Insane performance boost in cutting ability!

[HeavyHanded]

The Scandi will generally have a much stronger tip than a knife with a thinner grind. For drilling in wood, it is about the best solution you could come up with at the end of a blade. The larger bevel and subsequent wider spread is also very good at separating wood along the grain lines. Is also very easy to maintain stable geometry as the knife is resharpened.

Is not a very good solution for general knife work, but is a very good solution for a woodworking knife that can still do general chores reasonably well. The ones with thinner spine and higher grinds tend to perform better for general work that ones that have relatively thick spines.

This is the puukko I carry most that has a Scandi grind - it performs pretty well for day to day stuff and is extremely strong. The edge also tends to perform well even when dulled.

 

[tinkerer]

So, I have a new blade that could benefit from a reprofile to reduce the edge width. Its jsut a little too thick for my taste.

Have we come to a decision? Power or by hand only. Is the micro heating enough to actually damage the blade or edge, or is it removed during sanding and sharpening?

I can do either, but would prefer power as I do have 3 other jobs. I am thinking power (1X30 with a 100 belt) for the major work, hand sanding for final shaping, and hand sharpening.

Larry
Tinkerer

 

[me2]

Any idea of the edge angle on that one HH?

 

[HeavyHanded]

Any idea of the edge angle on that one HH?

At the edge its 24 inclusive, maybe a degree or two lower at the shoulder as it has a very slight convex across the face. That's pretty much the way it came to me from the factory. The spine is .125" and overall width is 7/8" at widest point. If I get sloppy it might open up to 26 or so after a bunch of touch-ups, never more than that. This is the same knife I photo'd and reconditioned on my Washboard after a month and a half of use, including a camping trip and a fair amount of daily use. Was still pretty sharp for regular use, due in large part to the acute edge, though couldn't even shave arm hair along most of its length.

While Scandi are maybe not the best all around pattern, it is a heck of a solution for a smaller knife.

 

[REK Knives]

So, I have a new blade that could benefit from a reprofile to reduce the edge width. Its jsut a little too thick for my taste.

Have we come to a decision? Power or by hand only. Is the micro heating enough to actually damage the blade or edge, or is it removed during sanding and sharpening?

I can do either, but would prefer power as I do have 3 other jobs. I am thinking power (1X30 with a 100 belt) for the major work, hand sanding for final shaping, and hand sharpening.

Larry
Tinkerer

If you do powered ideally you would want some type of liquid cooled set up. But you can probably get away with doing the majority of reprofiling on a rough new belt, just don't get too close to the apex (maybe .020" thick). Then you can finish it out by hand.

 

[tinkerer]

OK, belt sander it is.

You have no idea how much trepidation I approach this with.

The blade is done, mirror polished, and the edge nicely finished, but fairly massive.

So I will be taking my time, dunking frequently, and making sure I don't burn anything or destroy my lines.

Larry
Tinkerer

 

[chiral.grolim]

So here is a newer Buck 301 as received from the factory. The springs are weak on this model and the grinds so thick (all 3 >0.020") that the blades bind and then close readily when trying to back-out of the cut :thumbdn:

I did some grinding (80, 120 grit on a 1x30, followed by some hand polishing at ~800 & 2000 grit, I may go back and hand-grind and polish-out the scratches later... maybe) - edges are now 0 for the spey (scalpel), <0.010 on the main-blade, ~0.015 on the sheepsfoot (carver) with asymmetry.

Blade-binding is now a thing of the past and sharpening is much easier. I haven't had any durability issues, but I restrict the use of each blade to its geometry. Like I said, I may polish it further but this is a user and I still have my Rodent 9 to get to...

 

[REK Knives]

Blade-binding is now a thing of the past and sharpening is much easier. I haven't had any durability issues, but I restrict the use of each blade to its geometry. Like I said, I may polish it further but this is a user and I still have my Rodent 9 to get to...

Thanks for sharing man! That is great work!

I like how you changed the geometry up for each blade so you have a range of uses all built into that one knife. Great idea!

 

[REK Knives]

I just put the finishing touches on this bad boy w/ a zero grind... Fernando Medina did the rest (not sure if he's on this forum)

[video=youtube;lnFqGroR3PY]https://www.youtube.com/watch?v=lnFqGroR3PY[/video]

 

[KennyB]

John Juranitch emphasizes this important principle in his book, "The Razor Edge Book of Sharpening". I'll see if I can find the direct quote, but at one point he suggests that a blade 1" wide should measure under .020" in thickness, at the area of the blade 1/4" up from the edge to the spine... If that makes any sense. I've found that this isn't very easily done though, as having .020" thickness 1/4" away from the cutting edge means a really thin blade stock. I think he was talking more about butcher knives with very thin spines.

