In the related photo, you can see all of the layers and parts fully disassembled, including the internal structure of the knife: damascus blade, titanium tang wrap/handle core, two titanium liners, and the front-top and bottom bolsters with their under-liners.
At this juncture, it’s a good idea to carefully de-bur the bolster holes in all layers, as well as to give all parts a light, flat rub on 320-grit sandpaper. The sandpaper will ensure that dirt and other particles are removed, and that the parts are clean before reassembly. The next step is to tap (thread) the two bolster holes drilled thus far in all layers of the knife.
Use a 2-56 hand tap to thread the previously drilled holes. Tapping involves patience, above all things, and in order to cut threads into the sides of drilled holes, taps have to be extremely hard. As such, they are brittle and prone to breakage. Use new, sharp taps with cutting fluid.
The Tip of the Tap
Carefully and constantly check for straightness. Gently insert the tip of the tap into the hole, and with a little pressure, give it a clockwise twist to get it started. This is the only time you should use pressure. Once you feel it bite, let the tap do the rest of the work. Using small one-eighth and one-quarter turns, twist the tap further into the hole, back it out, then repeat just a little past where it reached the first time.
You will be able to feel when you are biting into fresh material. If you hear a loud squeak, immediately stop and reverse the tap! It’s better to take a half an hour per hole, if necessary going through several taps per hole, rather than break a tap, especially in titanium.
Use a fresh tap per bolster, particularly when tapping titanium. It may even take two taps per bolster. It has taken me up to eight hours to remove a broken tap. It’s not fun! I have recently discovered that an EDM shop close to my house can effectively blast out broken taps for about $60 a pop.
After all the bolster screw holes have been tapped in all parts, de-bur once again. Reassemble the blade, tang wrap/ handle core and liners, and again run a 2-56 tap through the holes to blend the threads. Disassemble, de-bur and reassemble.