Restoring Nylon parts (like the card guides in a PDP-8a chassis)

[Paul Koning]

> On Mar 21, 2016, at 1:02 PM, Doug Ingraham <dpi at dustyoldcomputers.com> wrote:
> 
> A friend mentioned that there was a thread about the card guides in an 8a
> or 8e chassis but I was unable to locate it so I am posting this as a new
> thread as it has more relevance than just specifically those card guides.
> 
> Nylon is hygroscopic. Hygroscopic means it has the ability to absorbs
> water.  As nylon ages it drys out.  When nylon dries out it shrinks and it
> becomes brittle.  If a nylon part has not yet cracked or been damaged by UV
> it can be restored to almost like new simply by boiling it in water for 15
> to 20 minutes.  Boiling will force water back into the material and it will
> expand and soften.

Neat.

> ...
> Unfortunately there are no adhesives that will adhere to nylon long term so
> it is not possible to repair broken nylon parts in a usable manner.  

True.  But can you weld it (with a heat gun and nylon filler -- the way is routinely done with polyethylene)?

> Nylon
> while cheap and easy to injection mold was probably not the best choice for
> card guides.  But then who would ever have expected these machines to still
> be coveted 40 years after manufacture.

One possible consideration (apart from cheap and easy to manufacture) is that nylon is self-lubricating, a useful property for guides that have sliding contact with the card.

Some 3d printers (not the very cheapest but still moderately priced ones) will handle nylon.

	paul