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i was wondering what everyone uses to cut circles in styrene, especially smaller ones.

Olfa Circle Cutter


for poking holes in stuff, an R/C Body Reamer

Yup, me too. Unfortunately, I haven't found any good way to create small discs of polystyrene - the circle cutters can't handle small radii.

Leather hole punch for making very small discs like Orky rivet heads.







Olfa cutter for larger discs. 20mm is probably the smallest you can make with this tool.

A circular section file for reaming out holes.

For cutting circles in polystyrenes I stick an upturned nail onto the deck of my table hot wire cutter and push the styrene down onto this , then I can turn it round against the hot wire allowing me to cut a pretty perfect circle if that makes any sense

a hot wire cutter will cut styrene? your method makes perfect sense, i just didnt think that it would cut the material.

Extruded Polystryene foam and Plasticard are effectively the same material - only the density is different.

You can cut sheet styrene easily enough with a hot wire - you just need to watch your feed rates. Just like with foam - too fast, and you can snap your wire. Too slow and it will melt an uneven line.

But, yes - for smaller circles...punches are the king. The leather punch which Killkrazy linked to works well and gives a pretty good selection, but paper punches expand it even further and can normally punch through styrene up to about 0.75 mm thick (can probably do thicker than that with some of them...but the issue ends up being the throat not being wide enough to accept it).

With the paper punches though - you can get some very tiny holes all the way up to over an inch (with the scrap booking punches). Another thing to keep an eye out for are useful shapes other than round with them. Cutting holes in the middle of plastic is a bit of a pain. With the proper punch though - you don't have to actually cut anything. Line up the punch and just knock them out. Works quite well for vents, windows and certain shapes.

Craft punches are great for creating small discs, e.g. for rivets, but they're only designed for paper and card, so only use them on thin plasticard.

Using them to create holes takes a lot more care - the blade punching through the plastic puts a lot of stress on the surrounding area

Haven't seen any around the inch size - I must keep a look out.

What sort of diameter are we talking, here? "Small" in a more general "fraction of an inch" sense or tiny (that being "small to a 28mm modeler")? Also, are you looking to make disks, round holes, or both? Some tools have a kerf, locating pins, etc. that will mar one side or the other.

For very thin styrene or card, I use common hole punches. 1/4" and 1/8" aren't hard to find as office supplies, but I've only found 1/16" at craft stores. Being meant for thin paper, the shear is usually pretty clean (minimal slop between punch and die), but they struggle on even relatively soft materials thicker than 1mm. Both hole and disk are useable, with slight distortion of the edges.

For medium thickness styrene sheets or thicker cardboard/matboard, I use a rotary leather punch. These actually cut with a blade, so materials that don't stretch like leather can get a bit distorted. Cutting edge is usually ground in from the outside, leaving a perfect disk and a slight inward taper to the hole.

For the really beefy stuff, I use a metal hole punch. Harbor Freight's cheap knockoff of a RW #5 Jr. to be exact. Interchangeable punch/die sets give me about half a dozen sizes between 3/32" and 9/32" to choose from and the compound lever action makes styrene feel like a pat of butter when you punch through. Major downside is the central locator pin - a little conical protrusion in the center of the punch - that mars the disk. The bump it embosses can be shaved/sanded down on larger sizes that only need one clean face, but the smaller disks look like little Asian straw hats.

Anything the metal punch can't handle simply isn't meant to be punched. Saws, drill bits, hole saws, and plug cutters (depending on exact size and purpose) are the order of the day for those materials (MDF, wood, thick acrylic, etc.).

For larger diameter circular cuts (it can scribe and draw, as well, if you swap out the blade for a metal or lead point), I have a C-Thru circle cutter. Same basic design as the Olfa, just cheaper. It handles 1-15cm diameter cuts - as big as any of my compasses could draw for freehand cutting. When I've gone bigger (beyond the realm of 28mm modeling, at this point), I just tied a pencil to a string, stuck a pin in my center, drew the circle, and cut/sanded to shape.

thanks all.
i was thinking of circles like 1/2 inch in diameter, too big for the leather punch and too small for most of the tools that ive seen. i might give the metal punches a try and see how they work.
worse case scenarios cut and file. i just dont have much luck doing it that way.

Here you go for a .5 inch...

http://www.amazon.com/EK-Tools-Circle-Punch-0-50-Inch/dp/B0090JVDNA/ref=sr_1_5?