Does anyone have a stock measurement of the Izula's thickness behind the edge? I have two of them but I reground a long time ago so not sure what it is originally. I'm interested in where along the blade one should measure thickness though.

The top one (stainless Izula) I back-beleved to 11 dps and then put a small 15 dps micro-bevel on. The bottom one is done pretty similarly, except I convexed it from 11 dps on up and put a 18 dps edge bevel on it.

As you can see I've ground off a lot of the original blade material on the carbon one. The stainless one I Just got in December and the only grind work has been to put on the back-bevel and new edge.

Stainless thickness behind the edge: .030" + .005" (For those that aren't familiar with tolerances, that means the lowest measure was .030" and all others were .005" or less above that )
Carbon Izula thickness behind the edge: .030" + .010"

Measuring the thickness on the carbon one was a bit tougher because the bevel shoulder kind of blends in with the rest of the blade but I tried to find it the best I could based on the grind marks left.

The thing I'm wondering, should I really be measuring the thickness at the bevel shoulder, and if so which bevel? The primary cutting bevel's shoulder, or the back-bevel's shoulder? As you can see on the carbon Izula, the primary cutting bevel is much larger (in terms of width ) than the micro-bevel on the stainless one. But they're both similar thickness at the same point along the blade (~.100" up from the edge) , so I think that's a better point of comparison.

So that being said, if one were going to compare a stock Izula to mine, and they measured at the bevel shoulder... Then the stock Izula's bevel shoulder is going to be much closer to the edge. More like .050" away from the edge, and thus further down the blade stock where it is thinner. So invariably, if you measure the stock knife at the bevel shoulder, it will read thinner than measuring a ground knife at its new bevel shoulder. So if instead of measuring the thickness of the stainless Izula at the bevel shoulder, if I measure it at about .050" up from the very edge it measures .020" and under.

So should we really be measuring thickness at the bevel shoulder, or at a fixed point away from the very edge?

Am I making any sense?

 

[Fred.Rowe]

A blade ground with a prominent distal taper would have a huge difference depending on where, along the edge, the thickness was measured. So even though its the shoulders thickness that affects cutting ability, with identical apexes its edge angles that need to be compared. Blades with prominent distal taper don't have even primary bevels along their length. I grind primary bevels with known angles but at the end I'm doing alterations when I get to the radius behind the tip.

Fred

 

[chiral.grolim]

Does anyone have a stock measurement of the Izula's thickness behind the edge?
...
Stainless thickness behind the edge: .030" + .005" (For those that aren't familiar with tolerances, that means the lowest measure was .030" and all others were .005" or less above that )
Carbon Izula thickness behind the edge: .030" + .010"

...

The thing I'm wondering, should I really be measuring the thickness at the bevel shoulder, and if so which bevel? The primary cutting bevel's shoulder, or the back-bevel's shoulder?

...

So should we really be measuring thickness at the bevel shoulder, or at a fixed point away from the very edge?

Am I making any sense?

My Izula measured that same 0.030"+/-.005 at the shoulder before I took it down slightly to 15-dps. The primary bevel on most of these knives is 5-dps so slight alterations at the edge to widen the edge-bevel don't impact edge-thickness all that much. For uniformity of measurement, taking the thickness at the shoulder behind an apex of a standard edge-angle 15-20 dps tells us also how far back from the edge the measurement was taken, as the height of a bevel 30-degrees inclusive is 2X the thickness.

The only part where you didn't make sense is with the term "primary cutting bevel" - Is there a "secondary cutting bevel"??? There is not. The "primary bevel" is the main grind of the blade, usually ~5-dps, then there is the "edge bevel" or secondary grind up to the apex, i.e. what you sharpen. You can also add a "back bevel" as "tertiary" or whathaveyou, just so long as you differentiate the "primary" bevel as the main grind and the "edge bevel" to the cutting edge.

 

[REK Knives]

Blades with prominent distal taper don't have even primary bevels along their length.
Fred

Fred, not sure I understand this part... could you explain further?

Here's a SnG I just finished up...

