BCMW's ht chopping impact tests

Luong,

Watched the 5 mins test. Nice thin edge & curls, and it seems it cut smoothly after the chopping:confused: ??

Side note:
I'm keeping the SU as the rounded spine is very nice in the U part of SU.
Besides it rings nicely when in use ;)
 
I agree, convex/apple-seed blade grind would takes less work and stronger too. I am looking for limits on what an insufficient strength edge (not enough steel volume) against very large impact/impulse forces. A heavy chopper can put a large impact load in small area and with ample momentum where steering can lead catastrophic damages.

When my new order of steels arrive. I will make most 0.160-0.175" thick 7" blade (12" OAL) test blades - I can zero grind these to magnify failure situations.
dadamsjr said:
What if you tired doing a convex grind instead of the flat?
Click to expand...

Not too bad eh :cool: I will test this chopper(same edge area) - zero grind (6 dps), 12 dps (shoulder 0.006" thick), 15dps micro (shoulder 0.002" thick).... Goodbye chopper!
Chris "Anagarika";15849719 said:
Luong,

Watched the 5 mins test. Nice thin edge & curls, and it seems it cut smoothly after the chopping:confused: ??
Click to expand...

Yeah, I remember how nice it rings. Don't recall hearing any of my recent blades ring/sing/dance :p
Side note:
I'm keeping the SU as the rounded spine is very nice in the U part of SU.
Besides it rings nicely when in use ;)
Click to expand...
 
full zero grinded (6dps) the chopper and a very small 15dps micro bevel - very hard to see with naked eyes.

Edge after chopped 1.5"sq Cumaru wood(15th down from this list - https://en.wikipedia.org/wiki/Janka_hardness_test)

* max damage thickness extended to 0.025" after chopped 1.5"sq Lignum Vitae Argentine.

1VsX63i.jpg


Edit0: Chop-exits exert quite a bit of lateral forces on the edge

Edit1: 52100 63-64rc jb, 0.02" BET, 13dps. Lignum Vitae chopping tests: passed
W2 65.5rc jb, 0.025" BET, 15dps. Lignum Vitae chopping tests: passed
 
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52100 63-64rc jb, 0.015" BET, 13dps. Lignum Vitae chopping tests: passed. African Blackwood - passed with a few micro deformations (looking through 22x loupe).

After more 16d (0.162" dia) nail chopping; granite splitting; African Blackwood afraid-to-chops; digging; bending; etc... I am looking at ht vs usage WAG as follow

Non-impacts with low lateral/torsion (kitchen, etc): W2 68rc, 52100 67rc, 1095 67rc.

Non-impacts with heavy press cuts and some lateral/torsion (EDC/EDU): W2 66rc, 52100 65rc, 1095 65rc.

Low psi impacts (small work knives): W2 66rc, 52100 64rc, 1095 63rc. Damage mode = blunt/dent to 0.5mm, chip up to 3mm(on high psi impact), pry beyond yield = break.

Med to high psi impacts: W2 65rc, 52100 63rc, 1095 62rc. Damage mode = blunt/dent up to 1mm, chip 1-2mm, pry beyond yield = break (very narrow plastic region).

High psi sheering impacts: W2 63rc, 52100 62rc, 1095 61rc. Damage mode = deformation (rolled & dent), pry beyond yield = set (stay bend, wide plastic region).

* WAQ - can CruforgeV beats 3V in every categories but corrosion resistant?

* btw - Called NJSteelBaron - W2 0.187" and possibly 0.156" avail in 8-10 weeks. Looking forward to getting W2 at these thickness.
 
Interesting....so how would you rank those three steels in terms of performance? W2, 52100, and CruforgeV?

You think a heavy chopper can have a ~62 / 63 rockwell hardness and be fine? How much better is the edge retention on such a hard blade vs. the industry standard 57 - 59 rockwell for heavy choppers? Is it that much better to be worth giving up the much greater toughness of a typical high 50's rockwell chopper?
 
I would guess: Perf rank my Ht for chopping knives/choppers - W2, 52100 (96-98% W2), Cfv (90% W2). Higher carbides volume & large dia = higher fracture chances.

Strength & toughness are key factors for chopper edge retention. If chopping force is below steel yield point in edge, strength is the key. Toughness help minimize edge damage - trying to preserve the edge w/i working condition

Let's take a scenario - task = 100x chops 1" deep into 2x4 oak. Expertly optimized (as thin as it can supports, hence thinner = edge failure) chopper A weight 24oz, 0.03" behind edge thick, 20dps, swing at 3ft/s. (maybe exaggerate to make a point) Chopper B is stronger A but just as tough as A(at mininum because can't optimize geometry any thinner), so B only weight 18oz, 0.015" BET, 15dps, swing at 3ft/s. Both A & B meet 1" deep chop requirement.

