Hello Amy
The point of putting the blade in the plastic tube was that you could throw it, (I know very wrong) into your tool box and go off to another section of the works. We cut the cap with a nearly new blade not a fine blade. For fine blades we put a bit of foam in the bottom of the tube to stop the blade hitting the sides of the tube. We used foam blocks on the bench. These came as packing for electronic components and were glued to the insides of the cardboard boxes. The foam does fall apart over time, but as its free that does not matter. The only problem was when working in a clean room,but this is ship building so no problem.
All the best Ken.