I recently got a Commodore SX-64 to play with. Problem; the floppy drive, a Commodore 1541 was working a bit too randomly to my taste. Luckily, it is quite to find good advice (but also bad one) on the vast internet.
It came out to be a problem with the drive spindle clamp mechanism. I found a very useful forum post that I'll replicate it for convenience:
The design of them is that a plastic cone expands a split clamp that grips the disk from inside, whilst pressing it against the aluminium seat underneath. A spindle runs through the plastic clamp and cone, and a spring sandwiched between 2 thin metal washers. A metal brace pushes the whole assembly together, and is held by the front drive latch. A metal washer above this brace isolates a circlip, which holds the spindle against spring tension.
The design flaw is that the spindle binds to the plastic cone, causing a rotation moment between the spring and it's isolating washers. The grinding noise you here is the spring end chewing through one or both of the washers.
To fix the problem you must do the following procedure:
1: with the drive LATCHED, remove the circlip. 2: remove the 4 front screws holding the front fascia of the drive and spring it forwards (mind the LED cable!) This will allow you to lift the brace, and to drop the shaft enough to remove the assembly. You'll find the black grease has gone sticky/hard. 3: clean everything, including the spring and chewed out washers. 4: reassemble, but reverse the washers so they present a non-scored surface to the spring. Apply a SMALL amount of nylon grease, but **ONLY** to the bronze bearing in the plastic cone, and the spring in the middle - NOWHERE ELSE. Replace the washer at the top, and refit the circlip. 5: Reassemble the drive.
Do not use any mineral-based oil - it will creep, and get onto the clamping surfaces. Do not put it anywhere else than where I have proscribed - the wrong surfaces will slide together and the problem will recur.
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