From work efficiency view point - Chopper B is 25% more efficient(took 25% less work) than A.

For intended tasks - B shouldn't/can't be 'giving up' much. Otherwise, it would be - rob Peter to pay Paul. Word 'much' because a stronger B could/probably be harder to sharpen than A.

The Last Confederate said:
Interesting....so how would you rank those three steels in terms of performance? W2, 52100, and CruforgeV?

You think a heavy chopper can have a ~62 / 63 rockwell hardness and be fine? How much better is the edge retention on such a hard blade vs. the industry standard 57 - 59 rockwell for heavy choppers? Is it that much better to be worth giving up the much greater toughness of a typical high 50's rockwell chopper?
Click to expand...
 
52100 1/4" thick jest bolo 63-64rc, 0.015" BET, 11dps <= way too thin now, so edge steering caused a large ripple. I was swinging really hard at 45 degrees chopping angle right into a pin knot.

apex shows micro ripples as well (those are not chips).

Plenty of toughness - I think.

QSXxMOO.jpg


edit: I was looking to see 63.5rc 52100 encounter impacts passed yield into plastic region. Ripple = plastic/bent. Will gradually making a 15dps micro bigger until volume strength is enough to avoid (my swing strength) steering in choppings.
 
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Guys :thumbup:, I appreciate your enthusiasm about BCMW debut!

After examined the rippled edge above, plus newly rippled edges. These ripples without rolled nor chipped, indicate deformations were due to insufficient lateral strength, where compression strength is fine even at 11dps. Micro bevel + wedge-height&base tuning is such highly variable depend on impacts (user strength, material being chop, force vectors, etc..). Maybe more pragmatic, I will use a conservative geometry - 15dps, 0.015" BET, which has 2.54 times volume strength of 11dps (and same wedge height).

Relative volume strength - normalized at 22 and 30 degrees inclusive.
bB9B4xk.jpg
 
bluntcut said:
Light chopping tests
W2 1/8" thick, 3.5" blade, 67.5rc
0.014" behind edge thick, 13.5dps

Thanks for watching & comment.

==Luong

[video]https://youtu.be/37UyGE2rM78[/video]
Click to expand...

I cannot view this video. Strange.

Anyway, assuming differential temper have you tried bend tests to see what happens when you bend a hard edge with a soft spine? It would be interesting to see how much flex the edge can take given a soft tough spine.

Also, you may remember some tests I did using large cement nails. Others have used regular nails with little damage but the large cement nails I think really test the toughness of a steel as they create a large c-notch and continued hammering into the nail can propagate a crack like it did in the 1095 crovan in less than 2 minutes.
 
Cobalt said:
I cannot view this video. Strange.

Anyway, assuming differential temper have you tried bend tests to see what happens when you bend a hard edge with a soft spine? It would be interesting to see how much flex the edge can take given a soft tough spine.

Also, you may remember some tests I did using large cement nails. Others have used regular nails with little damage but the large cement nails I think really test the toughness of a steel as they create a large c-notch and continued hammering into the nail can propagate a crack like it did in the 1095 crovan in less than 2 minutes.
Click to expand...

Link to test?
 
Sorry for the delay - I am traveling w/o a laptop. Finally, online but will be spotty. Please activate your messaging option or contact my gmail

flexdog2008 <= text in white color :)

==Luong
dadamsjr said:
Hey I tried sending you a message can you message me
Click to expand...
 
Steel has elastic stretch & compress limit. Thin(e.g. edge; fillet blade;etc) cross section will flex more because small distance off-center, thus less stretch & compress. Most of the time the thicker spine will exceed elastic, then plastic before the edge. So softening spine to give it a wider elastic range. Of course, stretching is directly tied to bending radius. Hold one end at the xy origin, bend the other end until it reaches y-axis (zero for y). X distance tells you how flexible for different material with same geometry.

Plastic/dutility cease to function at certain level of pile up (compressed / squeezed-out), so pounding/compressing some steel - once compressed wall take hold, force will initiate a crack and propagate along the sheer canyon (in the case of whacking on a hardened nail - basically compacting the steel).



Cobalt said:
...
Anyway, assuming differential temper have you tried bend tests to see what happens when you bend a hard edge with a soft spine? It would be interesting to see how much flex the edge can take given a soft tough spine.

Also, you may remember some tests I did using large cement nails. Others have used regular nails with little damage but the large cement nails I think really test the toughness of a steel as they create a large c-notch and continued hammering into the nail can propagate a crack like it did in the 1095 crovan in less than 2 minutes.
Click to expand...
 
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