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 Post subject: Plastic dial polishing problem
PostPosted: Jan Tue 08, 2019 9:46 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1265
Location: Champaign IL 61822
One of my old radios had an accident: I dropped a Kleenex saturated with toluene
on the clear plastic dial (this radio has the dial facing up). (I was cleaning oil off
a microscope objective).

This glued the Kleened to the dial. I scraped it off, sanded it a bit, and then
used Novus #2 on it. This did not work. I've never had Novus fail before.
The plastic won't bedome clear, and won't shine.

Is this common? Is there a cure? I suppose I could post a picture.


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 Post subject: Re: Plastic dial polishing problem
PostPosted: Jan Thu 10, 2019 1:57 pm 
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Joined: Feb Thu 08, 2007 2:23 am
Posts: 986
Location: central Ohio 43062
What you are going to have to do is sand out the distortion provided its not too deep in the plastic.You can buy a clear plastic polishing kit off fleabay.It will have several grits of sandpaper,the finest at 12,000 grit.You start with 400 and go through each grit and then use a micro polish.MicroMesh is the name brand kit.Works very well.


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 Post subject: Re: Plastic dial polishing problem
PostPosted: Jan Thu 10, 2019 3:57 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1895
Location: Monroe, NC 28112 USA
I'm sure that kit will do a good job. But an auto parts store just a few blocks away has a $10 Turtle Wax Lens Restorer kit.. 4 different grit sanding pads, sanding fluid, buffing compound and... towelettes of top coating (I don't use.) Did a great job on the acrylic safety mask on a 1949 Admiral TV that had been smeared with paint stripper. Fortunately the mask is thick enough to survive sanding 10 to 20 thousandths down...

From your description however I suspect that the toluene may have penetrated into micro fissures so that you may never get down to really clear material... :(

Robert


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 Post subject: Re: Plastic dial polishing problem
PostPosted: Jan Thu 10, 2019 4:24 pm 
Member

Joined: Feb Thu 08, 2007 2:23 am
Posts: 986
Location: central Ohio 43062
Polishing a headlight is much different than fixing deep scratches and imperfections. You need to step sand clear plastic to get a optically perfect part. You need more than 4 grits. I have done this many times and know firsthand how it is done. If you want it right get the micro-mesh.


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 Post subject: Re: Plastic dial polishing problem
PostPosted: Jan Sat 12, 2019 4:18 am 
Member

Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1265
Location: Champaign IL 61822
It was not "deep scratches and imperfections". It turns out it was deep however.
When I first tried to fix it, I suspected that there was still toluene in the plastic,
making it soft. So after waiting two weeks I tried again, using first 220, then 400 then
800 sandpaper, dry, then Novus #2 wet, then Novus#2 dry. It was clear that the
#220 sandpaper was sanding through a many thousandths of an inch hazy layer.
All of a sudden it got sanded looking rather than hazy. Then the finer sandpaper
made that finer and Novus polished it. It now is clear enough to see all the
dial markings clearly, and see the pointer, which was previously invisible.

I'd call it a poor quality polish, but it will do to make the radio usable. I've gotten a
mirror like finish on the outer crust of Bakelite, this is much worse, but
better than the dull inner regions of Bakelite.


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 Post subject: Re: Plastic dial polishing problem
PostPosted: Jan Sun 13, 2019 4:01 pm 
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Joined: Jun Sun 16, 2013 10:12 pm
Posts: 776
Location: Brandon, SD
What kind of radio is it? Could a replacement or reproduction be found? Seems like replacing it would be a more time and cost effective solution... Does www.dialcover.com have what you need? I have bought some of Marks reproduction dial covers and they are fantastic in fit and function...


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 Post subject: Re: Plastic dial polishing problem
PostPosted: Jan Sun 13, 2019 4:32 pm 
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Joined: Feb Thu 08, 2007 2:23 am
Posts: 986
Location: central Ohio 43062
I agree, sometimes it's better to go with a new one if available .Mark can one if he has dimensions to make the mold.


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 Post subject: Re: Plastic dial polishing problem
PostPosted: Jan Mon 14, 2019 4:12 am 
Member

Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1265
Location: Champaign IL 61822
Its a Philco G978. The problem is that the numbers are silk screened on the back of the
plastic dial. A new one would require having decals made up. Glass could
be used instead of plastic. Its 14 x 3.5 inches.

This is not a vintage fancy case. Its an extremely blah case utilitarian
1958 AM - FM, though wood. Its a very good performer on FM, receiving
HD radio stations very well, even one with an SCA subcarrier. That's why I like it.
I got it free.

It has one unusual feature: the dial and knobs are on top, the
whole front is occupied by the speaker grille.


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 Post subject: Re: Plastic dial polishing problem
PostPosted: Jan Mon 14, 2019 5:12 am 
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Joined: Jan Tue 31, 2012 1:55 am
Posts: 8826
Location: Mountains of Mourne. Ireland.
It takes roughly seven seconds for any liquid or solvent to penetrate the skin.
In about 30 seconds it can be traced to all major organs in the body.

Since 2005 my gubament has banned the general sale of products consisting of greater than 0.5% toluene.


A large part of my life involved working with industrial adhesives and all sorts of nasty chemicals.

Believe me - failure to take the correct precautions - gloves - respirator - eye protection and working in a well ventilated place... this will catch up with you in the end.

Greg.


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