I got a scrap titanium rod with a canal and two transverse holes. God knows what it used to be. But I am pretty affirmative that it must be titanium. I can tell this from the anodizing color reaction（i ran a test） and its unique luster!
This titanium rod had a tapered end and looked exactly like a pen. More coincidentally, the gel-ink pen refill filled just right and tight into the canal of this rod. After confriming its titanium composition, I conceived to make in into a pen， a tactical one which can break glasses in case of emergency.
Step 1: Fixing the Hard Alloy Tip
I just can't understand howcome there are so many "tactical pens" which claimed to be able to break glass or windshield but is made of weak and soft materials like aluminum.
To break tempered glass windshield , hard matals is essential.
I found several tungsten carbide cones to serve this purpose.These little cones are originally used in the lather as a core clamper. They are hard enough to scratch glass and in the mean time strong enough to withstand necessary hit.
Now that the ideal material arrived, I enlarged the canal a little bit then hammered it into the canal with a piece of wood. The cone would not go further in longitudinaly cuz I enlarged the canal with a limited depth. Neither would it move side to side nor even drop cus i ground the canal carefully to make them fit just well.
Step 2: The Tip Holder
The original rod had a tapered end but the taper just ended halfway.
To make it like a pen, we need to make a tip continuous with the taper curve of the rod, and it must be hollow to hold the refill. I name this little stuff "tip holder".
The tip holder was made out of a TC4 rod. This is the most painstaking procedure, for I have no access to a lather delicate enough to process such a little piece. Except for drilling the canal， I have to do it with vise and files.
I didn't do any screw thread， friction hold this little tip very well to the rod.
Finally the pen is assembled.(Sorry for the ugly refill, i just made it leak by hitting the bottom against some stuff )
Before that I added a clip to it to make it more like a pen.
Yes u are right, I didn't find a decent cap for it . Pls do let me know if u have any idea about the cap.
Actually, the hard alloy bottom is more useful in marking the metal pieces, which is 50/50 purpose of the design.
Thanks for viewing.
I'd really appreciate it if you can provide any suggestions!