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From: Michael Salem on 19 Sep 2005 13:15
Steve H wrote about repairing scratched CDs, starting:

> There are a couple of types of buffing wheel ( or mops ) widely
> available.

I copied his posting into another newsgroup interested in the topic, and
had an interesting reply from someone who know about polishing, but
hasn't tried it on CDs.

I wrote there:

>There's an interesting thread on cleaning CDs which I'll quote in case
>anyone's interested.
<test quoted from this thread>

Response:

I've been tempted but have no disks that couldn't be read with the
'repair' stuff I've got.

I would certainly have gone the routes suggested but:

1) Melting the plastic would have worried me, I would therefore have
taken the water-based abrasive route. That pretty well means a somewhat
slower buffer and a squeegee bottle full of water.

2) Holding things like these disks against a fast-rotating buffer is
potentially hazardous. Either abraded/burned (friction is significant)
fingers or the reception of the disk into the face/gut at high speed are
significant risks.

3) I would be inclined to a wet drill-based 'lambswool' buffer, with the
disc nailed to a bench. It may be that no actual abrasives are needed.

4) NB Its the devil of a job producing scratch-free mirror surfaces.
Extreme cleanliness is required as you move up the grades. Certainly
once a buffer has been used for one grade it can NEVER be used for a
finer grade ever again.

Best wishes
--
Michael Salem (not the actual author of the detailed comments)
From: Bill Turner on 19 Sep 2005 17:08
Michael Salem wrote:

> 2) Holding things like these disks against a fast-rotating buffer is
> potentially hazardous. Either abraded/burned (friction is significant)
> fingers or the reception of the disk into the face/gut at high speed
> are significant risks.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

1. I've done dozens if not hundreds of disks and never burned/melted
one. The plastic in a CD or DVD is quite resistant to melting.

2. I have the buffing wheel rotating such that if it 'grabs' the disk,
and it sometimes does, it flings it away from me, not toward me. Common
sense, guys. And I always wear safety goggles. We're talking light
pieces of plastic with no sharp edges here, not large chunks of metal.

Mr Bill
From: Steve H on 20 Sep 2005 03:25
On Mon, 19 Sep 2005 18:15:57 +0100, Michael Salem <a$-b$1(a)ms3.org.uk>
wrote:

>Steve H wrote about repairing scratched CDs, starting:
>
>> There are a couple of types of buffing wheel ( or mops ) widely
>> available.
>
>I copied his posting into another newsgroup interested in the topic, and
>had an interesting reply from someone who know about polishing, but
>hasn't tried it on CDs.
>
>I wrote there:
>
>>There's an interesting thread on cleaning CDs which I'll quote in case
>>anyone's interested.
><test quoted from this thread>
>
>Response:
>
>I've been tempted but have no disks that couldn't be read with the
>'repair' stuff I've got.
>
>I would certainly have gone the routes suggested but:
>
>1) Melting the plastic would have worried me, I would therefore have
>taken the water-based abrasive route. That pretty well means a somewhat
>slower buffer and a squeegee bottle full of water.

You'd have to go some to melt the plastic. I wouldn't even have
mentioned it save for the fact that people might be inclined to really
'work' on a deep scratch. My industrial mop runs at something like
15,000 rpm, with 1/2 horsepower - and even with a 6" mop I've never
melted a disc...though I could if I wanted to!
I would say that the biggest risk of damage comes from the temptation
to flex the disc against the wheel.
>
>2) Holding things like these disks against a fast-rotating buffer is
>potentially hazardous. Either abraded/burned (friction is significant)
>fingers or the reception of the disk into the face/gut at high speed are
>significant risks.

That's why I noted the working position - at around the 7 o'clock
mark. In the event of a slip, the work gets thrown down. To run a real
risk of burned fingers you'd need professional kit. A buff on a
domestic power drill might just about warm your fingers.
>
>3) I would be inclined to a wet drill-based 'lambswool' buffer, with the
>disc nailed to a bench. It may be that no actual abrasives are needed.

Wet polishing carries a few risks of its own, most notably the fact
that a wet mop may pick up ( and will hold ) bits of grit. Absolute
cleanliness is required...and plenty of protective clothing ( it's
pretty messy! ). Also, with a static workpiece you have to address the
issue of polishing radially
>
>4) NB Its the devil of a job producing scratch-free mirror surfaces.
>Extreme cleanliness is required as you move up the grades. Certainly
>once a buffer has been used for one grade it can NEVER be used for a
>finer grade ever again.

This is pretty much true, but in practice I've not found it necessary
to reproduce a mirror finish. It could be done, using a separate wheel
and a finer buffing soap, but I've found the finish left by a
medium/fine soap to be more than adequate.
A 'finishing stroke' ( a light pressure against an unloaded soft mop )
gives, effectively, a finish that's about half a step finer than that
with a loaded mop with the work held against it at normal pressure.

Regards,


--
Steve ( out in the sticks )
Email: anyoldname(*AT*)gmx(*dot*)co(*dot*)uk
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