A shot of the custom RTAK from Chad Engelhardt (the owner) :
The RTAK is on top, the knife on the bottom is a Busse Basic #9.
This a custom RTAK made by Newt Livesay for Chad Engelhardt, with a fourteen inch blade instead of the normal ten. The steel is 1095 with a differential temper, hard edge, spring spine. The blade shows signs of significant use, the coating has just taken on a polished look, no chips or flakes.
The RTAK weighs 780 g and the center of balance 5.2 cm in front of the handle. It has a full flat grind down to an edge was 0.080" thick, and ground at 18 degrees per side. The handle is large, with a significant center swell which is actually kind of pointy and makes for an uncomfortable grip. It is also fairly slick, and lacks an end hook to drive from.
There is a production version of this knife from Ontario which is similar in design and materials.
In terms of raw power, the RTAK had about 65-70% of the chopping ability Wildlife Hatchet when bucking small wood. It was obvious that the performance was significantly lower after just a few sections of wood was cut. It was also significantly behind the Tramontina bolo when limbing. The main reason for the relative low performance was that the edge is far too thick. Similar problems were found when doing wood carving, the RTAK was again readily outcut. Specifically for example pointing one inch tips on basswood dowel, the hatchet could point one in about 15 slices, whereas the RTAK took 37.
A similar knife from Livesay the RCM, had the blade see edge failure while limbing hardwoods. This RTAK handled such work with no problems due significantly in part to the much thicker edge. However During limbing and light brush work on woody vegetation, the handle proved problematic. Best results were with the index and fore finger in front on the swell, but even this placed too much pressure on the index finger. This is further hampered by the grip being a little slick, so more force was necessary to get a decent level of security. A more significant end hook would be nice both to prevent the blade from coming out of hand as well as something to drive from, the latter would only be practical with the swell removed.
Using a belt sander the shoulder of the edge was swept back to 10-12 degrees per side leaving the edge 0.025" thick at the origional angle. The blade was then sharpened using a 1000 and then 4000 grit waterstone and then finished with stropping on CrO loaded leather. It took a fine polish easily which is expected given 1095 will grind readily and has a fine grain. With the new edge profile, the performance increased dramatically. The dowel points increased to 15. The RTAK limbs at the same level as the Tramontina bolo and is more fluid and still stiffer. The edge on the Tramontina is lower in the shoulder by a couple of degrees and the very edge sweep is about 13-15 degrees so its more acute than the RTAK. However the RTAK primary grind compensates and thus allows a more durable edge at the same level of cutting ability.
After a standard limbing session of about 500 chops the RTAK still actually shaved roughly in places and overall was still easily able to cut light grasses, no visible damage except for a couple of preexisting rough spots near the tip left over from the initial finish. The handle of the RTAK took a major jump in comfort once the edge profile was changed to raise the cutting ability, the swell is still too much though. After several multi-hour sessions of limbing (1500-2500 chops) the RTAK was still sharp enough to pop off the ends of boughs, but could not cut grass at all. To sharpen a 1000 grit waterstone was used, producing an edge which would readily slice paper. It was further polished with a 4000 grit waterstone and stropped on CrO to enhance the impact durability, and fine push cutting ability. It can now lightly pop the tops off of grasses with just a wrist flick, and shaves smoothly.
The palm swell was cut off using a Dremel and then a file to smooth out the cuts and increase the radius in some areas. The grip is still a little thin and the filing wasn't perfect, it still needs some work, but there is a major improvement. A solid full grip now has no problems. The handle was also wrapped with guard tape from Lee Valley, a very abrasive self-adhesive tape that gives a very high level of retention. The however tape only lasts a little while with heavy work as it becomes very slick with sweat and wears down. With the modified grip with the tape and the handle was comfortable and secure. The cutting ability was increased for high impact work and fatigue rate lowered, both due to the greater control and comfort. With the modified handle the RTAK grip stood out as superior to the handle on the Tramontina which also became loose, and has ergonomic issues as the fasteners are recessed in the wood which is abrasive. The grip on the RTAK could still be a bit thicker though, with a more pronounced end hook to drive off of. A shot of the modified grip :
As one final modification, the edge was ground flat to the belt sander, producing an edge ground at 12-14 degrees until 0.020" thick and is around 11 degree per side above 0.030". A shot showing the edge profile as received from Chad and the current one :
The latest edge now profile allowed a dowel cut of 11-12 slices, and the bucking ability was compared to the Bolo and through side by side cutting the blades were within a few percent of each other through a few dozen sections of wood being cut. The RTAK also retains a greater edge and overall durability, and more functionality in general due to the stiffer blade, and more ergonomic handle. Corrosion resistance is also higher on the RTAK. The coating is still working despite the very heavy wear. The bolo showed visible evidence of corrosion while the RTAK didn't in the same exposure (rain).
Even with the slimmed down edge profile, the RTAK was undaunted by even the hardest of limbing work, included heavy cutting through dead and seasoned branches, usually done on an angle, however glances are unavoidable on the occasions of heavy ingrowth. However after working with it for four days of limbing, on the last day a final test was done which was to attempt to shear off the hardest seasoned branch stubs. Through three hours the edge held up perfectly. Finally on a very seasoned spruce limb the edge gave way and bent to about ninety degrees. The edge that was bent was still sharp and aligned. The blade was between 0.030" to 0.035" thick behind the bend, and the edge was ground at 10-12 degrees per side in that region, very thin and very acute. This damage can be hammered out with care. Unlike chipping, such dents are also less likely to lead to gross blade failure.
Most machetes are stamped, with no primary grind. A blade like the RTAK which uses a flat grind has the potential of having a advantage in cutting ability, durability and overall versatility for woody brush work. Even if prying ability isn't desired, a higher strength and stiffness makes blades like the RTAK more comfortable to use on harder woods as they don't produce as much vibration as stamped machetes. The only drawback is that the narrow spine on stamped blades can actually be used readily as a limb hammer or sod cutter. The Tramontina for example much more readily cracks off dried branchs as it can "cut" somewhat with the thin spine. Of course for pure light vegetation there is little advantage over a stamped machete aside from the more narrow edge raising ease of sharpening.
Initially the edge profile of the RTAK was too thick for efficient cutting ability and the handle swell was too pointy for a comfortable or secure grip. With the above modifications, the performance increased significantly, and stood near the top of its class. Further improvements would be a more significant end hook to the handle such as found on a axe which would allow a more powerful drive, and to extend the primary grind down further to create a thinner edge. The blade was used for more precise cutting. It can handle such tasks and with the modified edge profile cut well, but generally creates heavy fatigue simply because of the awkward nature of trying to do such work with a large blade. In regards to corrosion, 1095 will patina quickly, but does not tend to pit readily.
The kydex sheath has a hit level of fit and finish. Though it usually wasn't worn when the knife was used as it gets in the way too much. It does make a nice support for a writing pad.
Comments can be sent via email : cliffstamp[REMOVE]@cutleryscience.com or posted to the following thread :
The above thread contains detailed usage commentary from Chad, as well as from Newt on the history and design of the blade as well as its evolution into the Adventure Knife (AK).
| Last updated : | Jun 23 NDT 2004 |
| Originally written: | 04-26-2002 |