Re: Polishing Lexan or Plexiglass

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Polishing edges to get that glassy clear look:

1) Make sure it's reasonably smooth.. sandpaper on a block or a fine file,
or a belt sander
2) scrape the edge with a razor blade.  the sharp edge of the blade should
be at right angles to the direction of scrape (along the edge), and the
blade should be almost at right angles to the surface being scraped.  When
you are done, the edge should have a "frosted" or translucent appearance
that is quite uniform. (It's very different from the sanded look).  If you
stick your greasy thumb on it, you should clearly see the fingerprint.
3) Carefully! fire polish it with a propane torch .  This takes a bit of
practice to get the distance of the torch right and the time of heating
right, but if you've got the scraped surface, it takes a second or two for
the frosted surface to melt and go perfectly clear.  I've found that you
want to keep the flame several inches away, so it's just the hot combustion
gases hitting the plastic.  Keep the torch moving!
4) If you need more polish than that, you can get plastic polish (which is a
very fine abrasive much like jeweler's rouge...) and go to town.  Aircraft
supply places carry it to polish aircraft windshields and windows, where
you're always trying to get rid of those horrible scratch marks that make it
hard to see when you're flying into the sun.

This is definitely something where a few hours of practice is needed.  Hie
thee on down to the plastic scrap bin and get scraps of a)the same kind of
plastic! and b) the same thickness of slab.  You'll need a whole package of
single edge razor blades too.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, April 08, 2003 7:27 PM
Subject: Polishing Lexan or Plexiglass


 > Original poster: "Mark Broker by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<mbroker-at-thegeekgroup-dot-org>
 >
 > After much thinking and internal debate, I decided to make my next TC
 > primary base out of 1/2" thick Lexan and the primary winding supports out
 > of 1/4" lexan.  The base will be 18" in diameter, there will be 6 radial
 > supports for the primary winding (about 13 turns of 3/16" copper tubing).
 > (3.5"x 18" secondary with 28AWG, 12/60 input, sync triggered gap, GeekCap,
 > FWIW)  I'm wondering if there is any way to polish the edges to
 > reduce/remove machining marks from the Lexan.  I have only attempted fire
 > polishing with a blow torch once, and the results were abysmal. :/
 >
 > Thanks,
 >
 > Mark Broker
 > Chief Engineer, The Geek Group
 >
 >
 >