Chopper test & arms exercise

[awestib]

All awesome information bluntcut - way to go Sir!!

Keep the good work up - and keep us informed tooooo!

Andy

 

[BluntCut MetalWorks]

Thanks Andy!

I just finished testing a new batch(20150202) of 8 52100 knives (6 paring, 1 bread, 1 petty). 5 paring are fine. broken 3 - petty got saved into a smaller petty (6" instead of 8" blade). Yup, these test blades pave the way for my next chopper ht params with specs: 1/4" thick 52100 2.5" wide, 61rc, 0.022" edge thick, 10/13 dps.

Another test batch of 4 blades to gather ht params for ultra chopper with specs: 1/4" thick 52100 2.5" wide, 63rc, 0.020" edge thick, 8/12 dps. Wish me lucks.

I found a source for 1/4" x 2" CruV. So, instead of jump directly to D2, I might try to make two 16.5" OAL CruV choppers with same specs as above.

Prior to make a D2 chopper, I will make 3 small test D2 blades - to reconfirm my earlier results/blades, ensure high toughness at high rc is real not a waste of $.

All awesome information bluntcut - way to go Sir!!

Keep the good work up - and keep us informed tooooo!

Andy

Here is a macro view of my 6 paring (coupon tip - where I broke the coupon off to see inside).

 

[BluntCut MetalWorks]

Well, here is a - longer(23 minutes) than I intended - video. Tested baton & chop with small super quenched blades. Results look good for applying to my next large chopper: 52100 1/4thick x 2.5" wide 61+rc, 0.022" behind edge thick, 12 dps.

[video=youtube_share;2uvlNHcK1C8]http://youtu.be/2uvlNHcK1C8[/video]

Thanks for watching & comments.

 

[Chris "Anagarika"]

The test knives performance is shocking!

 

[BluntCut MetalWorks]

Thanks Chris! Hopefully when I use same ht params for the chopper and 0.022" behind edge thickness (which give 8x toughness by volume when thickness goes from 0.01 to 0.022) will be good enough for serious chopping & deal with scenario outlined above involved knots.

On my bench in the garage (underneath stuff) - I found 3 D2 and 1 elmax blades all wrapped in foil ready for ht. Three D2 0.05"/1.27mm thick 4"/10cm EDC test blades - all will have same ht. I will test 2- how these thin D2 blades fare with ~62rc, ~10dps ~0.01" edge thick specs, same tests - 'fail'/'FAIL'/'pass'? OK shall I even bother with ht and waste time on futile goal?

The test knives performance is shocking!

 

[chiral.grolim]

Thanks Chris! Hopefully when I use same ht params for the chopper and 0.022" behind edge thickness (which give 8x toughness by volume when thickness goes from 0.01 to 0.022) will be good enough for serious chopping & deal with scenario outlined above involved knots.

On my bench in the garage (underneath stuff) - I found 3 D2 and 1 elmax blades all wrapped in foil ready for ht. Three D2 0.05"/1.27mm thick 4"/10cm EDC test blades - all will have same ht. I will test 2- how these thin D2 blades fare with ~62rc, ~10dps ~0.01" edge thick specs, same tests - 'fail'/'FAIL'/'pass'? OK shall I even bother with ht and waste time on futile goal?

Well, at only 1.27mm it's pretty skinny but should make a good slicer. For heavier use (pounding) I think you'd want more stock-support material... 0.010 should withstand some force (it's not a chopper) but 10-dps may fold/chip at the apex if care is not taken. Good luck! :thumbup:

Here is a video abusing a Benchmade 15015 Skinner in D2 steel at 60-62 Rc - stock thickness is 0.14" and the edge is probably >0.020"... yeah, it's a fat little knife, but it shows that D2 isn't necessarily "fragile" as some might contend, though still not a rational choice for a chopper even if you CAN get it to work.

[video=youtube;yMIF_Xk-Bos]https://www.youtube.com/watch?v=yMIF_Xk-Bos[/video]

 

[BluntCut MetalWorks]

It took about a day to ht and prepared 4 knives for this test. I set out to break at least 1 knife. I am happy with the result, looking forward to make a 1/4" thick D2 chopper with ~62rc + 0.025" edge thick + 13dps.

