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Does anyone have a "good" way to cut circles from styrene?
I'm modifying a scratch-built HO-scale grain elevator for a friend; the silos are 2" PVC pipe, which I wanted to top with circles cut from .040" styrene. (The exterior diameter of the 2" PVC pipe came out to just slightly under 2-1/2".) After several unsuccessful attempts using differing methods, what I finally came up with was a 2-5/8" hole saw, made for cutting holes in residential doors (to install locksets in). Using the hole saw in my drill press, I was able to get enough "uniformly round" .040" styrene discs to top the PVC pipes (silos). Some sanding and filing was needed to smooth the cut edges, but it worked. The problem with this method is that it leaves a hole drilled in the center of the styrene disk -- which I will be able to cover with the conveyor housing which will run across the tops of the silos. But what if I wasn't able to cover that hole, or needed "solid" disks?
I know (or at least I HOPE!) there is a way to cut circles from styrene, to have multiple pieces in the same size, in whatever size I want them to be, without the holes in the centers, and without taking a ton of time to cut them. But that is something I've not seen in any of the magazines or forums I've looked at over the years... and I can't imagine that I'm the only guy who'd like to be able to do that!
If you are using a drill press then you don't have to use the drill bit in the center of the hole saw. With a portable drill the hole saw will run across the work piece without the drill bit to guide it. With a drill press, you can clamp the plastic so that it can't move. I do this all the time.
On the better made hole saws it's easy to remove the drill bit.
If you want to cut the holes and don't have a drill press, then first bore a hole through a piece of 1/2 or 3/4 wood. Remove the drill bit from the hole saw mandrel and clamp the wood to the plastic you want to cut the circles from. The hole in the wood will guide the hole saw and allow you to cut the circles safely.
I have a pretty good method. I use what's now an old-fashioned device, a draftsman's compass. I put a needle in both sides rather than having a pencil lead in one side, and using it I can scribe a circle, then snap the plastic just as if it were a line done with a knife blade. No need for power tools!
You could fake this for a fixed size by putting a couple of pins through a piece of wood.
What about gluing a circle (rough cut and bigger than the pipe) to the end. Once the glue is set up, use an exacto knife to trim the edges. Then fine grit paper to sand it smooth.
What about gluing a circle (rough cut and bigger than the pipe) to the end. Once the glue is set up, use an exacto knife to trim the edges. Then fine grit paper to sand it smooth.
that's the method I've used. It is a lot more work, but gives excellent results. A benefit is that it also has the advantage of working with slightly out of round tubes (more common than you might think...).
I have an inexpensive children's compass that uses a standard pencil, clamped into the compass. I remove the pencil and replace it with an Xacto knife with #11 blade, allowing me to cut circles in thin material from about 1.5 to 5 inches in diameter.
The best and easiest circles I've ever made were by using a circle punch.
One whack with a hammer and presto!
If you can find someone who works in leather, or someone who cuts gaskets (what I did) you can knock them out in in bulk.
On a side note: I just picked up one of the model power cesna's and peeled off the prop so I will need a circle of clear plastic to represent a spinning blade. I'll bet a website for airplane modelers will have even more methods!
What about gluing a circle (rough cut and bigger than the pipe) to the end. Once the glue is set up, use an exacto knife to trim the edges. Then fine grit paper to sand it smooth.
I use a similar method but doesn't require cutting a circle first.
I cut a square of styrene just slightly larger than the diameter of the pipe or tube. After cementing it in place I trim off the corners and the smaller corners they will leave until it ends up about a 10 or 12 sided diamond shape fairly close to the tubing outside diameter. Then with a smooth file and progressively finer sandpaper work the piece to the pipe shape. The larger corner pieces I cut off go in my scrap styrene box and sooner or later get used as reinforcements or braces on a future project. For thinner styrene like .020 or .015 I just drag an Exacto knife around the pipe after gluing and then sand to finish.
I found this CMP1 Circle Cutter on Amazon.com. It lists on $5.69 .. the dang shipping is $5.89 ... haha. Still .. looks like it would work. One of the reviewers says that he uses it to cut out shapes for building plastic models.
I found this CMP1 Circle Cutter on Amazon.com. It lists on $5.69 .. the dang shipping is $5.89 ... haha. Still .. looks like it would work. One of the reviewers says that he uses it to cut out shapes for building plastic models.
I have one of those... and I was not impressed by how it worked. It seemed as though the blade kept digging into the styrene (Plastruct .040" white) which made it somewhat difficult to get a true circle. Now, in all fairness, that could be "operator error"... but I wasn't impressed.
Im thinking if you dont need the round part that is left when you cut the circle. You may be able to use a hole saw and wouldnt even need to run the drill very fast at all. That way you get a perfect diameter circle.