 

[KennyB]

My Izula measured that same 0.030"+/-.005 at the shoulder before I took it down slightly to 15-dps. The primary bevel on most of these knives is 5-dps so slight alterations at the edge to widen the edge-bevel don't impact edge-thickness all that much. For uniformity of measurement, taking the thickness at the shoulder behind an apex of a standard edge-angle 15-20 dps tells us also how far back from the edge the measurement was taken, as the height of a bevel 30-degrees inclusive is 2X the thickness.

The only part where you didn't make sense is with the term "primary cutting bevel" - Is there a "secondary cutting bevel"??? There is not. The "primary bevel" is the main grind of the blade, usually ~5-dps, then there is the "edge bevel" or secondary grind up to the apex, i.e. what you sharpen. You can also add a "back bevel" as "tertiary" or whathaveyou, just so long as you differentiate the "primary" bevel as the main grind and the "edge bevel" to the cutting edge.

I guess what I'm trying to point out is that I'm not so sure you can correctly infer the thickness of the blade at a spot further away from the edge with just the thickness behind the edge-bevel's shoulder, because of the angle change that happens with a back-bevel. So for example you were saying that the height of a 30 degree bevel is 2x the thickness... So if a person measured the thickness of a .050" wide bevel sharpened at an angle of 30 degrees, and it was .020" thick, then if they measured that bevel .100" up from the edge, it would be at .040"...

But what if it's resting on a back-bevel of 22 degrees? Plus on top of that, the edge-bevel on my stainless Izula for example is so small that if I were to measure the thickness of the edge behind that bevel's shoulder, it would be <.005" which is a tad bit misleading since if I measure at the back-bevel's shoulder it's the .030" figure I mentioned.

So I guess another way to phrase my question is... If someone claims that their edge is .005" behind the shoulder, how do we know they're not just measuring a portion of the blade that is so close to the edge that it skews the result? A person might take the same knife, but with a much wider bevel and measure it, and get a much larger measurement because they're measuring further up the blade stock...

 

[Fred.Rowe]

Fred, not sure I understand this part... could you explain further?

Here's a SnG I just finished up...

Hi Josh,

Those are some nice looking bevels.

I was referring to the actual geometry of a blade ground with full distal taper where the blade's spine is at full thickness at the plunge and then narrows as it goes toward the tip. If the spine is say 1/4" at the plunge and then goes to zero at the tip the bevels aren't actually being maintained at the same angle from plunge to tip. There is some cheating going on to make the bevels appear flat and equal. I grind a lot of big knives with long distal taper using a Bubble Jig, which helps to maintain the bevel grind to close angle tolerance. In order to maintain the appearance of flat bevels the angle needs to be made more acute. If this isn't done you end up with a "bulge" just behind the tip of the blade. I heard someone refer to this as feathering and this is probably as good a term as any.
A knife that doesn't have distal taper does not have this issue other than at the tip.

Regards, Fred

 

[REK Knives]

Hi Josh,

Those are some nice looking bevels.

I was referring to the actual geometry of a blade ground with full distal taper where the blade's spine is at full thickness at the plunge and then narrows as it goes toward the tip. If the spine is say 1/4" at the plunge and then goes to zero at the tip the bevels aren't actually being maintained at the same angle from plunge to tip. There is some cheating going on to make the bevels appear flat and equal. I grind a lot of big knives with long distal taper using a Bubble Jig, which helps to maintain the bevel grind to close angle tolerance. In order to maintain the appearance of flat bevels the angle needs to be made more acute. If this isn't done you end up with a "bulge" just behind the tip of the blade. I heard someone refer to this as feathering and this is probably as good a term as any.
A knife that doesn't have distal taper does not have this issue other than at the tip.

Regards, Fred

Great Fred, thanks for the explanation!

 

[chiral.grolim]

I guess what I'm trying to point out is that I'm not so sure you can correctly infer the thickness of the blade at a spot further away from the edge with just the thickness behind the edge-bevel's shoulder, because of the angle change that happens with a back-bevel. So for example you were saying that the height of a 30 degree bevel is 2x the thickness... So if a person measured the thickness of a .050" wide bevel sharpened at an angle of 30 degrees, and it was .020" thick, then if they measured that bevel .100" up from the edge, it would be at .040"...

But what if it's resting on a back-bevel of 22 degrees? Plus on top of that, the edge-bevel on my stainless Izula for example is so small that if I were to measure the thickness of the edge behind that bevel's shoulder, it would be <.005" which is a tad bit misleading since if I measure at the back-bevel's shoulder it's the .030" figure I mentioned.

