How to cut circles

[rickshaw]

I need some means to cut circles of about 15mm diameter out of thick plasticard.   Any suggestions?

[darthspud]

desk hole punch?
Hand riveter tool?

[Hobbes]

I've tried several methods:
1. a template of the correct size to cut around
2. a drafting circle template
3. a compass cutter

1. depends on finding a template of the right size
2. my circle template is a plastic item made by Rotring, meant for drawing rather than cutting. The template is made in plastic, which means my scalpel will happily cut the template instead of the styrene underneath. Not ideal.
3. leaves a pinhole in the middle of the circle, and I find it rather difficult to cut a neat circle. I always end up cutting a spiral instead.

IOW, you may have to cut a rough circle that's slightly too large, and then sand down to size.

[Mossie]

Another problem with the compass cutter is most have a minimum radius, usually 10mm so you can't cut a circle less than 20mm.  I saw an article where the guy attached a scalpel blade to a pin or needle with a spacer cut to the correct radius.  If the plastic is very thick you might have a problem with it not being robust enough, but carry on enough times and you should be able to score a circle deep enough to pop it out.  I've done this with compass cutters on a much larger circle of plastic about 20 thou thickness.

[NARSES2]

Small hole cutter ? I've seen them go down to 20mm, not sure about smaller

[kitnut617]

There are 'hole punch' sets you can buy.  Usually used for cutting leather but does work on styrene.

If you're not worried about a small hole in the center, hole saws work too

[pyro-manic]

I've been struggling with this recently, trying to cut out circles about 12mm diameter to blank off the wheel wells of a P-40. I used a compass cutter, but the minimum diameter is 10mm, so it's rather awkward. Managed it eventually, but there were several aborted attempts.