Cutting Plexiglass

[doodledee]

Anyone have any tips for cutting plexiglass in a round shape to avoid those pesky chips?

I know to use blade with many teeth. I have a jigsaw and a dremel. I have cut rounds before and I usually use the jigsaw w/o rip fence because I can't find one for the jigsaw where I live. I leave a bit of space between the cut and desired edge and finish it out with a file to smooth out the edges. Hopefully someone has some better ideas.

Thanks

[pencilist]

Originally Posted by doodledee

Anyone have any tips for cutting plexiglass in a round shape to avoid those pesky chips?

I know to use blade with many teeth. I have a jigsaw and a dremel. I have cut rounds before and I usually use the jigsaw w/o rip fence because I can't find one for the jigsaw where I live. I leave a bit of space between the cut and desired edge and finish it out with a file to smooth out the edges. Hopefully someone has some better ideas.

Thanks

I used a dremel with the multi-purpose cutting bit. It works fairly well but it's a pain as you have to keep stopping to clean the bit...the plexiglass melts as you cut and gums up the bit. Then I used the grinding thing that looks like a drum to fine tune the openings. I still had a tough time but I was doing straight cuts too, which seem harder to me than circular ones.

A band saw is supposed to work well, but I couldn't find the blades I needed for mine. Also a coping saw with as you said lots of fine teeth.

I think had I practiced more with the dremel before diving in, it might have been an easier go.

Lorraine

[doodledee]

Thanks for the advice Lorraine, I don't have a band saw so I think I'll have at it with the dremel. Wish me luck!

[Merlion]

You have not mentioned how thick is your plexiglass sheets, and what diameter is your circular cut. What tool is best depends on these.

Many bandsaws have wide blades and thus would not be suitable exceot for large circular cuts, say 24 in diam or larger. Handheld jigsaw blades are not as wide and are thus better for circles say 10 in diam or larger. Machine jigsaw blades are narrow, but tend to break easily.

[doodledee]

Hi Merlion, The circular cuts I've made so far have been about 24" in diameter, 1/4 inch thick. I'm looking to make a circular cut of 34" or 36" and believe I'll need to work on something a bit thicker to minimize flex under stress or pressure. I'm waiting to make decision on thickness until after I get some more feedback. While plexiglass is not terribly expensive I don't really want to destroy a sheet of it due to inexperience.

Thanks for your reply, De

[MoonRise]

Several ways to do it, depending on tools/tooling available and production speed and desired 'finish' and tolerance (how close to the size and 'perfect' shape you need or want).

One way would be to rough-cut with a band saw or jig saw. Then finish cut with a router following a template (for repeatability and tolerance confidence). Or run the rough-cut plexi on a central pivot (jigged or attached) and sand to final size/shape with a disc sander or drum sander.

If a sanded/frosted edge is not desired, you can run progressively finer grits and move up to buffing/polishing. Or for acrylic plexiglas (as opposed to polycarbonate like Lexan, which some people mistakenly also call plexiglas), the final step could be a flame-polish. Note that flame-polishing plexiglas can scorch or melt the plastic if you are too hot with the torch or keep the heat in place for too long.

Oh, and slow the bit/blade speed down if possible. High-speed = more friction (especially if you pause during the cut), which means melted plastic.

[Merlion]

To finish off the rough or slightly uneven edge, I use a handheld power sanding machine that gives circular motion. I also use it to round off the sharp top and bottom edges of the circular edge.

[Merlion]

Originally Posted by doodledee

The circular cuts I've made so far have been about 24" in diameter, 1/4 inch thick. I'm looking to make a circular cut of 34" or 36" and believe I'll need to work on something a bit thicker to minimize flex under stress or pressure. I'm waiting to make decision on thickness until after I get some more feedback.

What are you using these circular plexiglass for? To hang up, or to support something? Short term or long term? Nearly all plastics creep (deform with time.)

Have you thought of using glass?