Chopper test & arms exercise

[BluntCut MetalWorks]

Fun & giggle thread...

Time to test my experimental chopper: 52100 1/4" thick, 21" OAL, 12" blade, 2.5" wide, super quenched, 56rc, 13dps, 0.025" behind edge, 2 handed figured Sapele handle. Partial tang because my oven is not long enough.

I planned to chop through a 13" dia Eucalytus tree trunk. But end up chopped through a 18.5" dia trunk. 2 hrs and 15 minutes of sweat, along with 3 blisters on each hand. Edge still slice newsprint afterward. Instead of my daily open water swim, I double the amount of work-out with this chopping exercise.

My camera ran out of battery after 90minutes. Sensible thing, I won't upload long & boring videos to youtube.

 

[JayGoliath]

It does look like the head is heavier/wider.

More pics please. Interesting choppa.

 

[BluntCut MetalWorks]

Yep, the head was on the heavy side. After my long outing, I reprofiled the blade to pull the balance back to around 2" in front of the handle and conducive to higher velocity swing. Now its weight 1#13oz.

Pic along with my 52100 58.5rc bladesports spec chopper w/ White Teak Burl.

It does look like the head is heavier/wider.

More pics please. Interesting choppa.

 

[philllll]

Awesome knife!

 

[tiguy7]

Paul Bunyan watch out!

 

[Camber]

Nice work Bluntcut. One day you'll have to sell me a chopper

 

[BluntCut MetalWorks]

Thanks Phil.

Awesome knife!

Yeah I know, my choppers would be a little large for Paul Bunyan's back pocket EDC

Paul Bunyan watch out!

Thanks C, What? expand your cool collection including Joe's choppers. Heheh, of course, there is always room for one more I plan to make two more similar choppers (with a 1" longer partial tang) and with edge hardness 59 & 61+ (spine ~52rc). Hopefully, won't end up with little & mondo 'chippers'

Nice work Bluntcut. One day you'll have to sell me a chopper

 

[Camber]

Can't wait to see them. This is a really attractive design!

 

[Chris "Anagarika"]

BF keep crashing when I want to reply

2 hrs chopping & still slice newsprint @ 56HRC? Hope I am not dreaming

 

[BluntCut MetalWorks]

Thanks Chris,

This relatively green Eucalytus (tree fallen 2 months ago) is much harder than seasoned red-oak. The last 30 minutes of chopping was consisted of throwing the chopper edge toward the trunk, hope for a hit/cut. Majority of strikes were lateral/glacing type. I found wood chopping hardly degrade refined edge keenness. So 56rc is a safe choice for large choppers. At 58+rc, if a small portion of the edge caught & steered by a small pin knot, while the rest of the blade keep going or glancing away, well exit mode = a large chip. Where 56rc would bend/ripple and exit. I rather peen my edge back to action than disappointed with ruined/chipped edge. That said, I will use diff ht params for my next choppers, hopefully 59 & 61rc won't be a dual disappointments.

These choppers were super quenched and they ain't suck according to my biased self I happened to see SQ flametard got personal, so I replied http://www.bladeforums.com/forums/s...-compressive-strength?p=14390305#post14390305

BF keep crashing when I want to reply

2 hrs chopping & still slice newsprint @ 56HRC? Hope I am not dreaming

 

[chiral.grolim]

... That said, I will use diff ht params for my next choppers, hopefully 59 & 61rc won't be a dual disappointments...

I believe Swamp Rats were spec'd to 59-61Rc and testimony has been similar to that presented here - newsprint-cutting edge after extensive woodwork, chopping. That said, Swamp Rats tend to be thicker behind the edge to resist that lateral-flex that could lead to major-chip. Axes/hatchets, also much thicker, are commonly softer that 56 Rc but I've experienced similar results of maintained sharpness after much chopping. You have tried this test with non-SQ'd blade? Keep up the good work :thumbup:

 

[BluntCut MetalWorks]

Thanks.

My 58.5rc 52100 15" oal chopper did fine too https://www.youtube.com/watch?v=h0cuqWP9VLo
but 2 handed at 21" oal at 59rc, a major mis-strike into knot was resulted in 3mm pain/chip (0.025" behind edge thickness).

