MPK-Ti


A picture of the MPK-Ti (bottom) alongside a SOG SEAL 2000 :

mpk and sog
	seal

Specifications

The MPK-Ti, multi-purpose knife from Mission Knives was made by stock removal out of 1/4" Beta-Titanium hardened to 47 HRC. The MPK-Ti has a seven inch blade but due to the low density of Ti weighs only 250 g. The primary grind is high full flat of about 3.5 +/- 0.3 degrees per side . The edge is efficiently ground for a heavy duty knife, ranging 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.

Battle of the Navy Seals

Having both the SOG SEAL 2000 and MPK-Ti on hand, a comparison was made over a wide range of tasks, including cutting of various materials, chopping, prying and examining the corrosion resistance (for extended details of the work see the review of the SOG SEAL 2000) .

The following table presents a visual summary of the work done. The superior description was used when the performance advantage was less than two to one, vastly superior when the advantage greater, and similar when the difference took care to notice (less than 25%).

Qualitative comparison overview of Mission MPK-Ti and SOG SEAL 2000
Aspect MPK-Ti SOG SEAL 2000
straight edge cutting ability vastly superior  
edge retention similar
impaction   superior
chip resistance vastly superior  
serrations cutting ability vastly superior  
edge retention vastly superior  
durability   superior
handle ergonomics superior  
versatility superior  
durability vastly superior  
Blade material corrosion resistance vastly superior  
ductility vastly superior  
impact toughness vastly superior  
impaction resistance   vastly superior
magnetic signature vastly superior  
point penetration similar
strength slightly superior  
Miscellaneous chopping similar
prying slightly superior  

In short, the SOG has only one advantage over the MPK-Ti which is that the steel is harder which gives it more resistance to impaction (denting). When both blades are whacked into hard objects (hard meaning, hardened metals, bone, rock, etc.) , the MPK-Ti will dent to a greater depth. Note when the lower weight of the MPK-Ti is taken into account, its efficiency over the SOG SEAL is even greater than the above table indicates.

Beta-Ti

There are many Titanium knives on the market. Just as with steel, the type of Titanium is critical to the performance of the knife. The Beta-Ti used by Mission is hardened to 47 HRC, significantly harder than many other grades of Titanium which gives the blade much greater strength and the edge much greater ability to maintain sharpness.

edge retention

The edge retention in corrosive environments of Beta-Ti is high as even some of the more corrosion resistant stainless steels lose sharpness quickly when exposed to salt water]. Beta-Ti also strongly resists chipping and fracture in general, so it can hold up better in extreme uses than many current high carbon stainless steels as noted in the above. However, On hemp rope cutting, the MPK-Ti's primary straight edge holds its edge only about half as well for example as a quality production steel blade like the CU/7 from Becker Knife and Tool. When chopping on hard woods, the MPK-Ti will also see edge roll before the steel blade.

However, Mission has given the MPK-Ti superb rope cutting abilities and a very long edge retention for such types of cutting with the couple of inches of reverse waved serrations. Due to the shallow angle used on these serrations and the very aggressive manner in which they are sharpened, the cutting ability and edge retention is extremely high. After 254 cuts through hemp rope the serrations only needed a few more pounds of force continue to make cuts, much greater edge retention than many high end plain edge blades. Essentially then for maximal edge retention, the primary straight edge is kept at a high polish which is easily obtained and this is used for all chopping and general push cutting work, and any slicing done with the serrations which have extreme edge retention and very high cutting ability with a smooth cutting action due to the geometry and nature of the very high quality initial sharpening by Mission.

The main drawback of the Beta-Ti sharpening wise is that it doesn't respond as well to aggressive stone finishes. When the plain edge on the MPK-Ti was reground with a 100 grit AO belt, its aggression and edge retention didn't increase as much as can been seen with various steels. However as noted in the above, the serrations on the MPK-Ti are excellent at such work and will readily outlast many steels even with aggressive coarse edges. The Beta-Ti also tends to gum up ceramic hones and be difficult to clean.

overall durability

There are issues with denting with the MPK-Ti due to the low hardness. In high stress accidental impacts off of hard inclusions the Ti indents more readily than harder cutlery steels. However some of these harder cutlery steels are very brittle, so even though they are much more resistant to being dented, they can suffer more damage because they fracture. Chipping due to fracture is a serious problem and can lead to extensive damage quickly. As an example, when WB from Strider Knives, made from ATS-34 at 60/61 HRC was hacked into a concrete block the steel fractured readily which quickly lead to loss of material going up into the primary grind. When subjected to similar and even much harder impacts, the MPK just suffered denting, no chipping and no significant crack propagation.

Beta-Ti is far more flexible than most steels and thus can readily handle tasks which leave many steel blades broken. For example, one inch of the tip of the MPK-Ti was inserted into a piece of seasoned 4x4, by hitting the the butt with a hammer, and the blade was leveraged sideways until the handle was about parallel to the wood, an extreme bend, at which point it broke free of the 4x4. The tip had taken a permanent bend of about 25 degrees, however it had resisted breaking. The bend was restored with a little hammering and reverse prying.

