10 Degrees Per Side?

[db]

Isn’t the convex curvature what effects the edge cross section? Shallow curve thinner cross section and a larger curve a thicker one? Anyways all I can really report is I put a very shallow convex edge on my VG calypso and it’s been holding up very well. I don’t use sandpaper I put it on with bench hones by hand no jig. The bevel really starts right below the opening hole it’s fairly large with a shallow curvature. Best I can figure it looks like the angle at the very edge is around 12 13 degrees. I guess thinking about it when I do touch up sharpening I’m probably raising the angle each time because it only takes 1 or 2 strokes per side to bring back the sharpness. But I haven’t really thought about that until just now.

 

[CMSpeedy]

I got some slight chipping today after cutting cardboard boxes. The boxes were glued together and the glue probably did it. It is making me question the narrow angle grind. One day of hard work has made my edge ugly. The chipping has left a micro-serrated looking pattern on the blade. Should I put it on the Sharpmaker at 15 degrees to remove it. This will also put a bigger bevel at 15 which may help with the chipping. What do you guys think?

My blade is also getting very ugly looking. A 10 degree angle on a flat ground endura 4 produces a HUGE bevel. It goes almost all the way across the primary. I am thinking about sending it in to have the primary reground thinner by a few degrees. I would like to end up with a blade that cuts like a caly jr, but has the length of an Endura. To me this would be an ideal knife for what I do. It would be a dream in the kitchen for sure.

Who could do this for me? Would I need to have the blade rehardened and tempered? Is it a good idea? Can anyone here do it for me and also polish the whole blade?

 

[gud4u]

I was speaking of the general myth that the properties inherent in the convex bevel are due to the curvature and not simply the cross section.

Very well put, Cliff.

If we're considering just edge-strength: Every test I've made indicates that for hardwood-slicing with the steels I've tested, a final edge taper of 30 degrees provides adequate strength, whether it's applied as two 15 degree bevels, compound 10/15 bevels or convexed bevels.

The only reason I use 10 degree main bevels is for the general improved slicing performance - which has nothing to do with edge strength.

 

[sodak]

Sodak, thanks for your edge stories.
I wonder if you tried putting the same low 10 degrees on but did it free hand producing a convex bevel if the edges would hold up better? Maybe worth a try? It would make it a hair thicker behind the edge but I don't think it would be a noticeable difference in cutting, and may strenthin the edge a little wile still keeping the edge angle low.

I'm a *terrible* convex sharpener, but thanks for the suggestion. I'll probably keep sharpening at the same bevel through at least 3 more cycles, and if I'm still getting damage, put on a 15 microbevel and do a bunch more cutting with that. I'm hoping to go through a LOT of cardboard and wood in the next week or two, and see what happens.

 

[Cliff Stamp]

I'll probably keep sharpening at the same bevel through at least 3 more cycles, and if I'm still getting damage, put on a 15 microbevel and do a bunch more cutting with that.

I thought the Calypso Jr. was at 15 per side already? Or is this in reference to the D2 blades?

I got some slight chipping today after cutting cardboard boxes.

What size? Roughly how many meters of cardboard was cut? Less than 10, more than a 100?

Should I put it on the Sharpmaker at 15 degrees to remove it. This will also put a bigger bevel at 15 which may help with the chipping. What do you guys think?

Resharpening is likely to eliminate the problem, increasing the angle would likely help here as well. However the steel should not visibly get damaged cutting cardboard. You don't want to get into the habit of thickening edges to compensate for defective steel, assuming you are not hitting inclusions in the cardboard or cracking it through hardened epoxy. But even the latter seems difficult for me to accept because I have done hard plastic cutting with such profiles and heavy cutting of plywood and the edge will not get visibly damaged.

My blade is also getting very ugly looking. A 10 degree angle on a flat ground endura 4 produces a HUGE bevel. It goes almost all the way across the primary.

Yes, the primary is only a couple of degrees more acute.

I am thinking about sending it in to have the primary reground thinner by a few degrees.

