Gooey rollers again.

[Allison]

>
>Subject: Re: Gooey rollers again.
>   From: ard at p850ug1.demon.co.uk (Tony Duell)
>   Date: Wed, 22 Aug 2007 22:23:07 +0100 (BST)
>     To: cctalk at classiccmp.org
>
>> 
>> I picked up a nice Decision Data model 8010 keypunch machine through 
>> govliquidation.
>> It looks to be in good shape EXCEPT some rollers have turned to goo. 
>> They act just
>> like peanut butter, looks like it too. These are not simple round 
>> rollers but are tapered,
>> and there are 16 of them in a complex arrangement. Any ideas on how to 
>> fix them?
>> I guess I'm going to have to find some suitable plastic and turn them on 
>> a lathe. Probably
>> beyond my ability.
>
>Turning flixible materials is not easy, the darn stuff tends to distort 
>and not end up the size or shape you expect.

Actually is fairly easy once you know how.  You need a lathe and a rotary 
grinder with the right wheel (correct abrasive).  Rather than using the 
usual tool (cutting edge) you apply the grinder mounted on the cross peice
so than you abrade away the urethane, silicone rubber or whatever flexible 
material is used.  The process is slow but with care you get excellent 
results.  Learned than from a machinest that was really good.

The real trick is getting basic materials to make said rollers even if 
they are the wrong length and shape but larger.


Allison



>
>I've heard that cooling it to dry ice temperature helps. Liquid nitrogen 
>is too cold, the stuff then behaves like glass and just shatters.
>
>
>Another posibility would be to make a mould and cast new parts using one 
>of the 2-part synthetic elastomers. The name 'Devcon' seems to ring a 
>bell for this, maybe a google search will find something. There's a book 
>entitled something like 'How to cast small metal and rubber parts' that 
>covers this, it's aimed at the classic car restoration gugs, but the 
>principles should be the same :-)
>
>-tony