BCMW's ht chopping impact tests

[dogrunner]

Theoretically, hummingbirds and bumble bees can't fly But they obviously do, despite the calculations of physicists and engineers.
I enjoy the discussion / debate about metallurgy, but am very interested to see the empirical results of experimentation with materials, design, and HT. So my thanks to Bluntcut and all the testers out there. It is sometimes confusing and never a linear path to understanding, but without the experimentation we never break new ground.

Still watching with interest and thanks for the reports and critiques!

 

[BluntCut MetalWorks]

:thumbup:

A 21.22 minutes video is being upload to youtube. My tests weren't harsh enough, thus failed to establish(find out) a 3.5" W2 67.5rc test blade's limits.

Theoretically, hummingbirds and bumble bees can't fly But they obviously do, despite the calculations of physicists and engineers.
I enjoy the discussion / debate about metallurgy, but am very interested to see the empirical results of experimentation with materials, design, and HT. So my thanks to Bluntcut and all the testers out there. It is sometimes confusing and never a linear path to understanding, but without the experimentation we never break new ground.

Still watching with interest and thanks for the reports and critiques!

 

[BluntCut MetalWorks]

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]

 

[noseoil]

Luong, excellent video! Nice to see the results from a very hard blade. Is it a "super-quench" type of heat treatment, or something different on this one? It must be pushing the limits of hardness for that steel....

 

[BluntCut MetalWorks]

Thanks, Tim. How are your D2 blades going?

Super-Quench(SQ) is simply a super-fast cooling/quenching part of ht. A faster cooling = less elements movement while cooling from austenite temperature to martensite transforming(phase change) temperature. e.g. quenching/cooling a piece of steel 0.1" thick 1"x2" WxL from 1500F to around 400F takes: slow oil ~20 seconds; medium (viscosity) ~11s; 140F canola oil ~9s; Parks 50 ~7s; water ~6-7s; brine ~5s; super-quench (brine+dawn hand dish-washing soap+surfactant) ~3s. SQ shock-wave is neat, especially on a long and wide blade.

Today both W2 blades end up at tempered 67.5rc. Tomorrow, I will harden another W2 blade (darn, I only have 2 blades left) aiming for 68-68.5rc and test it at that hardness. One blade 67.5rc W2 will face in stages copper-wire->16d nail->cinder-block->rock tomorrow. I probably will torch-soften a spot on the spine for receiving hammer blows. Limits should shown themselves from examine edge or blade damages.

52100 is no slouch. For now, it's only trailing W2 by 1rc.

Luong, excellent video! Nice to see the results from a very hard blade. Is it a "super-quench" type of heat treatment, or something different on this one? It must be
pushing the limits of hardness for that steel....

 

[dadamsjr]

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]

Thank you for your time and efforts in doing these tests. It's appreciated!

 

[Chris "Anagarika"]

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]

Luong,

Thank you for sharing the progress, it's getting more amazing!

 

[BluntCut MetalWorks]

:thumbup:

Thank you for your time and efforts in doing these tests. It's appreciated!

Luong,

Thank you for sharing the progress, it's getting more amazing!

Let's look at that W2 edge after light chopping tests. Aha, there they are - micro chips.

In spite of thin edge geometry, there is no large/macro damage. A projection - 67.5rc edge at 15dps may sustains light chopping tests w/o micro-chipped.

 

[chiral.grolim]

In spite of thin edge geometry, there is no large/macro damage. A projection - 67.5rc edge at 15dps may sustains light chopping tests w/o micro-chipped.

Luong,
The damage sustained should not require raising the entire bevel to 15 DPS and 0.02" to avoid damage, why not just add a tiny microbevel at 15 or 20-dps?
The microbevel need only be 0.001" wide, it would be trivial to add and have no measurable impact on cutting efficiency but should provide the stability required to prevent the damage presented. If it does not, a slightly thicker microbevel and so on.

 

[BluntCut MetalWorks]

Excellent; agree :thumbup:

Soon this blade will endures hard tests where expected damages will be substantial even when the edge bevel increased to 15dps and 0.015-0.02" BET.

New test sequence would be: *chop-into = at it but not sever/split*
1. baton & chop-into copper wire
2. baton & chop-into small sand stone/rock
3. baton & chop-into cinder block (if I can find any around my yard)
4. chop-into & baton small granite rock
5. tap (using a metal hammer) & chop-into 16d nail

Place your bet here ...

Luong,
The damage sustained should not require raising the entire bevel to 15 DPS and 0.02" to avoid damage, why not just add a tiny microbevel at 15 or 20-dps?
The microbevel need only be 0.001" wide, it would be trivial to add and have no measurable impact on cutting efficiency but should provide the stability required to prevent the damage presented. If it does not, a slightly thicker microbevel and so on.

 

[RX-79G]

Oh, are you Luong of the super quench from hypefreeblades? Your English has improved radically.

 

[BluntCut MetalWorks]

Yes, I am on HF as Luong La.

