I'm trying to scratch build but I'm stuck on cutting circles out of styrene. Is there easy way or tool that will let me cut clean circles around a 1/2 inch or less in diameter.

Thanks

You could try a tool shop for circular punches like those used in tooling leather. I picked up a chepo set that goes from .125 - .625 of an inch. Not a really clean cut but a good set should work better. Depends of course on what thickness you plan on using.

Hey Alex,
Here a simple way I go about cutting out circle disc, trace out the diameter then using your hobby knife cut lines close to the pattern, but leaving the pencil lines (fig. 1and fig. 2)

Then just sand down to your pencil line (fig. 3). This can be done in just about all diameters and thickness of most plastic.



Joe

get a set of drawing dividers (like a compass but with points at both ends) and hone one of the points to a sharp edge. Use this to score through the plastic.

The smaller style of dividers that have the ability to be locked to a particular size are best.

OLFA Circle Cutter

Damn! You beat me to it - the Olfa compass cutter is a totally brilliant tool, but you have to be doing a fair amount of scratchbuilding to justify buying one.

Joe's suggestion seems the most practical - thanks for that one

I've found that a really sharp scribing tool and a circle template work quite well for thin (up to .030) sheet. Firmly hold the template over the sheet and scribe around the edge of the hole numerous times until it cuts through. Numerous light cuts works best.

Norm Samuelson

I have asked this question before and have recently bought this from e-bay and must say it is a superb bit of kit and it was cheap Circle cutter

redleg

I have the second circle cutter. It was worth a try as it only cost about $5. It is not the perfect solution to this problem, but it works well on circles about 1/2 or greater (up to about 6"). This process can take a lot of time, but if you chuck the circle cutter into a battery powered drill...... You get the idea, but be careful to go slow (still faster than by hand) and also use the tool backwards so that the spine of the blade is scribing not cutting. To help with the awkwardness of this setup (as you will find) place the cut down size of styrene onto a wad of poster putty. I still recommend that you draw the circle with a divider first so that you can tell if you are staying on track and also to create the initial divot at the center point. I have cut up to 1.5mm with success. Did I miss anything? Just be very careful you can imagine what will happen if the tool bites the plastic while you are still pulling the trigger. Dont go too fast (hence the battery powered drill)!

Another way to cut circles is to use a hot wire cutter. Do not breath in the fumes!!! This still only creates a rough cut so its not really the best. I have used hole saws but that will only work if you can deal with a 1/4" hole in the center and 1" size or larger. For smaller holes I have a leather punch and just a cheap hole punch. Chances are it will be the wrong size anyway, but close can count sometimes.

For smaller holes I think the best way to accomplish cutting them is as follows.
Cut a square slightly larger than the size you need. Next grab a small tube or pipe with an OD (outside dimension) of the size circle you want. Place the tube over the square centered. Now using a hobby knife, trim the excess material away all the way around. I have heard about using pipe to punch out circles, but I could not make it work too well, thats when I came up with trimming around the pipe. Necessity is the mother of all invention...right?

Good Luck!

I have used dividers and circle cutters, but both leave less than desirable edges which need fixing. I like to just cut a quick rough circle of styrene, and chuck it on a Dremel. A few seconds on a file, the wet/dry paper yield a perfect circle with a nice uniformly perpendicular edge. Fill the center hole with CA and sand smooth. (Much quicker than putty.) I've used this for the brake discs on the resin Aimodel M198, the hatch armor on the M109A6, and several other things, and it literally takes seconds. No pics handy, so I'll repost this one that's already loaded on Photobucket- M12 wheels cut down to the proper diameter to use as spacers using the same method: