Acrylic: End-of-hole polishing?

[GrahamRounce]

Hi - I want to put a 3mm LED into a 3mm blind hole in acrylic.

The sides don't matter, but I'd like the end of the hole polished, not necessarily flat, to let maximum light through.

I'm currently imagining a Dremel with a cut-off mandrel with a tiny Brasso-soaked cloth somehow attached, but I'd be glad of anything better!
Thanks again,

 

[Ollie78]

You can get those tiny felt polishers for dremels, might need to trim it a bit.

Or maybe a flame polish, a tiny bit of alcohol in the hole and light it. Better practice on an offcut .

Ollie

 

[ChaiLatte]

A blind hole might be difficult. Any rotating tool you poke down it that is concentric with the hole has exactly zero rotational speed at its centre.

The surface speed of the polishing medium will vary between a maximum at the outside and almost zero close to the centre, at best leading to variable results.

Your options are constrained by the depth/diameter ratio of the hole. If it is very shallow, you have more chance or angling the polishing apparatus, but if it is a deep hole, you have no space for this.

Would it be possible to use a through hole with polished sides and then plug the end with something you have polished as a flat or concave surface? You could look at how concave lenses are polished for ideas.

 

[niall Y]

Many years ago, I made a light box in acrylic, drilled out for LED s. I used two pieces of Perspex - the one drilled out to form a matrix, holding the LEDs, and the other positioned on the top

 

[GrahamRounce]

Ok, thanks all, for the suggestions. I'm not familiar with flame polish, whether it's a stuff or a technique. I can look it up though.
Thanks again.

 

[Sideways]

Bounce the light down round acrylic rod ?
Drill right through so the led just protrudes and polish it back flush with the surface ?
Modern pinpoint LEDs ?
Just wondering if there are some alternative ways to solve your problem

 

[Phil Pascoe]

It's a while since I polished the end of a hole so I can't help with that one.

 

[graham88]

Why not make the hole a tiny bit deeper and just put a small drop of acrylic lacquer or something similar down the hole? Just thinking how small scratches disappear when lacquered over on car headlights and the like. Not speaking from any experience but it could be worth a try?

 

[Fergie 307]

I would be inclined to try making the hole with a four flute end mill. Never thought about what you are proposing, but use this method all the time in various plastics and leaves a very clean bottom !

 

[Ollie78]

Ok, thanks all, for the suggestions. I'm not familiar with flame polish, whether it's a stuff or a technique. I can look it up though.
Thanks again.

Basically you are just melting the very top surface which then flows to a smooth finish. Normally performed on the cut edges of sheets. A quick flash with a blowtorch is enough. Not sure how it would work in a hole. You can also do a similar technique with a solvent that flashes off quickly, has to b the right one for the material of course.

Ollie