BCMW's ht chopping impact tests

BluntCut MetalWorks

BluntCut MetalWorks

Knifemaker / Craftsman / Service Provider
Joined
Apr 28, 2012
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I am on my 3rd years trying to perfect my ht. Recently done a few round of tests on 3-5" blade knives. Chopping impact test is next. Yesterday, I ordered some thick steels from Aldo/NJsteelbaron. A BF member got me into using Jest Bolo pattern, otherwise I would happily make another one using my previous pattern.

Jest bolo #1 - 0.312" W2. If it went well, make Jest bolo #2 - 0.156" 52100

http://i.imgur.com/Ogsjs9s.jpg
Ogsjs9s.jpg


Intended usages/tests/goals:
* Chop through 2x4 Douglas Fir in 6 chops or less.
* Fastest chops and mis-chops at seasoned oak board.
* Hardest swings (I can muster) at pin-knotted seasoned pine; dried olivewood (~2700 lb force in janka); Cumaru 1.5x1.5 square (3540 janka).

My plan is evolving, thanks for any inputs or comments.
 
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My goal for this chopper final working hardness is between 63 and 66rc. So strength & toughness must be quite high in order to sustain hard chopping impacts.

For comparison: hardness of Japanese high end kitchen knives are usually between 62 and 64rc.
 
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Love that blade design! I'll be looking forward to your test results and maybe you'll have one to sell at some point :)
 
I love the design also. Looks like you are pushing the limits.:thumbup:
Best of luck with the heat treat. I would like to help you test,
 
Thanks, dogrunner! It's quite easy to perpetually stuck in experimental mode. Umm from recent news, I wonder if I could incorporate gravitation wave into my ht - oh wait, done:p

dogrunner said:
Love that blade design! I'll be looking forward to your test results and maybe you'll have one to sell at some point :)
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Thanks.

My previous W2 at 62rc with thinner edge geometry, so a 63rc at thicker edge geometry would be a par.
My aim looks like this:
* 63rc - ho hum
* 64rc - good
* 65rc - on target
* 66rc - delighted

Push cutting/chopping edge retention is excellent when hrc > 63. Abrasion wear improvement is minute/trivial.

LG&M said:
I love the design also. Looks like you are pushing the limits.:thumbup:
Best of luck with the heat treat. I would like to help you test,
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Just noted the specs on the 52100 you are planning. I like that steel and am looking forward to what spyderco does with it in the mili sprint. And I'm very interested in the performance you will get with your ht and that stock thickness. I like my choppers fast and light (relatively speaking). Heavy wears me out and my elbow tendinitis flares up. The .156 has my attention!
 
This W2 chopper isn't that heavy, planned weight is between 18 to 20 oz.

For 0.156" thick 52100, its projected weight probably be right around 12-15 oz. From tested 52100 bushcraft knives, ~63rc is probably an upper working limit hardness for chopper with my 52100 ht.

dogrunner said:
Just noted the specs on the 52100 you are planning. I like that steel and am looking forward to what spyderco does with it in the mili sprint. And I'm very interested in the performance you will get with your ht and that stock thickness. I like my choppers fast and light (relatively speaking). Heavy wears me out and my elbow tendinitis flares up. The .156 has my attention!
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Unfortunately I don't have use to help testing, but very much interested in the test results, especially 52100!
Your 52100 has always been special even in experimental mode:thumbup:
 
Thanks, Chris!

I get to know/understand quite a bit on how to ht 52100 for high performance. Lately, I get exceptional result with W2 steel from NJSteelBaron. I think, composition of this W2 is outstanding and seem very clean ingot as well. Well, double the fun for me - I guess :)
Chris "Anagarika";15751512 said:
Unfortunately I don't have use to help testing, but very much interested in the test results, especially 52100!
Your 52100 has always been special even in experimental mode:thumbup:
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After did more handling of my previous chopper + took input from KWB. Added some flare to handle tail to keep this chopper from wanting to fly away. Tang will be skeletonize. Replaced finger guard with forward choke - to save some weight. Open heel for ease of sharpening and allow close up heel cuts.

ShkBkAA.jpg
 
I've 2 blanks of 1/4" thick 52100 chopper sitting around. Not sure, if/when I would make choppers using the original pattern, so might as well repurpose 1 for a jest bolo.
9pTyGIC.jpg
 
Cut & paste part of my post from else where:

We can look at my quest in a perspective of apex radius (for simplicity just consider it a flat top on a slanted wall/bevel). Yup, what is a minimum strength required to withstand a given impact. So the apex radius would be inverse proportional (some function value) to steel tensile strength.

This jest bolo is a fairly heavy and low velocity chopper. But would be nice if it can chops through dry blackberries/etc.. which requires either high velocity or very sharp (thin apex radius). Well, it not easy to swing really fast (beside dangerous), otoh with very high hardness could support thin enough apex radius to perform this task at low velocity.

More than likely that I will test chopping impact with edge thickness floor around 0.012" and edge finished around 5K shapton pro.
 
Here is the TIP (test in progress) of 52100 jest bolo. 13.3 oz (est with handle around 17oz); 0.02" behind edge thickness, 12 dps (no micro bevel). End up with edge geometry thinner than planned because I had to re-harden this blade then grind-off the decarb afterward.

There is a little rippled on the edge (on the ramp of the recurve) from light chopping seasoned knotty olive wood. No problem with hard chops into seasoned oak log & board.

c0LCHDv.jpg



bluntcut said:
I've 2 blanks of 1/4" thick 52100 chopper sitting around. Not sure, if/when I would make choppers using the original pattern, so might as well repurpose 1 for a jest bolo.
9pTyGIC.jpg
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No micro at 12-dps and only a bit of rippling evident...

Do you think you might need to add that micro-bevel or thicken the edge slightly to 0.025" against the risk of catching a bad hit a propagating a fracture up the primary?

How did the douglas fir board-chop go? <6 hits?
 
Edge geometry got measured after the test, oopsy too thin.

I mis-chopped (bad angle and deflected) the dried oak log (firewood chunk) around 5 or 6 times - no problem. Sure, I was a bit worry early on but onset to unfounded confidence lead me to hack dried olive wood. The ripple went around 0.015" up the bevel.

Not sure what to do yet:
1. Keep 0.02" BET, 15dps/20dps micro.
2. 0.025" BET, 15dps/20dps micro. High probability of a hard working geometry.
3. Thin to 0.01" BET, 15dps/20dps micro. Looking for gross damages against woods with janka > 2500.

I don't have a good setup for low-strike-count chopping dried 2x4 douglas fir. It tooks around 12 chops turned a 12" long 2x4 into two pieces.
JvhmRlH.jpg



chiral.grolim said:
No micro at 12-dps and only a bit of rippling evident...

Do you think you might need to add that micro-bevel or thicken the edge slightly to 0.025" against the risk of catching a bad hit a propagating a fracture up the primary?

How did the douglas fir board-chop go? <6 hits?
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This 52100 jest bolo got new handle - African Mahogany coated with a fresh coat of oil. Current weight = 16.8 oz.

vzZ9HGN.jpg
 
Thanks, Colin.

The adapted handle profile feel very secure in hand and comfortable too. So, I will use this handle profile for W2 jest bolo. LOL - first time drill holes for corby bolt, hence got the first time look.

My oven is only 18" deep, so usable/practical max blade length for ht is around 16.5". I can push for 17.25" if I stick the blade tang first into oven, to avoid over heat the tip. Eventually, I probably will buy a longer(27") oven.

Camber said:
Man Bluntcut, I love that design. How big of a blade can you make again?
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