They are cast in acrylic, these same basic steps could be used to make a snakeskin, candywrapper, photo blanks, etc too.
1) cut swatch of the carbon fiber fabric to exactly fit around the tube. I've seen various recommendations on things like cutting at an angle or cutting a wedge shape in the ends so that as they come together the seam "moves", thus hiding it better.
2) glue the swatch to the tube. Epoxy seems to be the prevailing choice here.
3) fill the tube with BBs, lead weight or anything so that it won't float later due to trapped air.
4) seal the ends of the tube. Clay, Playdoh, potatoes, I've seen all suggested. One that looks very slick is small corks glued to little squares or circle of wood so that when plugged, the bits of wood act like spacers and keep the tubes from touching bottom or each other. The major diameter of the spacer would be on the order of 3/4" to 7/8"
5) place tube(s) into a mold, the mold could be just a shallow tupperware container although you can purchase special molds for working with PR
that will release. Just big enough to hold your blanks, not touching and deep enough to allow the PR
6) pour in the clear PR
(poly-resin) or Alumalite. In the case of PR
, add the drops of accelerator based on the volume of material and thickness of the finished slab. Instructions are on the bottles.
7) Knock it on the table a few times to remove the bubbles.
8) Place in a chamber that you can both place under vacuum and pressurize. Only need a little vacuum but the general consensus for the pressure seems to be around 40 to 60 PSI. The common choice is a paint pot from Harbor Freight. The idea is that with a little vacuum for 1/2 hour or so and then switching to pressure gets all the itty-bitty bubbles out and you get a glass clear casting. Note - other reports suggest this step is not 100% necessary.
9) Wait for casting to harden. YMMV
10) Cut apart into sticks with bandsaw. Caps on the end can be removed by cutting right at the end of the brass then knocking the plug out of the tube. Watch how the BBs scatter all over the floor...
11) Give tube to Harry to turn on his metal lathe.
Alternate method -
buy them from somebody already made...