TAC-11 by Tom Johanning


A shot of the TAC-11 alongside a Becker CU/7 :

cu7 and
	tac-11

The knife was donated for a review by Tom Johanning.

Specifications

The TAC-11 is machined from one piece of modified A8, an air hardening tool steel tougher than A2 with lower wear resistance. According to Johanning, the "modified" refers to an additional 3% more Chromium than AISI A8. The blade has been vacuum heat treated to 57-59 RC and deep frozen between temper cycles to insure complete martensite formation.

The knife weighs 400 grams and is slighlty handle heavy, and the blade is 0.198 inches thick at the spine with a primary sabre-flat grind 0.67 inches wide, ground at 7 degrees. The edge is 0.028 (2) thick through the primary ground at 30 (1) degrees per side, and 0.035 (2)" through the tip ground at 42 (2) degrees per side.

The guards for example are 0.75" wide, which reduces the contact pressure significantly. The grips is also nicely swelled, is curves from about 0.75" in thickness at the ends to 1.1" in the center. The grip has a working length of around 4 inches.

Stock testing

The edge was well formed, no light reflection, 10x magnification revealed some "tooth" left to the blade at a level of about one thousand of an inch deep near the choil, with the polish running slightly higher towards the tip, the teeth were about half as deep as those near the choil. With the as supplied edge, the TAC-11 was fairly low on thread and 1/4" polypropylene rope. Taking 320 (20) grams to cut the thread and 6.0 (4) centimeters of edge to cut the poly on a two inch draw under a 500 gram load. This is fairly low initial sharpness so some light work was doing using edge trailing honing on chromium/aluminum oxide loaded leather (ten passes per side for each run) and the sharpness checks repeated :

Initial edge performance of the TAC-11 and response to stropping using light thread as a testing medium
Initial performance After 1st stropping After 2nd stropping
grams grams % gain grams % gain
320 +/- 20 240 +/- 32 25 +/- 4 190 +/- 12 21 +/- 3

The push cutting ability strongly increases and just a minute on a loaded leather strop increases the performance to about double and the blade would now shave a little at the end. However as with extended stropping of this type slicing aggression is often lost which was the case here as seen on the poly results :

Initial edge performance of the TAC-11 and response to stropping using quarter inch poly cord as a testing medium
Initial performance After 1st stropping After 2nd stropping
500 g 1000 g 500 g 1000 g 500 g 1000 g
6.0 (4) 2.3 (2) NA 1.6 (1) NA 1.6 (2)

Note the behavior is not linear with applied load, there is a critical point necessary to allow the blade to bit and if the tension is lowered below this then the edge will just score it after a full pass as the aggression has been reduced to essentiall zero. In short, the initial edge is sharp enough to handle precision cutting like light cord, and can be raised to a fine shaving finish with just a little stropping.

Moving beyond sharpness and looking at cutting ability as influenced mainly by edge angle, the TAC-11 whittled points on a one inch hardwood dowel and took 36.3 (4) slices to make a point. This is rather low due to the geometry which is optimized for a high level of durability.

The TAC-11 performed well on on the phone books stabbing getting 723 (6) pages on a hard verticla stab. It has a strong combination of a thin tip, decent mass, and a secure grip which allows maximum thrust. The grip was for the most part comfortable, however the square nature of the guards/talons did make the occasional impact uncomfortable. It also readily dug a hole in 2x4's with 24 (6) stabs and in 2.6 (6) minutes. After the digging the tip had deflected, 2.0 (5) degrees through 5 millimeters . The tip was restored to straight by just stabbing into the wood and bending it in the opposite direction.

Kitchen

For light use the TAC-11 is awkward to use because of the guard which interferes with a choked up grip on the blade (peeling vegetables for example). As well it is easily out cut by most kitchen knives because of its much more obtuse and thicker geometry. While it can handle such tasks, you have to use more force doing the cutting to force the thicker blades through the vegetation, but you are still only talking about a few pounds, the real problem is with the guards hindering grips. The blade cuts various meats with much greater ease, which you would expect as they don't exert as much binding force on a blade so the only concern is sharpness. It excels in harder applications such as disjointing meat due to the very robust edge, and the pommel is an excellent hammer and readily breaks up ice, crushes nuts and so forth.

Heavy wood work

The TAC-11 was used for felling various small trees (up to 3" in diameter), limbing them out, cutting them up into foot long sections and splitting them into a minimum of four sections. The trees were mainly Pine (all the larger ones were), with some Spruce, Juniper and Birch. Chopping was done with both a full grip, and a partial grip two fingered grip at the end of the handle. It was also compared to the Wildlife hatchet, on fresh cut Pine about three inches in diameter using a partial grip the TAC-11 had about 21 +/- 2 % of the chopping ability of the hatchet. However the abrasion of the handle when used in a partial grip formed a blister quite quickly (after 105 chops, skin was torn). Gloves would be necessary for such extended work.

The low chopping ability of the blade is mainly due to the handle heavy balance which prevents any buildup of power in the swing. Since the TAC-11 has excellent lashing points, it was turned into a makeshift bill hook out of it by attaching it to a pole, Mike Spinak's work was a valuable resource. The TAC-11 now became a very proficient tool to limb out trees, fell small saplings and in general hack apart wood. With a decent handle you can easily get the same class of performance as a decent hatchet, so you are looking at a many to one increase over just using the blade alone. Considering the performance gained, it would be worth it to carry a decent handle along with you if you intended to go the one knife route, though it would not take much to create one at a camp site.

