edge I am just going to chop with." But, sharpening creates little micro-teeth on the edge. If the edge is coarse, there are few of them. A single one (or couple) is likely to take a larger impact from a chopping blow. On a highly polished edge, the impact will be spread over MANY really fine teeth, lessening the damage to any single one.

Hope that helps.
 
We absolutely have terminology issues.

Most "scandi ground" knives are saber (sabre) ground with a "single bevel" (on each side, of course). How acute the resulting "V" is depends on how high the single bevel begins and how thick the stock is.

However, since the essense of a "Scandi" is that there is no secondary bevel, you can get the same effect in terms of use and sharpening (lay the bevel flat on the stone and grind away) with a flat-ground knife with no secondary bevel -- just a single V from the spine to the ultimate cutting edge.

Some RD-9's have a saber grind and some have a flat grind.
 
Ya my bad on confusing everyone. I don't really consider the body of the blade back to the spine as part of the "grind", so right now I have a full flat grind with a secondary convex bevel on the edge. When I said regrind it to a scandi grind, what I meant was make it a very deep sabre grind. Regardless of if the body behind the scandi grind is unbeveled, or slighty beveled because it used to be full flat, the "scandi" grind to me is that it has a deep single bevel to the edge. I'm sure that makes some of you cringe :)

I'll go convex as recommended here. It's that already, but I may bring the shoulders back a bit and polish it up.

Thanks guys!
 
Since I found Noshtero's post very confusing I won't try to comment directly.

I think high quality choppers like Scrapyard, Ranger etc can do with a less obtuse edge.
I found with my coated Scrapers that even thinning the coating near the edge helped.
Cutting competition bowies are essentially knives like the RD9 with a very fine sharp edge.
I would not go as far as a cutting comp blade but moing the shoulders back and thinning the edge is going to make quite a difference.

A convex edge should look like an appleseed.
 
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