S125V 66rc Chopper

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BluntCut MetalWorks

BluntCut MetalWorks

Knifemaker / Craftsman / Service Provider
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Apr 28, 2012
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I will make a S125V (3.3%Carbon) chopper with specs: 2.25"W x 0.275" Thick, 15" OAL, 64-65rc, 18dps, ~0.025" behind edge thickness

After testing, its dimension will meets BladeSports specs.

It might be the first chopper in the world in s125V steel. it would be interesting/educational to evaluate proof of HT 6.0 concept.

Test via my maximum chop speed at tasks: 2x4, hardwoods and very high janka woods, dried pork rib bone, [ your susggestions ? ]. Performance = 'A' no visible damage, 'B' no chip/damage larger than 0.5mm tall, 'C' 1mm, 'F' otherwise.

I placed an order for a bar of s125V from nsm nsm , sufficient length for making 2 choppers.

Thoughts?
 
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Well well well, I finally picked 'best' chopper steel according to Knifesteelnerds/Larrin - while I am hanging upside down 🤣

M398-toughness-chart.jpg
 
tinfoil hat timmy said:
looks like you have your work cut out for you dont you? 😀🙃
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Yup!
In order get an A or B grade from the testing criteria and edge geometry above, steel must has high strength(64+rc as useful indicator) and need a guesstimate 10+ ft-lbs in toughness. This objective seems unreasonable/unattainable/delusional, right? 🤔
 
bluntcut said:
Yup!
In order get an A or B grade from the testing criteria and edge geometry above, steel must has high strength(64+rc as useful indicator) and need a guesstimate 10+ ft-lbs in toughness. This objective seems unreasonable/unattainable/delusional, right? 🤔
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based on the chart you've provided it does seem like no one has accomplished that.

yet!
😀👍
 
s125v is a very brittle steel.... even with a great heat treatment, but I'm curious to see your results...

If I was trying to make a high hardness stainless chopper, I'd be looking at aeb-l, or magnacut for higher edge retention

BluntCut MetalWorks BluntCut MetalWorks please share results - I'm curious if you can get ANY geometry on s125v which withstands chopping abuse
 
Let's use deduction to see whether my ht conceptual test objective is reasonable or not. Using the chart for control ht, 62.5rc S90V ~ 4 ft-lbs (compare to 3 for s125v). Rough linear projection: 3 to 2 ft-lbs at 65rc. thus at 65rc S90V is 50% tougher than s125v.

Jump to BCMW HT
At 65rc 18dps, if s90v get an A or B grade then s125v is within 50% of accomplish the objective, instead of 500+% if using control ht. Otoh grade F(ailed) S90V (HT5TFx and next HT6) would/could mean ... hello hello frontal cortex, lest expand neural sharpening actions (potential) to include analytic and abstraction, yup grow another tree of life :p

Edit: here is 65rc S90V 20dps test result - https://www.bladeforums.com/threads/s90v-chopper.1790760/post-20556077. I need to test it at 18dps
 
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dirc said:
s125v is a very brittle steel.... even with a great heat treatment, but I'm curious to see your results...
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Yes it is if/when having good or ultra magnificent conventional ht. even at unbelievable 100% improvement = 1/2 of very brittle = basically still way too brittle = F grade.

dirc said:
If I was trying to make a high hardness stainless chopper, I'd be looking at aeb-l, or magnacut for higher edge retention
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Neither aebl nor magnacut nor V4E with conventional ht at 65rc will get a grade A on test

dirc said:
BluntCut MetalWorks BluntCut MetalWorks please share results - I'm curious if you can get ANY geometry on s125v which withstands chopping abuse
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I am confident ht6 65rc s125v would pass chopping test at 18dps. I'll also make another s90v chopper aim for 66rc and will test at 15dps. Will check inv to see if I've enough 15v for a 69rc chopper take chopping test at 18dps too.
 
bluntcut said:
Preliminary test at conservative 20dps (instead of 18 dps) and at 70% chopping intensity. Will do full 18dps test video soon...

Under 30x loupe - Apex lost some carbides from chopping Argentine Lignum Vitae.

Hi-res image

EoTRHIZ.jpg
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Bluntcut, it's been a while since I have kept up with your work, good to see it's still going strong. Also, that blade design is strangely attractive. Nice work.

Now to the test. I don't think there are predictable results these days, but I would say that considering the compressive force of chopping, the higher Rc should take it well initially. The question would be, over time with off angle hits doing micro damage to the edge, to see how long before you blow chunks off the blade. Also, a quicker route to that failure is trying it on bone. Just some ideas. Good work.
 
Cobalt said:
Bluntcut, it's been a while since I have kept up with your work, good to see it's still going strong. Also, that blade design is strangely attractive. Nice work.

Now to the test. I don't think there are predictable results these days, but I would say that considering the compressive force of chopping, the higher Rc should take it well initially. The question would be, over time with off angle hits doing micro damage to the edge, to see how long before you blow chunks off the blade. Also, a quicker route to that failure is trying it on bone. Just some ideas. Good work.
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Yes and also it's inevitable edge subject to high lateral force chopping, especially repeated in same area of interaction/impact. Given specs of this blade, conventional knowledge mostly expect it will exhibits extreme brittleness (jokingly blade of glass). 18dps edge chops pork rib bone is in test criteria, since currently it is 20dps - I tested (albeit quite control) chop beef rib bone:

rttmsfI.jpg


Next I will test it according to original test criteria. Regardless of pass or fail, this blade will continue with final HT6 processes, where it will gain yield strength while gave up some toughness. Then I will perform another test against test criteria. If it passed, will gradually lower edge angle until straddling/spanning failure threshold/limit.
 
18dps is already a steep angle for a steel not meant for hard use. It will be interesting to see how the edge fails when you go thinner.
 
I over ground the edge, it is a thin 18dps where behind edge thickness is less than 0.010" and belt-ground-edge shoulder is around 0.022-0.023" thick. So equivalent behind edge thickness is to about 0.018" thick. A good probability, this edge geometry would buckle when chopping Argentine Lignum Vitae

SeMWEJY.jpg


Thoughts/advises?
 
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