Lets argue about knife grinds . L:O:L

[Kevin the grey]

I posted this on another forum . I think it also belongs here seeing as we are so active as to knife useage .
I was given a becker necker and I have been putting it through its paces . Loits of chopping , battoning and I even took down a small tree with it . The blade is shaving sharp and fairly easy to bring back after an afternoons work . I tried whittling with it or even scraping with it and it fought me all the way . It has a thick blade with a flat grind and a very obtuse edge . Is this edge obtuse to make up for a softer steel or is it just an edge designed to survive rough work ? I would like to make the angle slightly more acute and use it as a second bevel of a 15 degree edge . I want a camp tool that is a bit more versatile as to scraping/whittling.carving handles and what-not .Am I on the right track ?

 

[Ghost93]

I Have found that on my RSK Mk 1 I droped it to 17 degrees per side and does alright with woodwork, although my moras and my BRKT North Star tear through wood like a hot knife through butter. The Moras are scandi grind, which has second becel and makes for excellent carving although strength is somewhat lost, but dont be fooled into thinking the mora is an inferior blade. My North Star has a convex grind which also is great for wood work. It is also a bit stronger grind than scandi, depending on how it was ground, thick or not. I generally like convex grinds better than others due to ease of sharping and a good all around edge (just don't let it get too dull). I wonder if Cliff will grace use with what he thinks?

 

[kel_aa]

What angle is it at right now? From the company picture, the primary grind doesn't look to bad. It certainly looks much better than a Kabar, and many people make do with those. Do you think transfering power from the grip to the blade is an issue? The handle doesn't look too comfortable.

With 15 degrees, Cliff says you should be able to chop caribou bones with no damage!

 

[Kevin the grey]

I have very small hands and even I find the handle a little small . Maybe I,ll put two layers of cord on instead of one and see if it feels better bulked out . I do not think it is a question of power as I can still apply quite a bit . It just does not go anywhere in a piece of wood . Don,t get me wrong . I am more than satisfied with the knife so far . I am just wondering what results I would get if I changed the angle . Also this was a gift to me of a used blade . It might have been reground by the previous owner .

 

[Cliff Stamp]

From the company picture, the primary grind doesn't look to bad.

It looks high enough but it could be too shallow there is no way to tell from the picture. Consider that you could for example do a full height primary grind of 0.5 degrees and leave the edge at almost full stock thickness, this iextrme sn't the case here but the edge could be far too thick and difficult to see in a picture. I wish manufacturers would cite the edge specifications, thickness and angle, and level of finish.

With 15 degrees, Cliff says you should be able to chop caribou bones with no damage!

Edges have taken a massive jump in the last generation in terms of thickness and angle, incidently there has also been a rise of stainless steel in cutlery. For reference to angles on impact blades consider that a full size felling axe, not made for softwoods, has an edge of about 15 degrees only in the last 1/16" of the bit, it quickly sweeps down to under half of that. It would seem unlikely that a small neck knife for wood working would need a similar angle.

I have very small hands and even I find the handle a little small .

This is a common problem with really small knives, cutting the handle back can really reduce functionality, a half and inch to an inch can easily cut the overall performance back to a small fraction. It always seemed to be to be a waste unless the knife was made purely for precision work so had a tiny blade out of very thin steel and very hard steel.

I am just wondering what results I would get if I changed the angle .

Generally between a linear and cubic increase. You pick up one multplier due to the direct decrease in wedging forces which are proportional to thickness, and you get another one from other effects such as fatigue which can be slight to very strong depending on how you carve. The typical scandinavian angles of 9 to 11 degrees for example will carve woods significantly better than two to one over the common 20 degree bevels found on most knives.

For impact tools you will also pick up a multiplier from issues of vibration transfer, chip clearing ability, etc. . Then there are other issues like gains in control and precision and the ability to obtain a higher slicing aggression at a given finish. There is also an overall increase in ease of sharpening as acute edge angles magnify the effects of sharpness at a given quality of finish. It is trivial for example to get a 5 degree edge to shave compared on one at 25 degrees. You can pretty much do the former by accident because the cutting ability is so high that it influences almost any measure of sharpness.

The only real concern is the width of the edge, if it gets really wide then it starts to have drawbacks, but in general these are slight compared to the gains unless you jig sharpen, but you can compenstate by use of micro-beveling.

-Cliff

 

[Kevin the grey]

Cliff I think that is exactly it . The blade cuts into the wood well for a fraction and then stops like it hit a wall . Even when arm shaving sharp . Really i think I have to start at zero . I think this must include reading a book . I,m not rich at all right now so I will have to look around for something inexpensive . I have good hands and picked up sharpening fundamentals mostly from trial and error . Considering I wish to achieve more with blades than I am capable now it is time for me to learn more .

