I recall looking at many, many listings as well.
Tapecase 423-3 UHMW tape, 3 mil UHMW, 2 mil adhesive (as far as I have been able to determine)
I started thinking about Teflon but it flows under pressure, so no good.
A CN post suggested UHMW polyethelene.
Complicating matters was the way the descriptions are structured, as the tape is so thin, the adhesive backer starts to make up a significant percentage of the overall thickness!
I eventually used the 3M data pages for information on what was available, and how thick the backers and UHMW portion could be expected to be. Adhesive backers run 2-3 mils IIRC. The thinnest 3M product, 5421, was about 7 mils overall. Too thick, as it turned out.
I ended up not trying the 3M tapes due to cost and unfriendly form factors, and they would not have worked anyway.
I looked for well reviewed tapes with specifications, and the Tapecase products fit. The sidebar mentions nylon, but they are UHMW PE tapes.
Note that the product numbers are similar to the 3M products but are definitely different, the final digit on the Tapcase, but not the 3M, relates to the UHMW layer thickness.
From my purchase history, I bought the 5 mil overall, 423-3, 3 mil UHMW + 2 mil adhesive backer,
I first tried the Tapecase 423-5 tape but it was too thick. Amazing the difference .002" can make.
I have 'slicked' 2 Vixen focusers (apparently pulled for upgrades) and 3 Syntas. Very, very happy with the improvement!
The upgrade takes under 5 minutes after the first one. You need 3 strips, 2 for aluminum and 1 for the mystery plastic at the top (particularly important on the Synta, the factory plastic is nearly useless). I trimmed them to exactly match the width of the rails.
I cleaned the rails of all grease with acetone and/or lacquer thinner (HD, Lowes, or paint store metal can type), throughly.
I have not needed any lube or graphite, this stuff is slick!
The adhesive backer has adhered well, no shifting seen.
Expect to experiment.
You may take a couple of tries to get the correct lengths for the rails, and gluing them straight on a single try. I did not try to restick anything. IIRC I ran the tape nearly to the ep end of the rails, and slightly past the objective end, folding and sticking the excess on the rail end. No issues so far on that. It was a juggle to align the tape with the rail given my giant fingers, but I think a tweezers helped, as did starting at the ep end and making the final stick at the objective end, with extra tape to hold onto, trimmed when finished.
Be sure to loosen all the setscrews as you will need the clearance to reinstall the focuser tube. After some experimentation you will figure out the appropriate torque for the setscrews when done. I found that my final adjustment was always for the top two, near the focus lock screw.
I keep using this tape, and the thicker 423-5 for a wide range of uses, scope and non-scope. Which reminds me, I have to add a strip to restore smooth unfolding to my convertible top on the car.
I have not had to re-do any focusers, but at less than 10 minutes for the procedure, not an issue.
Edited by markb, 11 October 2019 - 07:48 AM.