I've tried Fallkniven NL2 Odin (laminated vg-10), macassar+no-name-homedepot machete. One full chop cross grain into seasoned white oak or eucalyptus log would end up with a chip & dent respectively. Chop into a knotty seasoned pine, at angle at the end of the log, where wood would blow out & glance the edge away, except a small area of the edge caught & steer into the log by a pin knot. Which the same as being laterally sheer by a plier, well smartly I swing gently, otherwise my $450 odin would worth $100 afterward. Now Odin/NL2 is only around 13" OAL and quite thick (convex grind & edge).

If swamp rats reprofile to 13dps and 0.025" behind edge, I don't think it would does well against scenarios outlined above. If I increase my chopper edge thickness to 0.04, yeah I probably can push hardness to 62+RC. But increased thickness would decrease penetration and efficiency for 99% of the usage time. Not a good trade off IMO and knowing that worse case scenario could malfunction the chopper when in need. Right, confident in your tools allow you to accomplish tasks at hand, rather than that nagging fear of breakage.

I am comfortable with trade for toughness & confidence didn't compromised much edge retention. Sure, it wasn't fun test & keep increase the temper temperature until, failure mode is certain for up to 1cm blade height is bend/ripple/deform not chip/blow-out.

I inherited 2 felling axes (prob 50+yrs old) ~59rc heads - 26 & 34" handle. They can't get thinner than 0.03" behind thickness for scenario above w/o chipping. Gave the double-edge axe away - I was too nervous swinging that thing.

All in all, when come to chopping - complete the task is far more important than triviality high hardness edge retention. Same perspective apply to SQ vs std ht, doesn't matter which way. I am working toward 62+rc 52100 chopper 13dps 0.025" or less edge thickness and pass the test above. If I succeed with SQ, cool. Whence std ht 52100 road ended around 58-59rc.

I believe Swamp Rats were spec'd to 59-61Rc and testimony has been similar to that presented here - newsprint-cutting edge after extensive woodwork, chopping. That said, Swamp Rats tend to be thicker behind the edge to resist that lateral-flex that could lead to major-chip. Axes/hatchets, also much thicker, are commonly softer that 56 Rc but I've experienced similar results of maintained sharpness after much chopping. You have tried this test with non-SQ'd blade? Keep up the good work :thumbup:

 

[Chris "Anagarika"]

Thanks.

My 58.5rc 52100 15" oal chopper did fine too https://www.youtube.com/watch?v=h0cuqWP9VLo
but 2 handed at 21" oal at 59rc, a major mis-strike into knot was resulted in 3mm pain/chip (0.025" behind edge thickness).

I've tried Fallkniven NL2 Odin (laminated vg-10), macassar+no-name-homedepot machete. One full chop cross grain into seasoned white oak or eucalyptus log would end up with a chip & dent respectively. Chop into a knotty seasoned pine, at angle at the end of the log, where wood would blow out & glance the edge away, except a small area of the edge caught & steer into the log by a pin knot. Which the same as being laterally sheer by a plier, well smartly I swing gently, otherwise my $450 odin would worth $100 afterward. Now Odin/NL2 is only around 13" OAL and quite thick (convex grind & edge).

If swamp rats reprofile to 13dps and 0.025" behind edge, I don't think it would does well against scenarios outlined above. If I increase my chopper edge thickness to 0.04, yeah I probably can push hardness to 62+RC. But increased thickness would decrease penetration and efficiency for 99% of the usage time. Not a good trade off IMO and knowing that worse case scenario could malfunction the chopper when in need. Right, confident in your tools allow you to accomplish tasks at hand, rather than that nagging fear of breakage.

I am comfortable with trade for toughness & confidence didn't compromised much edge retention. Sure, it wasn't fun test & keep increase the temper temperature until, failure mode is certain for up to 1cm blade height is bend/ripple/deform not chip/blow-out.

I inherited 2 felling axes (prob 50+yrs old) ~59rc heads - 26 & 34" handle. They can't get thinner than 0.03" behind thickness for scenario above w/o chipping. Gave the double-edge axe away - I was too nervous swinging that thing.