So I guess another way to phrase my question is... If someone claims that their edge is .005" behind the shoulder, how do we know they're not just measuring a portion of the blade that is so close to the edge that it skews the result? A person might take the same knife, but with a much wider bevel and measure it, and get a much larger measurement because they're measuring further up the blade stock...

In post#2 of this thread, I presented a back-beveled Muela that I took from 0.035" down to 0.010" behind a 15-dps edge. Obviously those measurements were taken from shoulders that weren't the same distance back form the apex, but both were taken from the same transition point, i.e. a dramatic change in geometry from a 15-dps edge to 5-dps primary, giving a complete picture of both bevel height as well as thickness. If i were to present a measurement from somewhere within the bevel, that is not an accurate representation of the blade's geometry as it does not give the bevel height, hence the first example is moot.

As to the second example, the more complex the geometry of the blade, the more data required to give a complete picture of the actual geometry. Ideally, one would know the width and thickness behind each bevel in order to generate a complete schematic of the blade cross-section. Commonly there are only 2 bevels - primary and edge - to evaluate, but with back-bevels and convex bevels, it can be harder to determine the point of transition at which to measure the height and thickness of the edge-bevel. For example, the schematic below compares a convex zero-edge BRKT Bravo 1 to two knives with traditional primary and secondary bevels.

Where would you measure the thickness of the Bravo1 edge? You would not measure it at all, it is a "zero-grind", i.e. zero thickness behind the edge. HOWEVER as soon as you grind/sharpen the edge to produce a secondary bevel, even if a convex one, you should be able to take a measurement at the rounded transition from the primary angle to the edge-angle - you present a measurement that accurately approximates the geometry of the edge.
For the Izula you mentioned, the "microbevel" thickness isn't valuable information and it will be eradicated on the first sharpening as the new bevel cuts into your back-bevel which is still quite steep at 22-inclusive and not much different from 30-inclusive (only 26% reduction). In comparison, if you maintain that back-bevel - grinding down to the apex and then adding a 30-inclusive microbevel with a few quick swipes of the hone - the thickness behind the back-bevel will only increase marginally with each sharpening in accordance with the low primary angle that is ~10 inclusive (full 60% reduction in angle). Thus, the honest presentation of your Izula's geometry is to give the thickness in front of the primary bevel as "0.030" behind the edge at 22 inclusive with a 30-inclusive microbevel".
On my Muela, the back bevel is 5-dps, i.e. what the primary would be if lifted from the hollow (as seen by the grind-marks at the height of the primary). If I gave the thickness behind my back-bevel, it wouldn't be much more than the thickness in front and would also not accurately represent the height of the 15-dps edge. The back-bevel in this example can be thought of as an extension forward of the primary, if i blended the scratch pattern you wouldn't even know it is there. But a back bevel that is only slightly reduced from the edge-bevel (30 down to 22) is more like a back-extension of the edge-bevel. Make sense?

 

[REK Knives]

Here's one I finished up earlier today! This knife is going to be used for skinning deer and such so I left the tip thicker on purpose for getting in the joints. Man was this edge thick prior to the regrind! I'm surprised it cut anything.

 

[FlameCycle]

razor-edge-knives, I really want to thank you for making this thread. It has really opened my eyes about the performance of blades.

For a while I have been having a hard time putting my finger on what was bothering me about several knives. I began stepping up my sharpening game but still kept being disappointed. For eg I have an esee 4 that I put a great scary 15dps edge on, but the damn thing still feels like it cuts like a pry bar. Id guess it's at least .030 behind the edge, maybe more. Also I was internally struggling with the fact that my mora (scandi) had such a low inclusive angle, yet didn't seem to slice food all that well even when razor sharp. Plus I didn't know why my spyderco caly3 cut so much better than my tenacious even though they were both the same sound thickness with ffg primary and 15dps secondary bevels.

It all seems so obvious now as I think about it in the context of this thread's discission. The caly is ground much thinner behind the edge than the tenacious. Knives like the esee and mora won't turn into good slicers just because I put a good edge on them - I feel dumb for just grasping this concept now. On the other hand I think there's a pretty big contingent of other knife fanatics who haven't quite figured this out either.

Anyways, thanks. Now I have to knock the shoulders of the esee and tenacious way way back and see if I can improve performance without a full regrind.

 

[REK Knives]

Hehe, you're welcome bud! Glad it helped... yeah see if you can take the shoulders lower, like 10 dps and then micro bevel at 15. Should help a bunch!