are all Buck knives their 420HC

[Obsessed with Edges]

(...) I've noticed that when carving, my 440C Bucks hold an edge longer than my 420HC Bucks and carbon steel knives, but I can't restore the 440C blades with stropping alone like I can with the 420HC and carbon steel. I can bring back the 440C blades by touching them up with 600 grit stone (Lansky - Back bevel is 17 degrees and cutting edge is 20)

Is the likely scenario that the old 440C was tempered too hard (becomes brittle) and that this combined with a 20 edge and wood carving is causing the edge to fracture, thus requiring stone sharpening to restore?

Or it more likely that the that edge is folding and that my stropping technique & compound need to be improved to be able to realign 440C (even though I can with 420HC and carbon)?

Thanks for any insight you could shed.

The difference in edge-holding can be attributed to the BIG differences in the alloys. 440C contains twice the carbon as 420HC, and several points more of chromium as well. Also has a little bit of Molybdenum, which is a carbide former (420HC has no Molybdenum). The percentage of carbon content, by itself, is the main determining factor in edge-holding (heat treat being the next most important). The chromium, when combining with the extra carbon, is going to create many more carbides in the steel (abrasion-resistance). So, the chemistry alone can account for both the greater edge-holding and the greater difficulty in sharpening, for 440C.

440C = 0.95 - 1.20% carbon, 16 - 18% chromium, 0.75% Molybdenum
420HC = 0.46 - 0.60% carbon, 13% chromium, 0% Molybdenum (none)

 

[Obsessed with Edges]

I've never seen nor heard of a carbon steel bladed Buck 300 series knife. 300Bucks would have to have the final word on that one, though.

According to Case, they have never changed the Tru-Sharp alloy composition. However, you might look at this thread, which shows that there has been some variation over the last 65 years.

http://www.bladeforums.com/forums/showthread.php/958884-Certs-for-CV-Steel-for-WR-Case

That link to the Case cert info is a great reference. Thanks for posting it. :thumbup:

I've sometimes wondered if some of Case's older carbon blades were 'different' than the established 'CV' blades of later years. I have a 1965-vintage folding hunter (6265 SAB) in carbon steel, and noticed it felt considerably 'softer' on the hones than the more modern CV blades I've sharpened. The upside though, is that older knife holds it's edge amazingly well. Seemed to have been a great combination of edge-holding and ease of sharpening.

 

[pinnah]

The difference in edge-holding can be attributed to the BIG differences in the alloys. 440C contains twice the carbon as 420HC, and several points more of chromium as well. Also has a little bit of Molybdenum, which is a carbide former (420HC has no Molybdenum). The carbon, by itself, is the main determining factor in edge-holding (heat treat being the next most important). The chromium, when combining with the extra carbon, is going to create many more carbides in the steel (abrasion-resistance). So, the chemistry alone can account for both the greater edge-holding and the greater difficulty in sharpening, for 440C.

440C = 0.95 - 1.20% carbon, 16 - 18% chromium, 0.75% Molybdenum
420HC = 0.46 - 0.60% carbon, 13% chromium, 0% Molybdenum (none)

David, as always, I'm deeply indebted to you for your help and patience. The advice you've shared in the past on sharpening has really transformed my experience my Bucks in particular.

I'm struggling with integrating what you've written above with my understanding. To clarify, I'm really wanting to better understand how Buck's 440C and 420HC differ in terms of the modality of their wear. I don't have a microscope and not sure I would know what to look for if I did and I know I'm asking a lot for people to speculate about how my knives are dulling sight unseen.

My understanding of dulling is as opposites of the 3 primary qualities of steel as Joe Talmadge describes it in his "Steel FAQ". Crudely summarizing and recasting as dulling....

Wear Resistance - the ability to withstand (uniform) abrasion. The dulling takes the form of (uniform) loss of material and with that, a rounding of the cutting edge.

Strength - The ability to take a load without permanently deforming. The dulling takes the form of longitudinal waves or lateral curls along the cutting edge.

Toughness - the ability to take an impact without chipping or cracking. The dulling takes the form of (non-uniform) cracks and chips along the cutting edge.


Given this, here is what I'm finding confusing about what you've written. My understanding from Talmadge's FAQ is that carbides primarily help with wear resistance, not strength. Strength (as I under his FAQ) is primarily correlated to hardness (which depends, in large measure on the heat treatment) and is generally inversely proportional to toughness. It is also my understanding that the primary way knives dull are from chipping (lack of toughness) and folding (lack of strength) and not abrasion (lack of carbides). This assertion came from the Qknife FAQ but it/may be somewhat supported by Talmadges claim (in the FAQ) that in wood carving, the primary stress on the blade is lateral stress at the edge causing it to deform.

