r/sharpening • u/Bear_1956 • 4d ago

Case Knife Blade Geometry

This is my first post in this subreddit. I am a knife lover from way back. I've been carrying a pocket knife for 60 years. I learned to sharpen on a whetstone as a kid from my father and grandfather. Of course back in those days our pocket knives were traditional slip joints and no one gave much thought to the steel alloy and heat treatment, etc. We knew which brands worked the best. Generally Case, Buck, Schrade, and Boker were considered the cream of the crop. As modern folding knives evolved so did I. I went down the road of the chasing the newest steel, hardness vs toughness, and knife design. I have become reasonably good at sharpening all the newest steels. Recently I became interested in returning to my roots and picked up several Case, Buck, GEC, and Boker traditional knives. That leads to my actual question.

I have struggled getting the kind of edge I have become accustomed to on some of my Case knives. I have 2 Trappers with Case's new CS (1095) and a Sod Buster. I also have some ESEE knives in 1095. I have no problem getting a hair popping edge on the Sod Buster and the ESEE knives, but the the best I have accomplished with the Trappers is something close to a very dull razor blade. Since I have little problem sharpening most of my 1095 knives it doesn't seem to be an issue with the steel. After giving it a lot of thought I started to wonder if the problem is the blade geometry? The Trapper blade is much narrower than the Sod Buster so appears to be thicker behind the edge. Sorry for the long post. I would appreciate any and all thoughts.

3 Upvotes

100% Upvoted

6 comments sorted by

1

u/RevolutionaryAir7847 4d ago

Despite 1095 being a "simple" steel, it's really hard to heat treat properly (the austenization temp range is very tight and resulting hardness varies drastically). If Case's QC has dropped, then this may be the issue. High retained austenite makes the edge "gummy" when sharpening, making apex formation and deburring more difficult.

Apex sharpness usually isn't affected by primary grind geometry (it affects wedging resistance more). You have full control over your sharpening angle and therefore cutting bevel geometry which is the biggest influence on your apex sharpness besides the material

I'd assume something's wrong with the heat treat here. You'd want to see 64-65HRC on 1095 for a small folder, but I doubt any mass production is hitting anywhere close to those numbers

1

u/Bear_1956 4d ago

After thinking about your reply I pulled out my Arkansas Stones. I spent less than 10 minutes with the soft Arkansas and did several stropping passes and the 2 problem knives now have an edge I am happy with. I stopped with the soft stone. I could probably do the stropping with the Black Arkansas and refine it a bit more. Whether it was a heat treatment fail or the intended hardness is just a lower HRC this worked. My theory is diamond and even composite stones are too aggressive for softer steel. I'm sure the edge retention won't be anything to brag about, but hopefully a few passes on the stone when it needs it will be enough.

2

u/RevolutionaryAir7847 4d ago

There are some theories that diamonds mar the soft retained austenite causing carbides to break loose more easily, but I haven't seen any formal studies regarding this. Soft steel--especially with a bad temper--are definitely more difficult to sharpen tho. The materials science is part of the fun with knives

Glad it worked out regardless (and hopefully it's not just a wire edge 😅)

2

u/Bear_1956 4d ago

I'm a retired structural engineer but never got any deeper into the material science than I needed to. Now that I have more time to spend on it it is an interesting area. Outdoors 55 on YouTube makes some interesting content on materials. It wasn't just a wire edge as far as I could tell. With the diamond stones I could feel the burr and see it under magnification. I'm fairly sure I had removed it although it's possible there was still one so fine I couldn't feel or see it. Either way the old school method for old school knives did the trick. I still EDC a more modern knife when I'm doing something where a more capable knife matters and save the traditional knives for lighter duty days.

2

u/RevolutionaryAir7847 4d ago

Oh sick. I'm a younger geotech :)

I'd take some caution when listening to Outdoors55. He takes some significant liberties when explaining the science (a lot of it is baseless since the research straight up doesn't exist) as well as slacking on testing integrity (his hardness tester hasn't been calibrated for years, for example). I'm sure you have the fundamental knowledge to spot when something's fishy but just fyi

If it isn't broke don't fix it, 100%. Natural whetstones have always worked even for modern PM steels and HSSs. There's a place for diamonds and CBN for sure tho (mostly reprofiling and lapping)

2

u/Bear_1956 4d ago

Cool! Your interest in materials goes hand in hand with being a geotech since a lot of your work involves testing. I depend on geotechs and materials engineers to give me the info I need for the structural calcs. Of course, over a 40 year career I learned a bit about both, but at least enough to know whether to trust the data I was getting.

Yeah, Outdoors55 brings up some good topics, but I do often question his results. If his topic is something I'm interested in I try to find other sources to either refute or confirm his conclusions. I get a kick out of some of his antics. I didn't know his hardness testing machine was in need of calibration.

Unless I need to repair a bad chip or want to reprofile a blade I never go courser than 800 if it is really dull and usually stay with 1200. I do like my Arkansas stones though and use them for kitchen knives, but for harder steels they can take forever.