All in all, when come to chopping - complete the task is far more important than triviality high hardness edge retention. Same perspective apply to SQ vs std ht, doesn't matter which way. I am working toward 62+rc 52100 chopper 13dps 0.025" or less edge thickness and pass the test above. If I succeed with SQ, cool. Whence std ht 52100 road ended around 58-59rc.

Totally agree that completing the task is important in chopper. So the SQ might be to increase wear resistance at high hardness. If not, then std HT then. Got your point. It is also a direct reply to Jim's point: make a knife to suit the purpose. :thumbup:

 

[chiral.grolim]

My 58.5rc 52100 15" oal chopper did fine too https://www.youtube.com/watch?v=h0cuqWP9VLo
but 2 handed at 21" oal at 59rc, a major mis-strike into knot was resulted in 3mm pain/chip (0.025" behind edge thickness).

I've tried Fallkniven NL2 Odin (laminated vg-10), macassar+no-name-homedepot machete. One full chop cross grain into seasoned white oak or eucalyptus log would end up with a chip & dent respectively. Chop into a knotty seasoned pine, at angle at the end of the log, where wood would blow out & glance the edge away, except a small area of the edge caught & steer into the log by a pin knot. Which the same as being laterally sheer by a plier, well smartly I swing gently, otherwise my $450 odin would worth $100 afterward. Now Odin/NL2 is only around 13" OAL and quite thick (convex grind & edge).

If swamp rats reprofile to 13dps and 0.025" behind edge, I don't think it would does well against scenarios outlined above. If I increase my chopper edge thickness to 0.04, yeah I probably can push hardness to 62+RC. But increased thickness would decrease penetration and efficiency for 99% of the usage time. Not a good trade off IMO and knowing that worse case scenario could malfunction the chopper when in need. Right, confident in your tools allow you to accomplish tasks at hand, rather than that nagging fear of breakage.

I am comfortable with trade for toughness & confidence didn't compromised much edge retention. Sure, it wasn't fun test & keep increase the temper temperature until, failure mode is certain for up to 1cm blade height is bend/ripple/deform not chip/blow-out.

I inherited 2 felling axes (prob 50+yrs old) ~59rc heads - 26 & 34" handle. They can't get thinner than 0.03" behind thickness for scenario above w/o chipping. Gave the double-edge axe away - I was too nervous swinging that thing.

All in all, when come to chopping - complete the task is far more important than triviality high hardness edge retention. Same perspective apply to SQ vs std ht, doesn't matter which way. I am working toward 62+rc 52100 chopper 13dps 0.025" or less edge thickness and pass the test above. If I succeed with SQ, cool. Whence std ht 52100 road ended around 58-59rc.

Your Fallkniven suffered a major chip? That surprises me given the old Noss D-test of the Fallkniven A1 that has since been re-uploaded: https://www.youtube.com/channel/UCReKyb0rO1E2Leamipn7Yfg/videos
Here is it chopping pressure-treated lumber:

[video=youtube;PKKLTdW8ijw]https://www.youtube.com/watch?v=PKKLTdW8ijw[/video]

And here is a SwampRat Chopweiler thinned-out by the silverback bladesports champ for user worldwood - not heavy chopping but a simple demonstration to encourage confidence:

[video=youtube;sS0D-AAXKR8]https://www.youtube.com/watch?v=sS0D-AAXKR8[/video]

I've also seen more than one video showing BRKT's suffer massive chips/rippling, either too thin or bad HT for the geometry and intended use. So yeah, definitely need to balance high-performance geometry with confidence of durability :thumbup: keep pushing that envelope. And hopefully you'll someday be able to get one of your SQ'd 52100 blades tested via etching and SEM to determine if your theories regarding the impact on microstructure are accurate.

 

[BluntCut MetalWorks]

All those yt tests were not involved lateral sheering (as I described in my prev post). Perhaps, easier to see by clamp the blade on a vise, use a plier to try laterally sheer a chunk out of the edge (maybe 3-6mm deep pinch). Examine the failure mode.