All of this to ask, what is causing my 440C blade to dull when wood carving?

Is it finally abrading, even though it is much more abrasion resistant than 420HC due to the increased carbides?

Or it is micro-chipping, possibly because it was hardened to a high Rc and sharpened to too thin of a edge for sustained carving?

Or is it folding as is most common with carving but resisting my lame attempts at stropping because my strop kung-fu isn't strong enough?

Sorry for the long post and sorry to be such a nudge on this.

 

[Obsessed with Edges]

David, as always, I'm deeply indebted to you for your help and patience. The advice you've shared in the past on sharpening has really transformed my experience my Bucks in particular.

I'm struggling with integrating what you've written above with my understanding. To clarify, I'm really wanting to better understand how Buck's 440C and 420HC differ in terms of the modality of their wear. I don't have a microscope and not sure I would know what to look for if I did and I know I'm asking a lot for people to speculate about how my knives are dulling sight unseen.

My understanding of dulling is as opposites of the 3 primary qualities of steel as Joe Talmadge describes it in his "Steel FAQ". Crudely summarizing and recasting as dulling....

Wear Resistance - the ability to withstand (uniform) abrasion. The dulling takes the form of (uniform) loss of material and with that, a rounding of the cutting edge.

Strength - The ability to take a load without permanently deforming. The dulling takes the form of longitudinal waves or lateral curls along the cutting edge.

Toughness - the ability to take an impact without chipping or cracking. The dulling takes the form of (non-uniform) cracks and chips along the cutting edge.


Given this, here is what I'm finding confusing about what you've written. My understanding from Talmadge's FAQ is that carbides primarily help with wear resistance, not strength. Strength (as I under his FAQ) is primarily correlated to hardness (which depends, in large measure on the heat treatment) and is generally inversely proportional to toughness. It is also my understanding that the primary way knives dull are from chipping (lack of toughness) and folding (lack of strength) and not abrasion (lack of carbides). This assertion came from the Qknife FAQ but it/may be somewhat supported by Talmadges claim (in the FAQ) that in wood carving, the primary stress on the blade is lateral stress at the edge causing it to deform.

All of this to ask, what is causing my 440C blade to dull when wood carving?

Is it finally abrading, even though it is much more abrasion resistant than 420HC due to the increased carbides?

Or it is micro-chipping, possibly because it was hardened to a high Rc and sharpened to too thin of a edge for sustained carving?

Or is it folding as is most common with carving but resisting my lame attempts at stropping because my strop kung-fu isn't strong enough?

Sorry for the long post and sorry to be such a nudge on this.

The bolded part above, is exactly what I was getting at, about the carbides. In other words, carbides -> 'wear resistance' = 'abrasion resistance'. The resistance to abrasion (wear) is what makes 440C more difficult to sharpen (by 'abrasion') on the hones or strops. The rest of your quoted comments from Talmadge look right to me. I think he is right, in terms of the 'primary' ways in which blades dull (chipping or rolling). But, even with those 'primary' means of edge degradation, abrasion makes up a large part of the remainder. That's often what happens when cutting heavy cardboard, or fiberglass in particular, both of which are very abrasive. It's also why steel manufacturers have strived to improve wear-resistance (abrasion-resistance) by adding hard carbides (vanadium carbides, in particular, but also with chromium carbides and others).

The older 440C blades on Bucks were often known to break near the tips, as opposed to bending/deforming, when 'abused'. I'm thinking part of that might be due to larger grain size and/or heat-treat issues, which could also possibly suggest chipping issues with the steel. If so, you might be seeing that, in the 'dulling' of the 440C blades.

 

[knarfeng]

Mercy! As my pastor would say, "This thread has gone from Dan to Beersheba."
Started with where 420HC blades are made and here we are talking about 440C. Howsoever, as those are the defining Buck alloys, it's all good.

Hi pinnah,
My old Buck 110, which my folks gave me for a birthday present in the late 60's: 58.

I think David has given you a complete answer. In short, I don't think the 440C is cracking. It just takes more OOMPH to modify the edge because of the wear resistant carbides, which 440C has in abundance, but which are lacking in 420HC.

 

[pinnah]

Heh! My pastor says, "why do always fiddle with your knife during the sermon?"

Well, he says that to me anyway.

I really need a pocket microscope. I see that now.

Also really appreciate the help. My Lansky stone has more oomph than my strop!!

 

[davek14]

Mercy! As my pastor would say, "This thread has gone from Dan to Beersheba."
Started with where 420HC blades are made and here we are talking about 440C. Howsoever, as those are the defining Buck alloys, it's all good.

.

Yup, I've been reading along.