RM Scandi sharpening question

[wentworth]

Hi All,
I'm sure we've all seen the Ray Mears sharpening segment either on the DVD or youtube. I can't tell if he raises the spine of the knife slightly to create a micro bevel using the car window, or if it is flat.

I've asked this elsewhere, but does a 4mm thick blade (with the geometry it has) need a microbevel, or would it turn my SWC into a prybar with limited cutting ability?

 

[poddle]

Its only a very light stroke, the angle is not that critical, its just to remove any wire edge that is left on the blade, but it would be better if you held the knife at a cutting angle.

 

[JonathanD]

The angle is roughly 45 to 50 degrees. When you do it though, you naturally hold it at the correct angle.

 

[HillBill]

Or you can use a honesteel. They are easier to carry than car windows..
Plus they are handy for sharpening a dulled edge too.

In fairness though, with the bevel angle on a woodlore/swc i doubt any micro bevel is needed, never had one though so don't quote me on that.

 

[wentworth]

Thanks all,
Hillbill, don't you make similar knives in 4mm?

 

[FGYT]

In fairness though, with the bevel angle on a woodlore/swc i doubt any micro bevel is needed, never had one though so don't quote me on that.

......................

 

[HillBill]

Thanks all,
Hillbill, don't you make similar knives in 4mm?

I use 3mm mate and a 22 degree grind, which i do add a microbevel to. A higher grind in thinner steel does need the microbevel for edge retention/toughness, but will cut deeper with less effort than a thicker blade with a lower grind like the woodlores.

 

[PeterHW]

IMO the Woodlore does need a slight convexing or microbevel after being sharpened flat.
If you check the DVD you will see RM says he does 50! YES 50! Strops on his belt on the edge .... this will induce a convexing of the edge and then he does a few passes on the car window to remove a wire edge ....probably produced from the stropping ....
not necessarily enough to give a distinct "flat" micro bevel but the convexing effect of 50 belt passes on the edge does actually take the "too fine" edge of the Woodlore down to a quite useful longer lasting edge and the car window probably just gives the edge "more bite" as Ray says ....

I have to say that every Scandi in O1 steel that I have .... both Woodlore/SWC and one by HillBill .... benefits from a slight convexing micro bevel applied once sharpened flat. I now apply this quicker and easier than the "50 passes" on the belt by using a leather stropping paddle ( the Bark River one ) with green chrome compound ... it only takes about 10 passes to get the same effect as using a none compound belt ... and then instead of the "car window" .... I use the white ceramic rods on the Sharpmaker set at the 30 degree back bevel setting and the triangular pinnacle position which is similar to the car window "curve" .... it only needs a few passes to give the edge the "toothiness" Ray talks about.

Doing a fine "convexing" strop applied micro bevel to a very fine flat ground edge is a common technique used in the USA on their competition cutting knives .... I spoke with Gayle Bradley about this when wanting to learn how they applied their edges .... and have to say it does give the very best "initial" cutting edge I have ever used. HillBill's knife in particular has done some very fine delicate shaving repairs on my GB SFA haft where "dinks" have needed sorting from catching the haft .... a scalpel could'nt have done a better job. Infact I posted a pic here of it making fuzz stick curls on one of my hairs .... so they do take a great edge like this .... but ....

I have to say though .... the edge "lasting" aspect of the Scandi design knives I have is not as long as I would like .... they cut like a "razor" with these edges .... and are marvellous initially on wood .... but some of the exercises RM carries out .... such as reaming a hole in a spoon handle for some cordage .... that type of work with the blade .... ground flat and sharpened as above .... does "roll" the edge near the tip.

Infact ... if you do a "training stick" ( a stick whittled with the various cuts needed in bushcraft wood work as per Mors Korchanski's (sp?) practise suggestions ) with any of my Scandi edged knives the edge on the blade has problems with "rolling" when working hard with your thumb on the spine to do the harder "pressure" cuts ....

Whereas .... if I do the work with other types of grind/edge combination the edge holds up better .... maybe not as initially sharp as a "scandi" done as per the above .... but certainly still "hair popping" sharp. The best grind for longevity I have used is an Asymetrical Grind ( convex one side and high flat grind on the other ) .... then a Convex .... then a Scandi with the micro convex bevel ... although the type of steel and Rc hardness of the edge does also play a part.

The "edge rolling" issue with the Scandi edges is something I would love to know if Ray has the same problem with .... I cannot see how he could'nt have the same thing happen .... it is one of the "big" questions I would love to ask him ... but there ya go ...

So ... to get back to your question .... I would definately put a convex micro bevel on your SWC knife .... it radically improves the edge .... and makes it at least last longer than it would without having one .... and you can experiment with the angle of the convex created when "stropping" .... but holding the blade just above the grind bevels works best for me .... that's probably around the 30 degree inclusive mark ... as the Sharpmaker can still take the wire edge off when set at that angle ....

 

[wentworth]

Thanks all.
I've been wondering why RM chose to put a scandi grind on such a chunky knife. I love my SWC and the aesthetics of the thick 4mm stock. But the strength of the knife seems somewhat offput by the fragility of the grind.

I understand that it's nice to have a knife you know is strong, but if the edge isn't going to hold up as well as the rest of the knife, is it worth it?

Any clues?

 

[Aussiepom]

Depends. They say "A chain is only as strong as its weakest link." But what's the purpose of the chain?

You have to consider for yourself what your priorities are and your main pattern of useage: Do you have a fine woodcarving instrument that happens to have a lot of extra, but redundant, strength built into the body of the blade and handle? Or do you have a general utility knife which has a weak link in its edge geometry? Or are you somewhere in between?

For what it's worth, a long time before this whole 'bushcraft' thing mushroomed in popularity, a reasonable edge geometry for a general purpose utility blade would have been considered as around 40 plus degrees, included angle.

Also, it's not the 'scandi' grind that's weak, that's just the name of a type of grind. It's the geometry of a grind that dictates whether it is weak or not.

Slightly off topic but, does size matter; a scandi grind with a secondary bevel? Doesn't that make it a sabre grind? Or doesn't a micro bevel count as a secondary bevel?

 

[wentworth]

I meant a zero grind scandi edge... which has far greater fragility, as it typically is acute. If the scandi was ground at a 80 degree angle, then no, it wouldn't be fragile. But they aren't.

 

[Aussiepom]

Hi Wentworth,

Yeah, I guessed that's what you were talking about, from the general content of the thread, hence my comment about a "fine woodcarving instrument."

I only made the other comment about the scandi grind just to highlight that sometimes I believe we are better off talking about edge geometries, rather than grind types.

ATB.