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On Wed, 4 Feb 2009 12:44:31 -0800 (PST), wrote:

On Jan 31, 9:35*am, "Garland Gray" wrote:
I need to replace some old plastic sheaves, and I have the option of sheaves
made of Delrin, acetal, or glass filled nylon. (I have learned that delrin
is acetal, *but don't know if all acetal sheaves are delrin).
So what are the relative attributes of acetal and glass filled nylon
sheaves? I read somewhere that GFN might be more abrasive on the pin, but I
assume that it is stronger. Ronstan sells both, but their website doesn't
solicit questions.

Nylon is very susceptible to UV degradation, but low friction. Don't
use it unless the part is both shielded from sunlight, and gets a lot
of running wear. Acetal is somewhat harder, better at resisting UV,
slightly higher friction, costs more.

It seems likely to me that a drop-in replacement for a specific sheave
will only be available in the material that specific mfg'r choses.

Fresh Breezes- Doug King

It's also important to note that not all nylon is created equal. Nylon
not made specifically for the marine environment may absorb moisture
and swell over time.