Dry pine & white oak sticks strike down on a blade edge, where the blade spine is rested against cutting board. Hence termed reverse-chop.

All knives are 0.084" spine thick

Knife1: D2, 62rc, 9/10 dps (9* bevel, 10* micro bevel), 0.019" thick behind edge

Knife2: D2, 62rc, 8/10 dps, 0.015" edge thick

Knife3: D2, 63rc, 5/9 dps, 0.01" edge thick

Knife4: K110/D2, 64rc, 5/8 dps, 0.01" edge thick

Thanks for watching & comments.
[video=youtube_share;sz6OlNKRSWs]http://youtu.be/sz6OlNKRSWs[/video]

Microchipped


Cross section of a broken piece


edit: Finding out at what angle and thickness, my D2 blade able to whittle & feather pine wood.
I reprofiled the remain of the broken knife to almost zero grind. Sharpened to 3dps with behind edge thickness around 0.002". Slowly increase the bevel angle. Finally around 6-7dps & 0.004" thick, it whittled & feathered test (at least 50 cuts w/o edge deformation).



When & why I like chopper? That's me below...

 

[FortyTwoBlades]

Nifty chopper! I like the look of the mass distribution and the handle shape. To resist chipping out like that I'd probably leave the edge shoulder from the primary a little thicker. I think what's happening is it's thin enough behind the edge that the body of the blade is buckling under compressive side-load.

 

[chiral.grolim]

Thanks for watching & comments.
[video=youtube_share;sz6OlNKRSWs]http://youtu.be/sz6OlNKRSWs[/video]

Microchipped
View attachment 517845

Cross section of a broken piece
View attachment 517846

edit: Finding out at what angle and thickness, my D2 blade able to whittle & feather pine wood.
I reprofiled the remain of the broken knife to almost zero grind. Sharpened to 3dps with behind edge thickness around 0.002". Slowly increase the bevel angle. Finally around 6-7dps & 0.004" thick, it whittled & feathered test (at least 50 cuts w/o edge deformation).
View attachment 517935

Thank you for your continued efforts and public presentation of the results :thumbup::thumbup:

When & why I like chopper? That's me below...

The book? My wife and I watch your videos together and were guessing at your ethnic background! Thank you for linking it, will purchase and read :thumbup:

 

[BluntCut MetalWorks]

Thanks 42Blades! You are right, extra thickness would add cubic the radius-difference in toughness. Heck, it's more fun to find out the breaking limits. otoh, a chopper with 0.03" edge thick would be plenty(or too) thin for most consumer. Not good to have return-rate > 1%

I thinned this chopper out a little bit to pull its balance/sweet-spot about 1.5" back toward the handle. From a few more outings, this choppers excel with branches/trunks from 1 to 10" diameter. I tested back/forth between felling axe & chopper, draw prelim conclusion that 2.5-3" slightly curve (like samurai sword)contact length provides best penetration and low re-bounce. I will design a radical chopper with this attribute. This design will definitely call for a thicker behind the edge ~0.03-0.035" and 15dps. If failed, will make a new one similar to the one above except with aggressive ht specs but start with conservative edge geometry.

Nifty chopper! I like the look of the mass distribution and the handle shape. To resist chipping out like that I'd probably leave the edge shoulder from the primary a little thicker. I think what's happening is it's thin enough behind the edge that the body of the blade is buckling under compressive side-load.

 

[BluntCut MetalWorks]

Chiral! Thanks for watching & encouragement on my experiment. Hopefully you enjoy Catching Shrimp with Bare Hand (Mò Tôm) book. Michelle/author smiled happy & extend her thanks, when I showed her your post.