In general you should always get the primary reground rather than reduce the edge angle. However as a user it is very difficult to do one and easy to do the other which is why people regrind edges.

Before you jump to the conclusion that the blade is defective, just see if the problem is removed with sharpening. Many times the initial edge on knives is made of weakened steel and removing it with sharpening makes the edge much more durable.

Every test I've made indicates that for hardwood-slicing with the steels I've tested, a final edge taper of 30 degrees provides adequate strength, whether it's applied as two 15 degree bevels, compound 10/15 bevels or convexed bevels.

The only reason I use 10 degree main bevels is for the general improved slicing performance - which has nothing to do with edge strength.

Yes, and yes. The problem is the posts like yours are vastly overshouted with makers constantly promoting "convexing" edges to make them more durable/cut better. The willingless of people to accept without critical thought always leads to the ability of misinformation to propogate rapidly. Ironically this is one thing the Bladeforums user base constantly complaints about with the non-knife people being "sheep" and just accepting the ideas of the goverment about the dangers of knife use/carry. The misinformation about convex edges will continue until a maker like Cashen takes a very public stance and tells people to look at the cross section and not the curvature.

Isn’t the convex curvature what effects the edge cross section?

A convex bevel simply means the curvature is above zero which is a flat bevel if it is negative then it is a hollow bevel. The bevel applied by the Edge Pro stones is going to be convex simply because the stones wear. Now it isn't very convex, the radius of the arc is very large, but it isn't perfectly flat. The problem is the common implication that the curvature itself is solving the problem which usually leads to some discussion (not here) of very incorrect physics to try and support this arguement. I could easily apply a convex bevel to a knife and make the edge stronger and cut worse, or weaker and cut better or even stronger and cut better or weaker and cut worse depending on how I applied the convex bevel.

-Cliff

 

[sodak]

I meant the D2, it was getting late (for me).....

 

[db]

I was unaware that people have been promoting the benefits of convexing is due to the curvature. I had thought it was a good and easy way to thin a knife. The reason I convex my knives anyways is it is easy to do by hand and doesn’t require anything but time and a stone. For me convexing is also much more injoyable to do compared to using a jig or some system. I like that I can get a knife really really sharp with nothing but a bench hone. So to me the benefits of convex blades are simple and quick will thin your blades and doesn’t require much you can even use sandpaper and a file if you want. Only real con I can think of is it is hard to really know what angle you put on but really I don’t care much what the angle is as long as it cuts better than it did before. If the edge chips I raise it a little or apply more of a curve. Not really knowing the angle makes it kind of hard to talk about over the net though.

 

[kel_aa]

Are you saying that a convex bevel is not thicker than a flat bevel when the edge is at the same angle? Is a thicker bevel not stronger, than a thinner one?

I had thought it [convexing] was a good and easy way to thin a knife.

Do you see a little contradiction there from your earlier post, Db?

 

[db]

No I sure don't think it is at all. Thinning a knife can be done by convexing, flat grinding, and hollow grinding. For me convexing is the easiest way to thin it out. Now try and stay with me here Kel aa. convex grinds are more thicker than flat grinds and flat grinds are thicker than hollow grinds, generel comments but true for the most part. Lets use a quote from Cliff maybe you will understand that better than me.
"
Cliff said...
A convex bevel simply means the curvature is above zero which is a flat bevel if it is negative then it is a hollow bevel.

 

[CMSpeedy]

Nobody has answered - Who can regrind my primary a few degrees thinner? At the same time I want the clip blasted. Also I think I want a different blade finish. Who could make this happen.

 

[kel_aa]

Db, I think I understand better where you are coming from. What you say is true when applied to the primary or relief grind. However, it doesn't apply in the same way to the actual edge. Having the same edge angle, a convex grind has to be thicker than an hollow grind. Conversely, having the same average angle, a convexed profile must have an greater edge angle. I illustrated second part:

The triangle and the convex shape both have the same average angle. The angle at the edge, however, is greater for the convex profile. (The logical extreme of this argument is that if the convex is of small enough radius, the then the edge takes on an 90 degree per side angle.) The converse of this statement is that to match the angle of a flat bevel, a convex edge must have less material and hence strength.

