The materials for collimating focussers...
The clear tape is easily had locally. The aluminium tape can be had locally as well, although not as easily, and from heating & air supply-stores.
Although, I had to order the PTFE, as it's a bit more exotic, and I got my own from ePlastics in California...
It was rather economical, for 12" x 12" sheets, in thicknesses of 0.005", 0.010", 0.015", and 0.020". Thus far, I've only used the two thickest in this madness.
The aluminium tape acts as a base for the PTFE. One, two, three, or more layers, each on top of the other, can build up the original substrate to the thickness required. Examples of past projects...
The method works especially well with focussers of metal, like a proverbial charm...
Most well-collimated those two were, afterwards.
The layering of the bearings...