Heavy tip work

The TAC-11 was used to split some boards and various small scrap lumber, as well as some seasoned Pine, Spruce and Juniper. For the smaller wood this is easily accomplished with just a chop, for the larger wood you will need a makeshift mallet of some kind, another piece of wood will do. During this work I became curious as to how it compared to a few other blades in regards to penetration on wood. The above table of the phone book stabbing does represent its ability well on certain types of materials, but wood tends to split which means that there is more achieving strong penetration than just a slim tip, a wedging design could actually be of more benefit.

Light stabs on one inch boards easily drove the point through the boards and would split them nicely, however the blade would only get 1.2 +/- 0.1 inches in 2x4's even on heavy swings and this would not split the wood. A heavier knife such as the Busse Battle Mistress would induce a large crack in the two by four on a similar hard stab and would split it then with a light twist.

For comparison, ATC spike 'Hawk would split two 2x4's on top of each other, and another piece of board underneath. It would almost split three 2x4's, it would have probably done this when NIB as over one quarter of an inch has been filed off from the spike during very heavy tip work, breaking concrete blocks and the like.

Heavy edge work and general extreme use

To have examine durability and check the difficulty of work done by Rob Simonich on one of his knives, the TAC-11, a SOG SEAL and a Paratrooper machete from Martindale were used to cut up some tension bar using a 22 ounce Estwing hammer to drive the blades through the mild steel bar. The SOG SEAL broke on the second hit, which was very light, and the bar was only slightly scored. The Martindale machete showed not significant damage to the blade aside from some edge denting, but the vibration did split the handle after just a few hits. With the TAC-11 I took it easy on the first cut, it took more than a dozen hits, but the second was only ten, and the last cut was just eight. The cutting was performed on a concrete step, and the bar was bouncing on the heavy impacts which made it worse on the knife. After all the cutting, the spine was impacted from the heavy hammer hits, and the edge just blunted. No gross damage of any kind. Here is a shot :

tension bar

Grip

The two most positive features of the grip are the large swell of the Micarta slabs and the very wide guards/talons. The swell rests nicely between the index and middle finger and fills the hand nicely. The large guards/talons both increase comfort in regards to impacts and specifically in regards to the pommel, increase functionality in regards to hammering as the wider surface reduces the required accuracy. Even during the heaviest stabbing, such as the 2x4 splitting, there was no slipping on the grip, and the stabs were done at maximum force. The only real downside is that the guards/talons are a bit square around the corners and thus can cause some discomfort under high pressure contacts. This can be addressed by filing or grinding to round the square edges which make it a lot more comfortable in partial grips.

Sheath

The knife came with an Airborne Deluxe Knife Sheath made from ballistic nylon by Blackhawk Industries with a Kydex liner, it weighs 140 grams. The nylon offers some shock absorption to the kydex which can have problems with fracture at low temperatures. Cordura does however gives up some abrasion and cut resistance when switching from Kydex, and as well as a lower tolerance to open flame. The stiches can also fray, wear or simply get cut. So regular maintenance checks are in order.

There are a number of differences between the the Blackhawk and Special Operations Equipment sheaths as seen on the WB's. The liner that Blackhawk uses is glued in place making removal for cleaning or repair difficult. The SOE liner is just tied in place through cord laced though a drainage hole in the bottom of the liner. SOE also has a soft liner inside the Kydex which reduces the noise of the draw. Finally, SOE individually fits the sheaths to the blades (on a per model basis), the Blackhawk sheath is a more universal product and thus the TAC-11 does rattle a little in the sheath.

The Blackhawk sheath comes with a piece of cord with a leg strap which is held nicely in place at the top on the back if not used. The retention strap is also adjustable and completely removable which allows the user to chose ease of draw over higher blade retention. Lastly the pouch on the Blackhawk is sealed with an adjustable, and removable, Velcro strap, while the SOE has an adjustable plastic buckle. The Velcro is more durable and lower profile, but the buckle is quieter and much more difficult to foul up with mud/grime. The amount of force needed to tear the Velcro pouch strap off could be encountered if snagged on a branch while running, which could cause the loss of the contents of the pouch, of course some epoxy could make the attachment permanent.

Both have as features a break-away belt loop (Velcro) and a large amount of rigging options. Both offer a conversion from high-ride to low-ride. SOE does this by allowing the belt loop to fold down and snap into the middle of the back. With the Blackhawk version a similar procedure is used however a couple of Velcro connections are used and it is a more rugged design. Both sheaths were also inspected by a seamstress who pointed out several differences :

In short the Blackhawk had a "cleaner" design, while the SOE was much more reinforced.

Steel Choice

One of the advantages of a steel that has an inherent high impact toughness is that you can run it very hard and it still will be able to resist fracture from hard contacts. The high hardness will give you greater strength and as well more compression resistance. This means that overall the knife will be far more durable than another knife made out of a steel that has to be made softer to get the necessary impact toughness. For example, the TAC-11 was used to clean up lots of old scrap and assemble some makeshift furniture. The tip was used to split apart boards to get the required nails, and the pommel was used as a hammer to assemble a stool and table. The spine of the blade was also used to bend some nails out of the way for safety reasons. Because of the high hardness the blade was not indented by the nail contacts, and because of the high toughness it did not fracture. After a cleaning to remove the rust and other debris from the contacts (the rust was off the nails not the knife blade) you could not tell the blade had been used.

Comments and references

Comments can be sent to : cliffstamp[REMOVE]@cutleryscience.com or by posting in the following thread :

Tom Johanning also has a website : http://www.survivalknives.com/ you can visit for more information. You should also check out the following reviews by Dan Kohlstrom :

There is also a website for Blackhawk Industries, they offer much more than just quality knife sheaths and are worth checking out.


Last updated : 01 : 10 : 2006
Originally written: Tue Nov 19 20:06:41 NST 2002
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