Most 5+" Fallkniven knives are very thick behind the edge - iirc my NL2 convex edge was at least 0.04" at 3mm up from the apex. Yep, it was just bounce off dry hardwood cross grain. VG-10 @ 60rc isn't tough at all even laminated with 420J.

My order of Nital 3% got onto a slow route - been waiting for mfg (RicaChemical) next batch of nital kitting. Looking forward, to visual grain & carbide & some microstructure images down to around 5-10um via my cheap 400x (~50linear) usb microscope.

 

[chiral.grolim]

All those yt tests were not involved lateral sheering (as I described in my prev post). Perhaps, easier to see by clamp the blade on a vise, use a plier to try laterally sheer a chunk out of the edge (maybe 3-6mm deep pinch). Examine the failure mode.

Most 5+" Fallkniven knives are very thick behind the edge - iirc my NL2 convex edge was at least 0.04" at 3mm up from the apex. Yep, it was just bounce off dry hardwood cross grain. VG-10 @ 60rc isn't tough at all even laminated with 420J.

My order of Nital 3% got onto a slow route - been waiting for mfg (RicaChemical) next batch of nital kitting. Looking forward, to visual grain & carbide & some microstructure images down to around 5-10um via my cheap 400x (~50linear) usb microscope.

As you described, "lateral sheering" will occur whenever the blade edge is turned aside as pressure is applied, like an "edge-flex" test, and can result in rippling - large chips occur when the ripple-deformation exceeds the yield-point of the steel. I am not arguing that VG10 is tough steel (and the 420 laminate doesn't reach that close to the edge anyway) or that the geometry isn't heavy at the expense of penetration-performance, only that your Fallkniven should not dent/chip/flex within the 15-20 dps edge-bevel as you describe. If you grind it thinner like your chopper maybe it would fail, but I'd want to see it happen. Lots of companies make their knives excessively thick not because they'd actually fail otherwise but because they're stacking the odds in their favor and not many people grind the blades down to where they'll actually perform. That's why we turn to guys like you who maximize performance through geometry and then work the steel to match :thumbup:

Here's another video of a really thinned-out Swamp Rat, albeit smaller, being used in ways that could induce "lateral sheering" yet suffers no ill. People buy Swamp Rat because they are confident in the performance, people will buy your knives for the same reason. Looking forward to those micrographs

[video=youtube;pH2xKkAMi6w]https://www.youtube.com/watch?v=pH2xKkAMi6w[/video]

 

[BluntCut MetalWorks]

Thanks for the encouragement. I just want brought up possible reasons behind many stories mysterious broken large blades edge.

I scanned your linked yt video. Let me try to describe the scenario again, which is not an 'edge-flex'.

An edge enter the wood at angle of entry - at zero degree edge relative to spine. A pin knot steer part of the edge -15degrees(into) or caught the edge on 0 degrees, while the rest of the edge deflected + 15-60 degrees(away). If the blade momentum keep going away, the steered or caught part must yield <= thus bend/ripple/chip. Hence my analogy of a plier ripping out part of the blade. Smaller blades momentum too small to see/encounter this affect, unless try to hard chop a small brass rod at 20-30degrees angle with a chisel grind, where the blade deflected and keep going while part of the edge stuck behind.

'Edge-flex' is more/less a deflection scenario. Over 95% of with grain wood batoning mostly involve edge shoulder than the edge itself.

As you described, "lateral sheering" will occur whenever the blade edge is turned aside as pressure is applied, like an "edge-flex" test, and can result in rippling - large chips occur when the ripple-deformation exceeds the yield-point of the steel. I am not arguing that VG10 is tough steel (and the 420 laminate doesn't reach that close to the edge anyway) or that the geometry isn't heavy at the expense of penetration-performance, only that your Fallkniven should not dent/chip/flex within the 15-20 dps edge-bevel as you describe. If you grind it thinner like your chopper maybe it would fail, but I'd want to see it happen. Lots of companies make their knives excessively thick not because they'd actually fail otherwise but because they're stacking the odds in their favor and not many people grind the blades down to where they'll actually perform. That's why we turn to guys like you who maximize performance through geometry and then work the steel to match :thumbup:

Here's another video of a really thinned-out Swamp Rat, albeit smaller, being used in ways that could induce "lateral sheering" yet suffers no ill. People buy Swamp Rat because they are confident in the performance, people will buy your knives for the same reason. Looking forward to those micrographs

[video=youtube;pH2xKkAMi6w]https://www.youtube.com/watch?v=pH2xKkAMi6w[/video]

 

[BluntCut MetalWorks]

The scenario I described was learnt the hardway...

