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Re: [TCML] Polishing Lexan (small, recessed areas)

I've spent some time talking to the guys at the machine shop here at Pitt and they've mentioned using an air-tight box on which you pull a vacuum and then introduce methylene chloride through an opening. Since this chemical is extremely volatile, it vaporizes and the vapors will produce a similar effect to flame brushing. This will also work for internal surfaces that can't be mechanically polished (threaded bores, etc.. ).

Never tried it, but I hear it works well.. 

Coiling in Pittsburgh
Ben McMillen

----- Original Message ----
From: bunnykiller <bunnikillr@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Wednesday, March 5, 2008 3:54:25 PM
Subject: Re: [TCML] Polishing Lexan (small, recessed areas)

Hey Daniel...

how important is it to maintain the cut "quality" of the pocket?  are 
you going to need a tolerance fit to mate with the pocket or is it going 
to fall under cosmetic appearence?  If it is only a cosmetic value, then 
flame polishing is your best bet to get the surface to go back to a 
clear finish. You will lose the sharp edges from machining the pocket 
but you will get the clear coat as in unmachined lexan. Be careful on 
the time of flame contact, it can invoke surface bubbles on the lexan.

MEK leaves a milky finish as the same as Acetone, which will eventually 
lead to "crazing/alligatoring and yellowing" in months to come. Other 
than that, a labor intensive option is to use a Dremel with a cloth disc 
and a mutiple barage of fine grit pastes to finally get to the clarity 
you need. Altho this system is good, it can be an issue if you have a 
less than delicate touch with the Dremel. gouging and "burning" are the 
main issues with the Dremel....

Re-think your needs and priorities when it comes to machining 
Lexan....   its awesome stuff  but it can be a monster to return to its 
original state after cutting...

Scot D

McCauley, Daniel H wrote:

>Need some expert opinions on polishing lexan.
>Basically, i'm looking to polish small recessed pockets that have been
>machined into blocks of lexan.  For example, a 2"x2" pocket, 0.5" deep.
>Not too keen about flame polishing, especially on a part that will take
>a long time to machine.  Although i have read that MEK solvent is
>something frequently used or a plastic polishing compound such as NOVUS.
>Any thoughts?
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