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Blade
geometry and NIB sharpness:
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The SOG
SEAL is 1/4" thick 440A at 56-58 RC, 1.25" wide
and 345 g. It has a sabre-flat primary grind ground at ten
degrees per side. The tip has a distal taper of 2.8
degrees per side and the dual grind nature presents a slim
profile. The edge ranges from 0.047" to 0.55"
thick behind the bevel which is ground at 26 +/- 1
degrees. The serrations are chisel ground at about 20
degrees included.
NIB primary edge :
On thread => 275 +/- 34 g
1/4" poly 1000 g load => can't make a cut
1/4" poly 1500 g load => 1.62 +/- 0.09 cm
The blade only shaves smoothly near the tip. Using just
blade weight the primary edge just scores the poly after
50 passes back and forth. The serrations are more
aggressive and cut through the poly only needing 10
passes. The serrations are very rough showing multiple
0.1-0.2 mm areas of damage under magnification, they look
ground by not polished, they just bust the thread (650 -
750 g).
The MPK-TI is also 1/4" but being TI is much lighter
at only 250 g. The primary grind is full flat and only 3.5
+/- 0.3 degrees per side . The edge ranges from
0.030" to 0.032" thick behind the bevel which is
ground at 20 +/- 1 degrees per side. The serrations are
chisel ground at approximately 15 degrees included.
NIB primary edge :
Thread => 200 +/- 14 g
1/4" poly 1000 g load => 2.15 +/- 0.27 cm
Serrations :
Thread => 305 +/- 6
The serrations are much less finished than the plain edge
and under magnification irregularities are visible similar
to what is seen on the SOG, however they are larger, from
0.2 to 0.3 mm deep. The serrations can't be pulled across
the poly when it is under 1000 g of tension. If I attempt
to pull the blade it just digs in and then violently rips
the cord suddenly.
In short, NIB, the MPK-Ti is much sharper. The SOG-SEAL
looks to be over buffed the same condition as the Recondo
I had in BG-42.
http://www.physics.mun.ca/~sstamp/knives/recondo.html
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Cutting
ability:
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Push
cutting on 3/8" hard poly, rocking cut :
SOG SEAL = 77 +/- 6 lbs
MPK-TI = 51 +/- 3
THe SOG require a much larger force showing its lower
cutting ability. With the MPK given a rank of 100, the SOG
would be 65 +/- 3. This greater performance of the MPK is
mainly due to both a higher primary grind (full flat vs
partial height flat), and a thinner and more acutely
ground edge bevel, plus a more enhanced belly.
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Chopping
ability (two fingered snap):
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MPK-Ti /
SOG Seal : 85 +/- 9
Neither blade chops well as both are close to neutral
balanced. Chopping has to be done by snap cutting with a
partial grip around the end of the handle. The performance
of the knives is very close, the difference that I saw was
just noticeable. More chopping would I am sure have
refined the relative performance of the SOG, it is under
the MPK, but just barely so. However, considering the
MPK-TI is 260 g and the SOG 345, the chopping performance
to weight ratio is horrible for the SOG SEAL. You are
carrying around a lot more weight, but it offers no
significant advantage for chopping ability because the
performance is gutted due to the thick grinds. If the
weight ratio is normalized the performance ratio becomes :
MPK-Ti / SOG Seal : 64 +/- 7
The MPK-TI is shown to be a much more efficient chopper
per weight (about 50%), which you would expect given the
higher performance cutting profile. This rank also
reflects well the rope cutting performance which you would
expect when the mass difference has been removed as they
are both just push cuts through semi-elastic material.
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Edge
retention:
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Primary
edge :
Both blades were ran through cutting trials on 3/8"
hemp rope . The cuts were slices made over 2 inches of
edge. Four trials were ran with each blade, including a
fresh sharpening which ended with a 600 grit DMT rod. The
results of the four trials were them combined. In short,
after fourteen cuts of the rope both edges had degraded to
the point where they would not slice paper (more details
will be in the respective reviews). However it should be
noted that due to the much higher cutting ability of the
MPK you ocld cut more rope at a specific leve of force.
The MPK started needing 32-34 lbs and finished at 41-42
lbs. The SOG started at 41-42 lbs and at the end needed
more than 50 lbs. Both sharpened with equal speed, the Ti
blade tended however to gum up the hones.
Serrations :
The MPK has 2" of waved serrations and started off
only needing 16-18 lbs to cut through the 3/8" hemp.
