Customizing Zero Tolerance 0551 / 0550

Sometimes, having a limited edition knife just does not "cut it" :-) I have this urge to improve on commercial products and customize them to my own needs and vision.
Zero Tolerance 551 indeed is a fine folding knife, utilizing high-tech materials and manufactured to very high quality standards and precision. If I was to be dropped on a remote island, probably it will be my pocket knife of choice. It has this cool tactical look to it, but when I have an EDC folding knife in my backpack, I would often prefer if it looks a bit more "organic". The G10 black scale installed on the knife is a good choice if you are in the swamp all day long but it is otherwise nothing to write home about from aesthetics point of view. The only thing that really goes for the original scale is the fine surface texture which provides an excellent non-slippery grip - other than that it is pretty boring. G10 seems to be the material of choice for most tactical knives nowadays but there is nothing as "classic" as a knife's "wooden handle".

Here it is my customization attempt for this fine "EL MAX" steel blade by Zero Tolerance (btw. my s/n 1560 knife is one of the last manufactured units in the limited Model 0551 run - less than 1600 pieces were produced according to KAI USA Ltd.)

ZT Model 0551 original, brick pattern G10 scale (bottom).
For my custom scale I decided to go with Desert Ironwood (Olneya Tesota). In my first attempt, I made a scale with exactly the same thickness as the original G10 scale  (~3mm). It was a good learning experience (middle of the picture). The scale came out nice but I felt that I could do better. I realized, that I can add some thickness to the scale and improve the hand grip that way. It was going to give me ability to modify more aggressively the surface relief. My final version is approximately 5 mm thick (top)

Desert Ironwood has absolutely beautiful colors and grain pattern. It is also a very, very hard and dense wood - in fact it is so dense, it wouldn't float. While it looks amazing and IMHO is one of the best choices for knife handles, it is VERY hard to cut and work with. I used a very thin Japanese Pull Saw to slice the wooden block into slabs for the scales. The original block was only 3/8" thick so I had to fabricate a jig out of aluminum L-profiles to aid the slicing process and get nice even tiles. With the same saw I did the rough cut of the scale and used a set of files to get it to precise shape and size.

One really neat thing about the Desert Ironwood is a unique property of the wood grain. Under a bright light it looks sort of 3D - it has a "depth" to it - the fibers in the grain change color when looked at different angles but at the same time certain areas of the pattern behave differently. This produces kind of a "stereoscopic" effect when the wood is tilted at different viewing angles - much like in the old 3D postcards.

With the added thickness, the knife now looks more "balanced". The grip is much improved as it fills up my hand very nicely. Because of the added thickness, I was able to create indentations in the scale for the index and middle fingers and the handle feels noticeably more ergonomic now.

 Replacing the original stainless steel pocket clip with a titanium clip shaved off some of the added weight (because of the extra thick wooden scale). Ironwood while very dense, is still lighter than the G10 material but almost doubling the thickness increased the overall weight. The total weight of the knife is now at 167 grams - only 5 grams increase from the original. This is not significant at all for practical purposes!
(On a side note - I noticed  that over the 1500 units run, the knife has evolved - the one I have, being one of the latest produced has an extremely small gap between the frame and the lock-bar portion. It is so thin, I suspect it is a laser cut. On older knives, the gap is much wider and on the first few hundred ones there is also a small manufacturing hole in the corner of the lock-bar.)

 After making the rough cut from the Ironwood slab (with the direction of the grain pattern in mind) , I drilled all of the holes, sinking the screw heads, while  leaving the original thickness of material under each screw. The pivot screw hole should be done with an extreme precision and the thickness of material between the screw head and the steel liner must be identical to the original scale. This is absolutely crucial in order to provide the proper tension for the pivot point and center the blade between the frame and the liner. After I did the holes, I shaped the scale to the precise contour of the steel liner using files. Then I made the indentations for the fingers in the surface and finally beveled the outside edge of the scale.

 Here it is the final result! After finishing the surface, starting with a wooden file and then sandpaper, going all the way down to 1200 grit for an extremely smooth and polished look, I treated the scale with Tung Oil Finish. It took a few applications but it was well worth it. Tung Oil is great for this as it soaks deep into the wood grain, giving it protection while bringing out the natural grain pattern and colors in a nice satin finish.

I absolutely love the way it looks - it really warms up the "super-steel" EL MAX blade with a nice "earthy" patterns and colors - just a "classic" knife look for a folder!

And if you flip it - it is all space-age steel and titanium for the high-tech look I like to see sometimes.

btw. I did not use ANY power tools - everything, including the drilling was done by hand. All in all - about 10 hours worth of work per scale.

I was not using the lanyard hole and was wondering what it can be used for, besides the obvious purpose. As a person whose childhood fascination for "glow in the dark" stuff never went away, it was not very difficult for me to come up with an idea. I mixed some glow-in-the-dark pigment (Strontium Aluminate doped with Europium, SrAl₂O₄:Eu) with clear silicone sealant and injected the mixture into vinyl tubing - 1/4" OD and the "fireworm" was born (sorry, If I took the name of an already existing product). I prepared two different mixtures, using green and aqua color pigment. After the silicone cured, I cut a piece of about 14 mm and inserted the "fireworm" tubing into the lanyard hole. The 1/4" OD vinyl tubing is a perfect compression fit - actually, it took some effort to insert it all the way through and now it will not go anywhere. It can be removed if pushed out with a tool (the back side of a 1/4" or a tad smaller drill bit will fork fine)

The tubing goes through the scale, the steel liner and the titanium frame on the other side. All materials used are 100% weather resistant and there is no danger for damage by the elements whatsoever. It will not yellow or harden.
IMHO it is a pretty elegant solution as there are no permanent alterations to the knife and the GID (glow-in-the-dark) insert can be completely removed, restoring the knife to the original stock version.
btw. the two holes on the front scale (for the pocket clip) can be still used to attach a small lanyard loop or a small titanium plate with lanyard hole in it. I might even create a notch on the back of the scale so the plate is "pinched" between the scale and the steel liner, leaving the scale's top surface clean.

The Europim activated Strontium Aluminate is the "good stuff". This pigment (also called Super-LumiNova) is available mostly in green and aqua colors (green being the brightest glowing) and after charging with light it will glow for hours and hours. This is not your grandfather's Copper activated Zinc Sulfide which will go dark in less than an hour after exposure. Completely charged Strontium Aluminate can glow for up to 8-12 hours. It is charged primarily by the light's UV component. I experimented with two different particle sizes (large crystals of green and fine aqua powder). The large particles will glow brighter but one can differentiate the actual particles in the silicone medium. The fine particles create more diffused and even look. I was careful not to "overload" the silicone medium with pigment - if there is too much pigment in the mixture, it will become opaque and will glow only where it is exposed to the charging light. By leaving the mixture semi-transparent, I ensure that light penetrates through the material and charges pigment particles deep inside the silicone medium. If too little of the pigment is added, the light output will be decreased so the right ratio needs to be found. The idea is for the "fireworm" glow tubing to be charged entirely (or at least close to), even if only partially exposed.

 After charging the glow-tube with light, the knife can be found in a complete darkness for hours. The light is visible from 5 out of the 6 sides.
I ordered some tritium filled tubes (GTLS) to experiment with and I might even try to create a hybrid solution - a combination of Phosphorescence / Radioluminescence like in a Prometheus Watch.
It will be a useful for other objects used in the darkness - flashlights, key-chains, map lights, tools, etc