I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form 'light
pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?


--
https://www.antislavery.org/slavery-...forced-labour/

On Wed, 1 Jul 2020 19:24:46 +0100, Brian Reay wrote:

I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form 'light
pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?

Fine wet-n-dry (going finer as you go, possibly used wet), held over a
very flat surface and the rods held up as a bunch of 4 taped together
if they are very close in length ... or individually if not and rubbed
back and forth whilst rotating slowly till the finish is a good as can
be, then finish with some T-Cut or similar on some cotton / denim,
also held tight over flat surface.

Or if it doesn't matter if the end isn't perfectly flat and you don't
mind a bit of scatter, use a polishing mop and wax on a Dremel,
keeping the speed down.

If it were here I might first put them in the lathe and then put them
on the linisher.

Cheers, T i m

Brian Reay was thinking very hard :
I need to polish the ends of a few (well 4 bits) of short perspex rod, about
3mm in diameter after cutting. The bits of rod are to form 'light pipes' in a
display- each has an LED at one end.

Any ideas how best to polish the ends?

Flatten the ends first, with successively finer wet & dry, then polish
up after the finest with a fine slightly abrasive polish such as
toothpaste, Brasso, chrome polish, or similar.

On 01/07/2020 20:10, T i m wrote:
On Wed, 1 Jul 2020 19:24:46 +0100, Brian Reay wrote:

I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form 'light
pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?

Fine wet-n-dry (going finer as you go, possibly used wet), held over a
very flat surface and the rods held up as a bunch of 4 taped together
if they are very close in length ... or individually if not and rubbed
back and forth whilst rotating slowly till the finish is a good as can
be, then finish with some T-Cut or similar on some cotton / denim,
also held tight over flat surface.

Or if it doesn't matter if the end isn't perfectly flat and you don't
mind a bit of scatter, use a polishing mop and wax on a Dremel,
keeping the speed down.

If it were here I might first put them in the lathe and then put them
on the linisher.

Cheers, T i m

Speed is definitely your enemy when polishing thermoplastics. I've been
trying to polish a bit of "UV haze" out of some plastic headlights
(carefully doing my practice on a bit of dummy plastic at the side, well
out of the beam, just sitting in front of some decorative "chrome").
Even using a polishing mop in my cordless angle grinder at the minimum
speed (which is pretty low), it's easy to melt the surface if you press
a bit too hard.

On 01/07/2020 19:24, Brian Reay wrote:
I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form 'light
pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?



If you have a spare to practice on, I'd sand the end best you can then
wave it in a blowtorch flame.

--
Cheers
Clive

On Wed, 1 Jul 2020 20:50:09 +0100, newshound
wrote:

snip

Or if it doesn't matter if the end isn't perfectly flat and you don't
mind a bit of scatter, use a polishing mop and wax on a Dremel,
keeping the speed down.

If it were here I might first put them in the lathe and then put them
on the linisher.


Speed is definitely your enemy when polishing thermoplastics. I've been
trying to polish a bit of "UV haze" out of some plastic headlights
(carefully doing my practice on a bit of dummy plastic at the side, well
out of the beam, just sitting in front of some decorative "chrome").
Even using a polishing mop in my cordless angle grinder at the minimum
speed (which is pretty low), it's easy to melt the surface if you press
a bit too hard.

I have done quite a bit of cleaning and polishing of 'plastics' (grp /
Perspex / Plexiglas / polycarbonate) and in most cases I've resisted
using any mechanical kit and done it by hand.

I think you can get much more feel and as you say, can make sure you
don't melt anything as you go. ;-)

If something is scratched fairly badly all over you first have to make
it look worse, with say some 1000 grade wet-and-dry (wet). You now
have something free of scratches but opaque. Then you start with the
finer grades till you get to the stuff that feels more like plain
paper. ;-)

Once you are done there, T-Cut and finer cutting compounds to get it
nice and transparent again. ;-)

The only real problem is any protective coatings there may have been.

I have done the above on several motorcycle windscreens, take the
screen off and strip it back to the bare screen, support it suitably
and off you go. ;-)

When done I's have to say that apart from any really deep gouges that
you can really only just smooth out, it looks 100 times better and
with some suitable polish, can generally stay that way for quite some
time.

It's also quite satisfying, if a lot of elbow grease. ;-)

Cheers, T i m

On 01/07/2020 22:15, Clive Arthur wrote:
On 01/07/2020 19:24, Brian Reay wrote:
I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form
'light pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?

If you have a spare to practice on, I'd sand the end best you can then
wave it in a blowtorch flame.

Flame polishing might be the easiest solution if it doesn't have to be
optically flat. Another easy option would be to wet the ends with clear
epoxy and cast it against window glass with a mould release agent.

Polishing acrylic is possible but slow and tedious because it gets warm
and softens when you work it. Expect to use much elbow grease and time.