 

[Cliff Stamp]

Any custom maker could do a regrind on the primary, STR does really crisp grinds and also does really clean low ride clips + wave mods. Krein does really nice hollow grinds which are an option if you are using it for soft materials.

convex grinds are more thicker than flat grinds and flat grinds are thicker than hollow grinds

I would hope he doesn't stay with you on that as it is the exact basic myth which I noted in above which you then contended you never saw argued. The fact that the curvature is + or - doesn't imply anything about the cross section. As I noted you can convex an edge and make it stronger or weaker or cut better or cut worse or any combination of those, you can in fact do all of them at the same time.

A convex Opinel has a much thinner grind than a WB which is hollow. Busse's flat grinds are generally thicker than Dozier's hollow grinds. However Dozier's hollow grinds are are much thicker than Phil Wilson's flat grinds. TOP's hollow grinds are much thicker than BRK&T convex grinds however BRK&T convex grinds are much thicker than Johnston's hollow grinds.

-Cliff

 

[Cliff Stamp]

... to match the angle of a flat bevel, a convex edge must have less material and hence strength.

That is an interesting point of view. In general when you apply a relief grind, either by hollow/convex/flat, it doesn't matter, the edge bevel itself can be made more obtuse and the overall cutting ability still increase. This then makes the very edge more durable while the cutting ability has increased. You have of course also weakened it and made it thus less durable and more prone to rippling in high loading, and it now also cuts worse in very shallow cutting as Dave illustrated awhile ago. It is also complicated by the fact that the nature of the grind changes the loads the knife generally sees which is why you can regrind a large chopping blade or axe and have the edge durability increase and become less prone to rippling as the blade has better penetration and thus sees less shock on impact and better precision and control in hand.

-Cliff

 

[kel_aa]

Yes, the overall damage/wear resistance and cutting ability is more complicated. I was speaking of strength as an instrinsic quality of the material and geometry.

 

[Mtn Hawk]

Db, I challenge you to draw a convex grind on my template that has the same edge angle and is stronger (wider at some or all points) within the defined edge width. The one on the right is a multibevel grind as a 20 degree per side edge and 9 degree relief/primary grind.

Excellent question and drawing!!! :thumbup: (I see no one has answered)

I am glad to see a few people intelligently removing the fantasies about convex edges. I initially bought into convex edges, thinking from many posts I read that there was some kind of magic about them. It took quite awhile before I was able to separate fact from fiction. I'm not saying convex edges are bad things, just that there are trade-offs, like with almost everything else.

 

[kel_aa]

No one can do the geometric impossible.

I am glad to see a few people intelligently removing the fantasies about convex edges.

I don't think its magic, but its a good thing for the most part. For instance, if the most damage you see on your edge grind is only a portion of its depth, you can do with a thinner edge. For those who cannot or do not want to alter the primary grind, they can shave off some of the shoulder. Now you have 3 angles (or a curved shoulder), and that is just getting closer geometrically to a convex grind. As Cliff noted, the force distrubtion on the edge matches the strength of the convex profile better than a flat profile. I think the main objection for many (including myself) is that taking the knife to the stone will result in severe changes/scratches to the looks of the bevel and that the systems like the Sharpmaker can fairly easily give good edges with flat profiles.

 

[Cliff Stamp]

...the force distrubtion on the edge matches the strength of the convex profile better than a flat profile.

Yes, you are much better with multi-beveling than a single grind in general, this is the same issue of course as the typical scandinavian bevel vs a typical full grind with secondary edge bevel. The problem is too much promotion of convex bevels without any discussion of the nature of the grind and noted as gud4u commented that much the same can be done with just multiple flat bevels. In most of the cases of the mods done as in "I had the edge convexed" it would have been much better to have the primary flattened/hollowed than making a very wide bevel which needs to be sharpened.

-Cliff