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Cutting, sanding plexi.

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Borisw37

Member
Joined
Aug 19, 2003
I found out that its real easy to cut plexi with a circular saw, but it leaves behind a less than perfect edge. I need the edge to be flat and also keep its 90 angle, for gluing.
How can i sand edges of acrylic/plexi pieces and keep them straight (90degrees)?
 
try a blowtorch on the edges, it's always seemed to put a nice edge on it for me, I don't mean to the point of melting it, just run over it lightly, try on a piece of scrap first.
 
i have tried that method, it either does not do anything, or acrylic starts to buble, and the piece is ruined.
 
I used a light file on mine - works well, although it is still a little bit rough textured (not visibly though).

I am thinking of using 600 grit wet sandpaper to finish it off and get it visibly smooth.
 
but when using a file or a sand paper, what guarantess that you are going to get
|_| edge and not rounded or slanted edge surface?
 
You could mount the paper to a sanding block. As long as you payed attention, and not angle the block you could get a flat edge.
 
The edge finish of acrylic is wholy dependant on the blade used.

My table-saw cut came out perfect, but I had a similar thing happen with some score-n-snap pieces, Only I had six pieces that HAD to be the exact same size. Hand sanding wasn't good enough.

I took my old home theatre sub-woofer and strapped a piece of 3/4" particle board to one side and made a 90 degree sanding jig. Clamped all six pieces together and went to town sanding. It took forever though; 1.5" thick total doesn't sand down to fast. Started with 80 grit and went up to 1500.

If you use the 90 degree snading jig method, go slow or you will ever so slightly round off the corners. You won't notice it untill you get above 800 grit then your like "WTF".
 
Discs go from 36-1000 ..... works great :D
However when I order plexi from Tap Plasics, they use a bandsaw with a god only knows how many teeth per inch (im guessing 16-20) which leaves a edge which only has to be sanded with 600. To finish the edge off, I just take a Mapp Gas tourch and run it along the edge, holding the flame 2inch back, making several passes. Too close = warping/bubling, too far away takes for ever. You just need to practice. UberBlue has the idea using a jig, but mine does a little faster job ;)
 
is it possible to put a sanding disc on a dremel, and attach the dremle 90degrees to some flat surface.
Basically make the same thing The Spyder has, only with a dremel
 
use a router... its real easy too... get a bit with a bearing on the bottom and clamp the plexi onto a piece of wood or something with a solid edge makin sure the plexi only hangs over the side as much as you want to take off... the only tricky part is making sure the edges are paralell, one way of doing this is with a measuing tape or some kind of jig to check and recheck the gap, just use your imagination(every time ive done this its been different)... the bearing will basically take out human error once you start cutting...so you wont have to worry about goin in too deep

for future reference a good way of doing it this way is basically cut your window out of wood and sand all the burrs and get a decently smooth edge then make a rough cut on the plexi or lexan a little bigger than needed... next, use double sidedtape to hold the plexi to the wood, use the router to trim off the exess and youll have a perfect cut, then if the edges are showing like was said before use a torch to smooth it... but also you can sand the edges of plexi just as you can with plastic or wood if the edge is bad (you wont have to worry about this with a router)

fyi, i used to do a lot of custom boat work with seaboard( type of plastic used in boats) lexan and plexi so i can probably answer any more questions if you have any
 
Borisw37 said:
is it possible to put a sanding disc on a dremel, and attach the dremle 90degrees to some flat surface.
Basically make the same thing The Spyder has, only with a dremel
:D
You asked for it.....

Heres the setup. 1 dremal, 1 1/2inch thick base station, 1 1/4inch peice of plexi. 1 set of wood guides.

To build this, view image.
090104-sanding station2.JPG

A basic explanation of this setup is as follows:
The base station is composed of 2 peices of 1/4inch plywood, the top one cut to fit the plexi insert, which allows the plexi glass sliding surface to be surface mounted. A 60mm hole is drilled in the 1/2inch base station. The dremal is attached to the wood base, along with a 2 peice back guide system. This rear quide system alows a straight sliding surface, assuming the bit the of set 1/16th of an inch, allowing 1/16th of an inch material removal per pass.
*KEY*
Gray is the plexi base
Brown is the wood
Gold are the screws
 
Last edited:
The Spyder said:

:D
You asked for it.....

Heres the setup. 1 dremal, 1 1/2inch thick base station, 1 1/4inch peice of plexi. 1 set of wood guides.

To build this, view image.

The only problem I have with than is you can't get Dremel drums in high grits.

I've found with the Acrylic solvent glue I'm using, I need to have the edges finished to at least 1000 grit to prevent bubbles in the joints.

I tried the flame polish method but found it gives a slight convex edge which leads to bubbles along the edges.
 
UberBlue said:


The only problem I have with than is you can't get Dremel drums in high grits.

I've found with the Acrylic solvent glue I'm using, I need to have the edges finished to at least 1000 grit to prevent bubbles in the joints.

I tried the flame polish method but found it gives a slight convex edge which leads to bubbles along the edges.
Have you ever tried finding no name sanding drums? I have a box of classifyied 220 gril bits, which were $10 for 12 drums. They fit the dremel drum and work quite well.

How thick is the the plexi are you trying the flame methode on? Also what type of tourch, flame size, path distance and length are you using?

I build plexi sub boxes which have to be PERFECT for the adhesive and screws. The flame methode has to be practiced quite a bit to get it right, but its defn, worth it.
 
The Spyder said:



I build plexi sub boxes which have to be PERFECT for the adhesive and screws. The flame methode has to be practiced quite a bit to get it right, but its defn, worth it.

Looks like you know what you’re talking about (as usual). I made a cylindrical reservoir out of Plexi-Glass. When I glued the top and bottom on some of the glue ran over the edge and on to the out side. It got kind of smeared. My question is, can I polish/clean this glue off the plexi-glass tube somehow? Of course I am talking about cleaning up the Outside of the tube.

PIC of RES You can see where the glue smeared a little by the tape.

Also if you don't mind, what is the best method for cutting 1/4" Plexi?

THANKS
 
Do you have a drill press? If you do go to home depot and get a few sanding drums. Should give you the results you want without having to spend alot of money or time.

Thats IF you have a drill press already. IF not then well you can rig up a belt sander to the edge of a table and use that.
 
In your case, where the glue has smeared, I would wither go to your local plastics supplier and get a plastic polish. The glue I use melts the plastic, bonding the surfaces.

Cutting 1/4inch can be done several ways.
If you have a table saw, a fine tooth blade will provide straight rips, however they will have to be sanded and finished.

If you have a jig saw, get a 15-20tooth blade, setup a guide so that the cuts are straight. Free hand is easy also, but in both cases GO SLOW :D Use a variable speed jigsaw, and use low rpms as to not melt the plastic.

Now If you have a dremal, nothing works better then just a good old re-enforced fiberglass cut off disk. Set the dremal to 15-20k and make sure you have a straight like to follow. Start cutting at one end and move your way towards the other. Some people like to run the disk over the line, I dont do this because you have a greater chance of the bit jumping and scratching the plexi.
Best of luck :D
 
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