Oh, are you Luong of the super quench from hypefreeblades? Your English has improved radically.

 

[bodog]

Excellent; agree :thumbup:

Soon this blade will endures hard tests where expected damages will be substantial even when the edge bevel increased to 15dps and 0.015-0.02" BET.

New test sequence would be: *chop-into = at it but not sever/split*
1. baton & chop-into copper wire
2. baton & chop-into small sand stone/rock
3. baton & chop-into cinder block (if I can find any around my yard)
4. chop-into & baton small granite rock
5. tap (using a metal hammer) & chop-into 16d nail

Place your bet here ...

Knowing what I already know I would not bet against your knives performing as well as the steel they're made of can perform.

 

[chiral.grolim]

Excellent; agree :thumbup:

Soon this blade will endures hard tests where expected damages will be substantial even when the edge bevel increased to 15dps and 0.015-0.02" BET.

New test sequence would be: *chop-into = at it but not sever/split*
1. baton & chop-into copper wire
2. baton & chop-into small sand stone/rock
3. baton & chop-into cinder block (if I can find any around my yard)
4. chop-into & baton small granite rock
5. tap (using a metal hammer) & chop-into 16d nail

Place your bet here ...

The copper wire and 16d nail should be a snap - much softer metal (copper is ~163 Knoop, this blade is ~900) - but the others may not be not so good These >65 Rc blades avoid bending/folding (strain) and thereby avoid presenting a surface to receive significant lateral stress that leads to failure, but impact toughness must come into play eventually, most likely when thin 900 knoop edge meets fat 900 knoop granite (well, more likely 750 knoop, but it's pretty close and may be much thicker)

 

[knife chop]

This is crazy. have you tried bending the knife to see how tough they are at that hardness?

 

[chiral.grolim]

This is crazy. have you tried bending the knife to see how tough they are at that hardness?

... I don't think it would bend very far ... stress/strain and all. But wouldn't that be more a measure of strength? Or are you just wondering about how "brittle" (fractures almost immediately upon permanent deformity)?

 

[BluntCut MetalWorks]

I need to create failures - find limits when a blade is most vulnerable. Yes, when it's at as-quenched state.
Today, a new blade got hardened at 68rc. Grinded clean & put on a quick edge. Ah, decided to epoxied this short stick tang test blade to long stick of cherry wood for handle.

* warning - a painful 17 minutes video *

W2 1/8" thick, 68rc as-quenched/untempered
0.020"/0.51mm behind edge thick
edge bevel angle 15 degrees per side (30 degrees inclusive)

Thanks for watching & comment.

==Luong
[video]https://youtu.be/xnjxnkn02Y4[/video]

Close up look at the broken test blade

This could be a blade with bad ht preps steps (1 among 6 blades) - the crack in the tang maybe the one. I will test another as-quenched (will check for post-harden cracks next time).

 

[BluntCut MetalWorks]

You are right - tap/press through copper wire & nail should be easy. They were. However chopping them is very troublesome because of wedge/bind/rebounce with lateral forces involved. Unfortunately, my handle broke too soon.

Chopping at rocks actually easy on the edge (I've done that quite a few times before) because over all psi is lower than a small radius objects like nail. OK, chopping a corner of a granite would be worse among these tests inflict high edge damage however won't cause a blade to split

In the video - tapped through nails didn't do much damage to this untempered edge. Most of major damages were caused by the harder rock.

The copper wire and 16d nail should be a snap - much softer metal (copper is ~163 Knoop, this blade is ~900) - but the others may not be not so good These >65 Rc blades avoid bending/folding (strain) and thereby avoid presenting a surface to receive significant lateral stress that leads to failure, but impact toughness must come into play eventually, most likely when thin 900 knoop edge meets fat 900 knoop granite (well, more likely 750 knoop, but it's pretty close and may be much thicker)

 

[BluntCut MetalWorks]

I didn't have a chance to go through with tests for toughness via chopping. Incidental toughness test (actually lacked toughness) stemmed from hammer strikes. This type of fracture is well-known/study. Edge incrementally cut through a nail with tapping is mostly a test of strength with small load of force. Impulse force from a chop would test the steel ability to withstand certain load, fracture occurs when force exceeded the load capacity.

Add to what Chiral said about bending... Larger radius in Young Modulus (larger bending section) would certain help distribute the force over a larger area but bending doesn't help much in high impulse (fast stop) strikes (chop nail) because the force vector is narrow with high energy propagating quickly into the blade (toward the spine). Another example of extreme would be chop into a case-hardened dry wall screw - edge would chip and or dent mostly in the shape of the screw.

This video is valuable to me, it re-confirmed a few things I already know and learned something new about as-quenched/untempered steel matrix.

This is crazy. have you tried bending the knife to see how tough they are at that hardness?

 

[BluntCut MetalWorks]

Whew! I glad you didn't bet, otherwise I might have lost a case of Lobotomy Boch

Knowing what I already know I would not bet against your knives performing as well as the steel they're made of can perform.