The main body of the blade also shows the same class of durability. The knife was subjected to loads of 210, and then 250 lbs applied to the center of the handle, with the blade inserted the full length of the clip into a tree). The blade flexed significantly but returned to true. It was then bent until the handle came close to touching the tree and still resisted fracture, though it finally took a visible permanent bend. As an extreme performance limit, a 210 lbs individual stood on the handle while the blade was inserted in the tree and started bouncing on the handle, and pressing down leveraging off of branches. It took half a minute of this repeated flexing for for the blade to finally break, leaving about an inch and a half of the tip in the tree. When the blade finally gave way, it didn't crack, but actually ripped.

Compare this performance to results obtained with the Becker Combat Bowie. Prying in wood to the same depth, the Becker took a tip break under a much lower angle, and much lower load. With the Becker just wrist torque was necessary to break the tip, while the MPK-Ti took a two handed pull drawing on the shoulders and back to bend the blade down against the wood. The tips were of similar cross section on both knives. The Becker Bowie was also unable to take a load of 250 lbs, and snapped before the full load could be applied.

The point could be made of course that the MPK-Ti is more expensive than the Becker, however does the MPK-Ti fare in regards to toughness vs other knives in a similar price range. Well specifically the Strider WB broke under heavy prying with no significant prying, suffering brittle failure almost immediately. Several customs from Kevin Mcclung [ref : 1, 2, 3] made from O1-tool steel have also exhibited catastrophic failure under much lighter loads than what the MPK-Ti took without significant permanent harm. Specifically note the p-ATAK which shattered into multiple pieces during the prying is the same weight as the MPK-Ti.

Note in the above prying, the MPK-Ti was driven into the tree point first by pounding on the pommel with an Estwing framing hammer (22 oz). The fully enclosed Hytrel grip held up well to the extended hammering, and only broke after more than a couple of dozen full very heavy swings from the hammer. It was subjected to about a couple of dozen more hits on the bare tang to drive the knife to the required distance into the tree. The grip, while it did crack, didn't explode, but more ripped and tore. It was still very functional even after the pounding.

A shot of the MPK-Ti after the above work :

damaged
	MPK-ti

Note even after the extreme abusive prying the blade simply suffered a broken tip, the main body of the blade is uncompromised and still useful at a variety of tasks. Note there was no propagation of the break throughout the knife, no gross shattering which can be readily seen with various stainless and carbon steel blades.

As a final check on relative toughness, the remaining parts of the Becker Bowie, Mission MPK-A2 and MPK-Ti were subjected to extensive hammering. With the MPK-A2 on a 4x4, light hits with a ball-pien hammer induced heavy fracture, large pieces (greater than 0.5 cm squared) broke away after just eight light pops, elbow snaps. The Becker Bowie took a dozen of such hits and then a dozen more full swings from the shoulder with no problems.

With the Becker on a smooth beach rock, a couple of elbow pops on the same point of impact induced several large pieces of the blade to break away (a cm squared). A dozen full hits on another section of blade failed to induce more fracture. One the rock, the Mission-A2 again suffered damage faster than the Becker Bowie and to a larger extent. The MPK-Ti took two dozen hits on the 4x4 and two dozen on the rock without effect. Further, additional impacts were focused right on the edge of the knife, and full power swings still could not cause fracture. Eventually the edge was actually thinned out by cold working, and the metal suffered ductile failure.

In short, the Becker steel showed it was significantly tougher than the Mission-A2 impact wise, which was also seen before (see the reviews for more details [MPK-A2, Becker Bowie] and the MPK-Ti was clearly in another higher class.

Overall

The MPK-Ti is an efficient cutting tool, with an impressive durability and functionality in regards to handling very heavy work such as hammering, digging and prying, exceeds many steel blades in this respect. The serrations also stand out with very high performance cutting ability with extreme edge retention on ropes and such. The handle is also well designed, a fully enclosed grip, providing both thermal and electrical insulation, and has a decently "grippy" surface and ergonomic shape for high comfort and grip security.

There are some drawbacks due to use of Ti however; the low weight and reduced hardness. Because the MPK-Ti is fairly light and neutral in balance it isn't an efficient chopping tool compared to something of similar size (but much heavier) like the Camp Tramp . The ~47 HRC blade also means that it will indent more readily than the higher hardness cutlery steels, which can be a problem on accidental hard contacts. It also doesn't respond as well to coarse finishes.

Mission also offers the MPK in A2 tool steel. That version is significantly more blade heavy and a much more efficient chopper. The harder tool steel also has significantly greater resistance to denting and edge roll and responds well to very fine edges. Its only drawback is that it isn't as tough as the Beta-Ti in regards to resisting fracture from impacts, and not as flexible. It also doesn't have the near invulnerability to corrosion of Beta-Ti alloy.

Comments and reference

Comments can be sent to : cliffstamp[REMOVE]@cutleryscience.com or posted to :

There is also a website for Mission Knives, which contains many articles on the blades as well as detailed design and materials information.


Last updated : Wed May 5 13:24:04 NDT 2004
Origionally written : Fri Jun 6 13:56:57 NDT 2003
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