Thank you for your continued efforts and public presentation of the results :thumbup::thumbup:

The book? My wife and I watch your videos together and were guessing at your ethnic background! Thank you for linking it, will purchase and read :thumbup:

After examined and thought about the test blade breakage. See how the wood twisted grain steered the front of the blade more to the left than the other half. I don't think a thin blade in any steel with hardness > 61rc would survive this much sheering - quite a large gap at spine. For lower rc extra tough blade, its edge would mangle badly as well. What I get out of this scenario is don't pound a thin blade into twisted wood. In order to pound a blade into such wood, I would need a thicker blade. Where extra thickness: 1) wedge - limit penetration 2) arrest sheering 3) resist steering.


Well, I zero-regrinded the broken D2 into a 1.25" utility blade. after sharpened it has 0.005" behind edge thick ~7dps. Will see how this blade fare as my new main paper/leather/cardboard util.


** oh no, 1 more experiment before making new choppers **

Today, I cut 4 paring + a 24cm gyuto 52100 blanks. OK, the gyuto is for keep unless ht mishap.

I will go for ultra low hardening temperature - gyuto: 1440F; paring: 1435F, 1430F, 1425F, 1420F. FYI - 1450F considers bottom low austenite temperature for 52100.

Why? I seek super fine grain & 99+% lath martensite (tougher microstructure than plate martensite for steels with more than 0.9%C).

Target hardness gyuto: 64-65rc, paring: 62-64rc.

Your thoughts?

 

[Chris "Anagarika"]

Bluntcut,

Skimmed through thevideo, scary performance. :thumbup:
Yup. Thin blade shouldn't chop twisted wood.

 

[BluntCut MetalWorks]

Well, I am not as blind with my metal research as before. Yeah, I didn't make much progress without visual aid. So, I will take a step or two backward in order to go forth. Pic below shows my SQ52100 grain & carbide not as fine as it could/should be:grumpy: ... ok, hahaha time will tell whether I come up with even better ht.

SQ52100 at 1000x magnification - those large & tiny round shape objects are cementite and yellow scabs are martensite/matrix; some dark lines are shadow; some lines could be grain boundaries.

 

[BluntCut MetalWorks]

Wow, I sure can OT my own thread eh. Oh well... Voi'la much finer grain size

After SQ and hardness test (no temper). I broke off an attach coupon to a paring knife to see grain *as is* surface (no etch). 400x color negative, because of uneven surface the microscope only able to captured a thin strip in focus.

With eyeballs & a 15x Peak Loupe, I can't discern individual grain. I have 7 coupons need to polish & etch.

ASTM grain size quick table

5: 63.5um
10: 11.22um
14: 2.8um
15: 1.98um
16: 1.4um​

On average standard ht 52100 ASTM grain size is between 9 & 10.

 

[the possum]

Let's see here. Ya want good cutting ability, so the edge needs to be thin. Resist rolling and general deformation, so it needs to be hard. Chopping with it, so it needs high impact resistance. These requirements leave me scratching my head wondering why you're messing with D2 at all. Why not explore S5, S7, 5160, L6, 3V, etc.? I'd love to see what S5 would do around 61 Rc with a thin edge. On paper it should be one of the toughest steels there is at high hardness.

 

[BluntCut MetalWorks]

Your reason make a lot of sense. But perhaps humor my possibly irrational reasoning & fun ...

D2 has super low impact toughness especially at 63+rc. Along with large carbides, one should expect to get an over-baked cookie for a blade. I enjoy taking on challenges down right to derpy level. My goal is to ht a D2 63rc blade which capable of performing tough tasks as 5160/80crv2 blade - both at same edge geometry. Aahh but what's about steel composition & metallurgist wisdom & empirical data already predict my goal is doom/dumb.... I've this idea and yet more ideas with ht D2, which is more fun to do than choosing known safe tough steels. Cool thing is any advances I made with D2, could/would enhance/applicable to other steels.

Wish me lucks - a lot of lucks :thumbup:

Let's see here. Ya want good cutting ability, so the edge needs to be thin. Resist rolling and general deformation, so it needs to be hard. Chopping with it, so it needs high impact resistance. These requirements leave me scratching my head wondering why you're messing with D2 at all. Why not explore S5, S7, 5160, L6, 3V, etc.? I'd love to see what S5 would do around 61 Rc with a thin edge. On paper it should be one of the toughest steels there is at high hardness.