Finishing an edge on plexiglass...

[Sinner]

Does anyone know of a good way to finish a drilled or cut edge on plexiglass?  The edge is kind of sharp around my trackball, and I'd like to clean it up, but I don't want to start sanding, if this will damage it...
Thanks...

[SUB ZERO]

A "round-over" router bit will work 

[Stingray]

Router bits will work on plexi, or is this a special plexi bit? Never occured to me to use my router on plexi, I assumed it would crack.

-S

[Sinner]

Kewl...thanks...I used a flush trim bit to route the outside shape of the plexi...I will see about getting a rounding bit and give it a try...thanks for the info...

[Mark70]

Why not do it the old fashioned way.

Sand it with 220 grit silcon carbide paper and then attack it with a buffing wheel attached to your  drill.

I made a keychain in grade 7 made out of three layers of plexi glued together, cut with a hand jigsaw.  All we did was sand the edges then use a bench grinder with a buffing wheel to polish the edges.  It came out shiny and smooth.  That was way way way back when swatches were popular, and the guys would all show up for shop class with seven watches on their wrist, polishing the lens on the girls' swatches.  Actually we had co-ed shop class, but you could chat up the girls who were in home-ec that half of the year by offering to buff their swatches.... oh that sounds worse than it should.

But I digress....

So why make it harder than sand it and buff it?

[stratjakt]

Sandpaper, maybe 150 then 220 then 320 then 400 then 1000 then 2000..  That's silly, you don't need to go that high, just stop when it looks good enough for you (probalby 220, skip the rest).

You can also "flame polish" the edges by heating them with a torch, enough so just the edge melts a wee bit then cools to a nice clear rounded finish.  This takes a bit of practice, since you can easily start burning the acrylic, or melt a bit on the face of the piece.. Once you get the feel of it, it works well.  I've used a propane torch with a really sharp flame, and basically quickly skimmed it down the edge.

Ultimately, though, I'd say a piece of relatively fine sandpaper and about a half hours worth of work would be the best.

[pmc]

Presumably all these techniques work for Lexan as well as Plexi? I know that they are fundamentally different animals, but I don't really care about that as long as the same edging techniques work on both.

-pmc

[AmericanDemon]

We built a chopsaw stand once and behind the saw, the guy wanted a plexi shield that curved.  So we heated the plexi up with a torch and attached it.  Don't really recall how we attached it, but when the guy cleaned it the first time, he used Rubbing Alcohol.  The sucker cracked into a million pieces.  It was a sight to behold.

[Bones]

I cut a hole in some scrap MDF the same size as the trackball hole I had cut in the Lexan and then lined up and clamped the two pieces together. I then used a router to bevel the edge of the Lexan using the MDF as a guide and a rounded router bit that had a guide bearing. The process worked fine and without any problems.

The great thing about this was I could cut it once, decide I wanted to bevel it more and just keep adjusting the router depth until I got the result I was after.

The little dags on the edges are just the protective paper covering, once removed the bevel was very clean and required no sanding.

[nostrebor]

I would do it just like Bones said, and the flame polish it. The trick to flame polishing is practice,practice,practice... And low heat. I just use a little butane torch from Harbor Freight.

[Abomination]

We built a chopsaw stand once and behind the saw, the guy wanted a plexi shield that curved.

[Sinner]

I would do it just like Bones said, and the flame polish it. The trick to flame polishing is practice,practice,practice... And low heat. I just use a little butane torch from Harbor Freight.

What is Harbour Freight??  A store or a brand??

[nostrebor]

http://www.harborfreight.com/

[daywane]

I would do it just like Bones said, and the flame polish it. The trick to flame polishing is practice,practice,practice... And low heat. I just use a little butane torch from Harbor Freight.

What is Harbour Freight??

[Sinner]

I'm in Canada...with shipping, and with charges for bringing it into the country, I think I could find better deals here...I didn't get a chacne to look around too much (I'm at work), but it looks like they have some pretty kewl stuff...

[Ed_McCarron]

Presumably all these techniques work for Lexan as well as Plexi? I know that they are fundamentally different animals, but I don't really care about that as long as the same edging techniques work on both.

-pmc

Don't overheat polycarbonate.  It's hygroscopic - absorbs moisture out of the air.  Get it too hot and you get nasty bubbles as the water flashes to steam.

I've bent plenty of polycarb but never had luck flame polishing the edges.  Getting it hot enough to bend without getting those bubbles takes a steady hand with the heat gun and lots of patience.

[pmc]

Presumably all these techniques work for Lexan as well as Plexi? I know that they are fundamentally different animals, but I don't really care about that as long as the same edging techniques work on both.

-pmc

Don't overheat polycarbonate.  It's hygroscopic - absorbs moisture out of the air.  Get it too hot and you get nasty bubbles as the water flashes to steam.

I've bent plenty of polycarb but never had luck flame polishing the edges.  Getting it hot enough to bend without getting those bubbles takes a steady hand with the heat gun and lots of patience.

Well then, sanding and buffing is just plain fine with me. Thanks for the tip.

-pmc