As for length of handle ? I agree in general . Not in this specific case . I have blades with smaller handles that feel better in my hand . I,m 6 foot 1 250 pounds and I ahve never seen hands as small as mine on anyone . Its good for working with small electronics and hell when it comes to puting grip power on something . I think if I flesh out the handle and change the edge it will make a lot of difference .

 

[RokJok]

... start at zero . I think this must include reading a book . I,m not rich at all right now so I will have to look around for something inexpensive.

Use your local library. Since the cost of checking out books is free, the price is right.

Sharpening is a hot topic these days, in both the knife and woodworking tool worlds. Consequently, it seems there has been a bunch of books released recently on the subject. Check the library catalog for "The Razor Edge Book of Sharpening" by John Juranitch or Leonard Lee's book on sharpening. There may be other books that would help you out, but those are the two that leap to mind as the most often recommended.

 

[Cliff Stamp]

Sharpness is essential for a knife to cut well on most materials however on a lot of materials it doesn't determine the largest component of the force required for a blade to cut through something. A Mora 2000 for example can be *much* duller than a Strider WB and still cut much better on woods because the cross section of the Mora is significantly lower. The cheapest blades to check for optimal cutting performance are Opinels.

Opinels have full grinds on very thin stock and taper to very fine edges, essentially micro-bevels, they are often sharpened full from the spine to the edge with no distinct secondary bevel. The inexpensive scandinavian blades from Ragweed Forge also offer very high cutting performance for your dollar but the low grind will put them significantly behind Opinels. The acute edge though will still make them out cut many modern knives with stock edge profiles aside from some of the thinner Spyderco's like the Calypso Jr. which has the same edge angle and a high primary grind.

In terms of general performance, a higher sharpness allows the knife to start a cut easier and a more efficient geometry allows the bulk of the knife to move through the material easier. The next consideration is efficiency of force transfer from you to the knife and this has to do with leverage and ergonomic and security aspects of the grip, as well as weight and balance for dynamic cutting like chopping.

-Cliff

 

[Kevin the grey]

Just to focus on one small part ? Concerning Opinel and Mora . There must be a downside to the thinner grind ? AS in wearing out the blade faster or fragility ?

 

[Cliff Stamp]

Strength goes down very fast with cross section, basically quadratic with thickness and stiffness is cubic. For wood working there are two main concerns. The main cutting one is that the edge when very acute can turn when chisel cutting with a baton through heavy knots. The more experience you have here the worse wood you can cut because keeping the blade stable and not turning is a major influence on the resistance to rippling. The biggest concern in generalis lack of prying ability because these blades are so weak that you can easily crack them off by just flexing your wrist so they are limited in how much force you can apply and thus more robust blade patterns can be more effective in breaking apart dead woods and other tasks which benefit from high strength. There is also the issue of low weight for dynamic cutting like chopping as these blades are so light than even removing branches is inefficient and something like the Manix is many to one times faster.

-Cliff

 

[Kevin the grey]

I,m going to go to the library as suggested and throw some titles at you . I read a lot but I like it to have as much value as possible .

 

[mr.trooper]

HIGH SABER GRIND!

Im a High Saber Grind man!

High Saber grind, Saber grind saber high grind, high saber grind!

 

[Kevin the grey]

HIGH SABER GRIND!

Im a High Saber Grind man!

High Saber grind, Saber grind saber high grind, high saber grind!

I,m not sure what your preference is .
Could you be a little stronger in your opinion ? L:O:L

 

[shotgunner11]

This thread is a great chance for some of us novices to pick up some basics on blade grinds and optimum angles and the like.

I have found the full flat grind of my Spyderco Manix is amazing on most materials. What are some of the other names for this style?

I really like the grind on my Beckers for chopping and general heavy work. What grind is this and what other names would it go by?

If the Manix is a full flat with a 1" blade width, would a knife with a 2" blade width and a high flat grind have similar performance?

Its all really complex to someone just starting out, even though its a second language to alot of us here. I can remember trying fruitlessly to unravel some of Cliff's post in my head when I was really wet behind the ears, now I'm just pleasently moist behind the ears and am only confused MOST of the time.

 

[Cliff Stamp]

I have found the full flat grind of my Spyderco Manix is amazing on most materials. What are some of the other names for this style?

Full flat grinds are usually just abreviated to flat grinds.

I really like the grind on my Beckers for chopping and general heavy work. What grind is this and what other names would it go by?

The Beckers are flat grinds of varying height. Some are shallow that they are usually called sabre grinds like the Brute, some are so high they are usually just called flat grinds like on the Magnum Camp.

If the Manix is a full flat with a 1" blade width, would a knife with a 2" blade width and a high flat grind have similar performance?

If you scaled up the thickness so the same angle was cut by the primary grind then yes the cutting ability would be similar in some ways. However since the blade is wider it becomes harder to turn in cuts and you will notice this immediately if you try to peel a apple with both. You can see the same effect in carving turns in wood. There are other issues as well such as the increased weight and the greater binding in deeper cuts once you go above 1" in penetration on rigid materials.

-Cliff