Estes Little Joe II (Small) Build, Part 4, DIY Centering Rings

You can't simply order 5/58 centering rings from Balsa Machining Service. I'll have to cut these out from mat board, about .050" thick

With a thin mechanical pencil, trace around a BT-5 and the BT-58 tube. Be sure the BT-5 is well centered inside the BT-588 circle. It might take a few tries to get it right.

The mechanical pencil traces a line to the outside of the body tube diameter.
Cut out the center hole first, it's easier to do when you have more of the board to hang onto. Cut just inside the pencil line.

Normally I use a break off blade knife for most cutting. On something this tight I'll use a new #11 blade.

Wrap some sandpaper around an engine casing to sand and round out the inside circles. Sand a bit and check the fit of a BT-5 tube until you get a good friction fit.