ORIGINAL: Cougar-RCU
Now to just find that tube someplace ! haha
Aerospace Composite Products is one good source. The .156" x .118" size fits the 4-40 nicely. They also have the .120" x .078" which fits the 2-56. Jeff's method is my method too...I've done that for many years on Pattern planes. I also use the tail of the thread to wrap the carbon tubing end and ca the thread in place. That's to keep any potential split from happening. I have also used aluminum tube over the end of the carbon and that work well too