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Joined: Jan 2005
I've done about 10 card reader repairs trying various materials (o-rings, rubber feet, tubing). I've made all of these work, but by far the best one and the one probably closest to the original that I've found is silicone rubber tubing 1/4" OD x 1/8" ID. It fits on the gear shaft perfectly without the need to glue it on and provides plenty of contact area with the card (unlike the o-rings).
This is readily available from Small Parts Inc. (www.smallparts.com) (800) 220-4242. They sell 10 feet of this (enough to repair 1000 card readers!) for $24 (part # 210005). BTW, they also sell the 1/8" Delrin balls (4 of them) used in the card reader in case you loose them while doing the repair (10 for $2, part # BDLR-2) -- I've never seen these disintegrate, however.
Also, they have .005" beryllium copper sheet (part # BCS-005) that can be used to make card contact springs used inside the reader. (These springs do corrode over time.) And this same material (or the ticker stock BCS-006 or BCS-010)) can also be used to make replacement battery contact springs for the Spice series calculators. (Just cut to size, shape it like the original contact, drill a 1/16" hole in it, drill out the rivet holding the broken contact and secure the new contact with an 0-80 screw and nut. Takes about 5 minutes and looks and works great!)