I learned from this chopper, after chopped boulder & nail fine but knotty pine ... took a little time to investigate to realized simple physics.

SQ 52100 18.5" oal, 62+rc, 12dps, 0.02 behind thickness... blade got re-grinded multiple times. Same result with seasoned knotty pine. Chop at the end of the log at around 45 degrees entry, where wood blow-out but edge caught & or steered inward by knot.

 

[chiral.grolim]

Thanks for the encouragement. I just want brought up possible reasons behind many stories mysterious broken large blades edge.

I scanned your linked yt video. Let me try to describe the scenario again, which is not an 'edge-flex'.

An edge enter the wood at angle of entry - at zero degree edge relative to spine. A pin knot steer part of the edge -15degrees(into) or caught the edge on 0 degrees, while the rest of the edge deflected + 15-60 degrees(away). If the blade momentum keep going away, the steered or caught part must yield <= thus bend/ripple/chip. Hence my analogy of a plier ripping out part of the blade. Smaller blades momentum too small to see/encounter this affect, unless try to hard chop a small brass rod at 20-30degrees angle with a chisel grind, where the blade deflected and keep going while part of the edge stuck behind.

'Edge-flex' is more/less a deflection scenario. Over 95% of with grain wood batoning mostly involve edge shoulder than the edge itself.

Oh i get it, and the same physics are at play in an edge-flex test only slower, you don't need pliers to recreate the effect. Here is a video of a guy batonning a CS Leatherneck through some knotty pine. His efforts cause plastic-deformation as the edge and primary bevel are deflected around a knot, yet rather than attempt to peen/bend the blade true (which might not help anyway, the plastic deformation having necked & work-hardened the steel) he carries on pounding until the flex exceeds the yield-point and a MAJOR fracture occurs. The same thing can happen when chopping with a thin edge (as some BRKT videos have shown) only at a quicker pace:

[video=youtube;SiVeNOpvYMs]https://www.youtube.com/watch?v=SiVeNOpvYMs[/video]

The scenario I described was learnt the hardway...

I learned from this chopper, after chopped boulder & nail fine but knotty pine ... took a little time to investigate to realized simple physics.

SQ 52100 18.5" oal, 62+rc, 12dps, 0.02 behind thickness... blade got re-grinded multiple times. Same result with seasoned knotty pine. Chop at the end of the log at around 45 degrees entry, where wood blow-out but edge caught & or steered inward by knot.

Such a pretty handle... Might have survived at 0.030 but, like you said, loss of cutting efficiency... or did you try that and get the same result?

 

[BluntCut MetalWorks]

I didn't tried 0.03" thickness. Initially, I thought all chipping were due to ruined tempered (turned brittle) from grinding. Grinded away all chips - lost around 4mm blade width/height. Chopped huge rocks, made 2 track around 5mm deep and few cm long - no problem. Back to knotty pine, chips after chips - yeah I was not happy. Later on, while digging out embedded chips, my aha & duh moment to realized the simple physics involved.

From probably 1K of chops and tracked various interaction params & results. I conclude 0.023 - 0.026 thickness; 12-15dps refined edge; 55-59rc are in optimal range for choppers.

I will push the limit for my next 2 choppers: with 0.02-0.022 thick, 10-11dps, 59 & 62rc. After that, I want to make a 16" OAL chopper out of 0.24" thick D2 with sub 0.025 thick, 12dps, 61-62rc - ahem no SQ for this one but will employ alt radical ht rather use boring std. Mfg D2 toughness (probably worse for impact toughness) spec looks pathetically low at such hrc, LOL doesn't improve much at 59rc either. Failure is certain - well well sign me up for a try

...
Such a pretty handle... Might have survived at 0.030 but, like you said, loss of cutting efficiency... or did you try that and get the same result?