Just a quick inexpensive way to do it. I used the arrow shaft size carbon fiber tube.Then I used 11/2" allen head 4/40 bolts and ground down the heads so they fit inside the tube. (You could use all thread but the bolts are stronger) Then thread the bolt on 4/40 blind nuts as caps. The flanged end fit inside the tube to center the bolt.(Not all brands of blind nut will fit inside so check it first).Stuff paper down inside the tube to hold the glue. Use epoxy or JB Weld to glue them on. The blind nut edge can be ground to match the tube O. D.