--
Regards,
Martin Brown

On 01/07/2020 22:19, T i m wrote:

I think you can get much more feel and as you say, can make sure you
don't melt anything as you go. ;-)


Don't they also flame polish perspex but probably there is a skill level
that is not learnt at the first attempt.

If something is scratched fairly badly all over you first have to make
it look worse, with say some 1000 grade wet-and-dry (wet). You now
have something free of scratches but opaque. Then you start with the
finer grades till you get to the stuff that feels more like plain
paper. ;-)

Once you are done there, T-Cut and finer cutting compounds to get it
nice and transparent again. ;-)

Much like the scary sharp technique for sharpening chisel blades where
you end up with a mirror surface at the cutting edge.

Possibly look at some Youtube videos where they embed something in
resin, turn it on a lathe and then polish it to a glass surface finish.



--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

On Wednesday, 1 July 2020 22:30:58 UTC+1, Martin Brown wrote:
On 01/07/2020 22:15, Clive Arthur wrote:
On 01/07/2020 19:24, Brian Reay wrote:

I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form
'light pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?

If you have a spare to practice on, I'd sand the end best you can then
wave it in a blowtorch flame.

Flame polishing might be the easiest solution if it doesn't have to be
optically flat.

+1, it's way way quicker. Should be good enough for an LED light pipe. In some cases rough is good enough.


NT

On 01/07/2020 22:15, Clive Arthur wrote:
On 01/07/2020 19:24, Brian Reay wrote:
I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form
'light pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?



If you have a spare to practice on, I'd sand the end best you can then
wave it in a blowtorch flame.

No need for blowtorch. Standard polishing - finer up to 1200 grit
wet-and dry, followed by T-cut or similar.


--
"The great thing about Glasgow is that if there's a nuclear attack it'll
look exactly the same afterwards."

Billy Connolly

On Thursday, July 2, 2020 at 3:23:32 AM UTC+1, The Natural Philosopher wrote:
On 01/07/2020 22:15, Clive Arthur wrote:
On 01/07/2020 19:24, Brian Reay wrote:
I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form
'light pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?



If you have a spare to practice on, I'd sand the end best you can then
wave it in a blowtorch flame.

No need for blowtorch. Standard polishing - finer up to 1200 grit
wet-and dry, followed by T-cut or similar.


--
"The great thing about Glasgow is that if there's a nuclear attack it'll
look exactly the same afterwards."

Billy Connolly

In the time taken to read this, you could have done an end

On 02/07/2020 06:57, misterroy wrote:
On Thursday, July 2, 2020 at 3:23:32 AM UTC+1, The Natural Philosopher wrote:
On 01/07/2020 22:15, Clive Arthur wrote:
On 01/07/2020 19:24, Brian Reay wrote:
I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form
'light pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?



If you have a spare to practice on, I'd sand the end best you can then
wave it in a blowtorch flame.

No need for blowtorch. Standard polishing - finer up to 1200 grit
wet-and dry, followed by T-cut or similar.


--
"The great thing about Glasgow is that if there's a nuclear attack it'll
look exactly the same afterwards."

Billy Connolly

In the time taken to read this, you could have done an end

Yup. Well I couldn't. I don't have any perspex.


--
If I had all the money I've spent on drink...
...I'd spend it on drink.

Sir Henry (at Rawlinson's End)

Used to be a product called Perspex polish in a tube tat looked like some
substance in a kind of lint stuff.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"T i m" wrote in message
...
On Wed, 1 Jul 2020 19:24:46 +0100, Brian Reay wrote:

I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form 'light
pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?

Fine wet-n-dry (going finer as you go, possibly used wet), held over a
very flat surface and the rods held up as a bunch of 4 taped together
if they are very close in length ... or individually if not and rubbed
back and forth whilst rotating slowly till the finish is a good as can
be, then finish with some T-Cut or similar on some cotton / denim,
also held tight over flat surface.

Or if it doesn't matter if the end isn't perfectly flat and you don't
mind a bit of scatter, use a polishing mop and wax on a Dremel,
keeping the speed down.

If it were here I might first put them in the lathe and then put them
on the linisher.

Cheers, T i m

The Natural Philosopher pretended :
Yup. Well I couldn't. I don't have any perspex.

Brian has some!

On 02/07/2020 03:23, The Natural Philosopher wrote:
On 01/07/2020 22:15, Clive Arthur wrote:
On 01/07/2020 19:24, Brian Reay wrote:
I need to polish the ends of a few (well 4 bits) of short perspex
rod, about 3mm in diameter after cutting. The bits of rod are to form
'light pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?



If you have a spare to practice on, I'd sand the end best you can then
wave it in a blowtorch flame.

No need for blowtorch. Standard polishing - finer up to 1200 grit
wet-and dry, followed by T-cut or similar.