After 254 cuts the performance had only decreased to the
point that the blade now took 18-21 lbs to cut through the
hemp. This is just at the point where I could tell that it
had increased. I then did another 256 cuts through used
and dirty 3/8" poly. This finally blunted the blade
so it took 31-33 lbs to cut through the hemp. Checking the
edge under magnification, only the tops of the serrations
are worn and folded over. They protected the scalloped
edges which do most of the cutting from grinding through
the dirt left behind on the cutting block from the used
poly. A few passes on a grooved steel and the serrations
are back to cutting the hemp with 21-23 lbs.
Testing the serration pattern of the SOG revealed another
matter. It has 1.5" of serrations which are pointier
and more shallow. With over 55 lbs of force applied I
could not get a clean cut through the 3/8" hemp, it
is simply too difficult to pull the serrations through the
rope, you basically have to bust it apart. The biggest
problem is the cutting block under the rope, you have to
drive the points in far too deep to allow the scallops to
contact the rope. Walking on the rope and cutting it under
tension, the MPK would outperform the SOG about four times
to one in regards to the number of passes required under
heavy force. The MPK would constantly cut through the poly
in less than 1" or serrations while the SOG would
require ~4 complete passes.
I then tested the serrations on many types of fabric, old
jackets, jeans, sweat shirts, as well as various belts and
webbing. The MPK would constantly outperform the SOG many
times to one. The only material that I found that the SOG
would cut well was something that weak that it would be
readily torn apart. Cutting up some rubber tubing the SOG
had an advantage over the MPK, about 25%. On wood, the SOG
bites in a little deeper, but the MPK requires less force
to be pushed through, neither had a
significant advantage as a wood saw.
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Edge
durability:
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Both
primary edges were durable enough to split 1-2 year old
knotty seasoned pine and spruce. The force of the impacts
was that large that the baton (a 2" piece of spruce)
would be destroyed every few pieces of wood split.
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Point
penetration and durability:
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Phone
book, vertical stab :
MPK_TI = 656 +/- 27 pages
SOG SEAL = 707 +/- 7 pages
The SEAL was comfortable in the stab and penetrated well.
The MPK had penetration very close to the SOG but suffered
from a too square upper guard. Without enough radius, the
pressure was high and thus not comfortable causing me to
back off a little on the power of the stabs which skewed
the performance. I was actually holding the SOG handle
completely inside my grip for maximum power. Thus SEAL
outperformed the MPK in this aspect both in regards to raw
penetration (~10%) and comfort (significantly). However if
you look at the penetration from a mass point of view, the
MPK again easily jumps ahead of the SOG. The results
scaled by mass :
MPK-TI = 2.6 pages per gram
SOG SEAL = 1.9 pages per gram
This has the SEAL at 71% of the performance of the MPK-Ti.
Doing some light prying it is obvious that the SOG is
stiffer than the MPK-Ti, the critical question is what is
the behavior under high loads? To investigate this, as
well look at some other aspects I dug holes in 2x4's large
enough to fit my index and middle finger through. The
board would be dug half way through, flipped over and
completed. The stabs would be hard getting 1/2"+
penetration, and the prying to the side at done with
maximum force. Both the time it took to make the cuts as
well as the number of stabs needed was recorded. The
results :
MPK-TI = 39 +/- 13 stabs over 4.1 +/- 1.6 minutes
SOG SEAL = 46 +/- 5 stabs over 3.8 +/- 0.7 minutes
Three trials were run with the MPK, only two with the SOG,
both tips had suffered visible damage. The tip of the SOG
suffered a bend of about 5 degrees running back 1.2 cm. In
addition the very last mm of tip was bent over 45 degrees
to the side. The MPK suffered a smaller bend, under 3
degrees running back about 2 cm. Both major bends were
corrected with prying in the reverse direction. The large
bend in the extreme of the SOG tip had to be filed off.
In regards to the results, it is hard to judge digging
performance off of them because so little work was done
and the wood can vary tremendously. However from the feel
of the stabs, I can say that the MPK's point gave better
leverage as the SOG's tended to pop out more because of
its diamond-like cross section. The MPK proved more
durable taking less damage over more work.
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Handle
ergonomics and security:
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The SOG
is square, slippery where smooth and aggressive when
checkered. Nothing great in the ergonomics or security
department, however I had no real problems with the above
work. The MPK has a nice texture, not slippery but not
abrasive, the grooves help as well. The shape is a huge
improvement over the SOG. The only problems are the lack
of a radius in a few key areas.
Left to do :
-Handle security and ergonomics when wet/soaped
-handle durability
-edge durability under hard impacts
-corrosion testing
-edge testing which a re-profiled edge
-prying
-misc
Suggestions welcomed.
A picture :
http://www.physics.mun.ca/~sstamp/i...2000_MPK_Ti.jpg
Note the SOG's serrations are ground on the wrong side for
a right handed person.
-Cliff
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Mission Articles