Agreed. I can't see flame polishing working on perspex, the gap between
"no effect" and blistering the surface is vanishingly small.

Access to a metallurgy lab would be good, they usually have a set of
five different papers set up in a bench stand at about 10 degrees, with
a water dribble across them, for hand polishing. They also use machine
polishing, but remember that they mount metal specimens in thermosetting
plastics, either epoxy or bakelite.

On 01/07/2020 19:24, Brian Reay wrote:

Any ideas how best to polish the ends?

I was going to ask the same question,

I'm sure there's something you can wipe on....

On 02/07/2020 09:47, newshound wrote:

snipped

I can't see flame polishing working on perspex, the gap between
"no effect" and blistering the surface is vanishingly small.

Yet somehow it's done all the time and is quite easy. 'Flame polishing
acrylic' is a good search term. Perspex is PMMA is acrylic.

--
Cheers
Clive

In article ,
Brian Reay wrote:
I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form 'light
pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?

Same as you'd do with wood or metal - get as smooth as possible using the
same methods. Then Brasso to polish it.

--
*Starfishes have no brains *

Dave Plowman London SW
To e-mail, change noise into sound.

On 01/07/2020 20:50, newshound wrote:
On 01/07/2020 20:10, T i m wrote:
On Wed, 1 Jul 2020 19:24:46 +0100, Brian Reay wrote:

I need to polish the ends of a few (well 4 bits) of short perspex rod,
about 3mm in diameter after cutting. The bits of rod are to form 'light
pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?

Fine wet-n-dry (going finer as you go, possibly used wet), held over a
very flat surface and the rods held up as a bunch of 4 taped together
if they are very close in length ... or individually if not and rubbed
back and forth whilst rotating slowly till the finish is a good as can
be, then finish with some T-Cut or similar on some cotton / denim,
also held tight over flat surface.

Or if it doesn't matter if the end isn't perfectly flat and you don't
mind a bit of scatter, use a polishing mop and wax on a Dremel,
keeping the speed down.

If it were here I might first put them in the lathe and then put them
on the linisher.

Cheers, T i m

Speed is definitely your enemy when polishing thermoplastics. I've been
trying to polish a bit of "UV haze" out of some plastic headlights
(carefully doing my practice on a bit of dummy plastic at the side, well
out of the beam, just sitting in front of some decorative "chrome").
Even using a polishing mop in my cordless angle grinder at the minimum
speed (which is pretty low), it's easy to melt the surface if you press
a bit too hard.
I used one of the headlamp restoration kits to sort-out the hazed
headlights on my old Saab 9-5. A slightly worrying process at the start
but the end result was great and the lights continued to look good until
I sold the car. I think my kit started at around 500 grit and went up to
3000 or 4000 in 5 or 6 steps, then there was a final stage of polishing.
It was all done with a drill and was fairly quick, with no problems.

On Thursday, 2 July 2020 09:47:10 UTC+1, newshound wrote:
On 02/07/2020 03:23, The Natural Philosopher wrote:
On 01/07/2020 22:15, Clive Arthur wrote:
On 01/07/2020 19:24, Brian Reay wrote:

I need to polish the ends of a few (well 4 bits) of short perspex
rod, about 3mm in diameter after cutting. The bits of rod are to form
'light pipes' in a display- each has an LED at one end.

Any ideas how best to polish the ends?



If you have a spare to practice on, I'd sand the end best you can then
wave it in a blowtorch flame.

No need for blowtorch. Standard polishing - finer up to 1200 grit
wet-and dry, followed by T-cut or similar.


Agreed. I can't see flame polishing working on perspex, the gap between
"no effect" and blistering the surface is vanishingly small.

it's industry standard practice.

Access to a metallurgy lab would be good, they usually have a set of
five different papers set up in a bench stand at about 10 degrees, with
a water dribble across them, for hand polishing. They also use machine
polishing, but remember that they mount metal specimens in thermosetting
plastics, either epoxy or bakelite.

you sure like hard life


NT

On 02/07/2020 09:43, Harry Bloomfield wrote:
The Natural Philosopher pretended :
Yup. Well I couldn't. I don't have any perspex.

Brian has some!

Not yet, it hasn't arrived ;-)

Thank you for all the responses.

I was intrigued by the blowtorch- especially as the bits in question are
about 10mm long (or will be when cut)- If the idea works, they will be
tiny 'light pipes' over some (small) LEDs on a PCB so they can be seen
when the PCB is in a box- removing the LEDs to move them isn't
impossible but the PCB isn't the best quality and I'm not convinced the
tracks/pads will survive. (I planned on a clear box originally - the PCB
was assembled a long time ago- but the one I had in mind is no longer
available.)

--
https://www.antislavery.org/slavery-...forced-labour/