Cutting Plastic Without Butchery

Drill a whole bunch of holes slightly inside the cut out lines, all the way around. Cut out from one to the next, and I'm speaking of 1/16" holes with less than that in between, with the tip of a knife or a tiny saw. Use files to get to the final opening size.

One trick I like is to mask around the area to be kept, then paint the scrap side a distinct color, like black on tan plastic or white on green plastic. When you are filing out the opening, file to remove white.

Good ideas! Do you happen to have any pictures of the drilling process?

Yep. This is a pair of radiators for a Felixstowe flying boat in 1/72. 

Regular sewing thread can be used as a "saw" as well.

Doesn't really fit all applications...such as the situation GM posted. I use it regularly to cut control surfaces free on aircraft. Take a 15" or so length, tie a small thumb loop at one end, wrap loop around thumb...3-4" later, wrap the rest around your index finger...just work it back and forth (it helps a LOT to first scribe the line to be cut). The friction of the thread on the plastic will cut it (technically, the friction builds heat and the thread melts its way through). It does leave a rough edge that will need to be cleaned up, but does not remove as much plastic as a razor saw.

Interesting, thanks to both of you! I'll try these ideas out on some spare plastic.

For removing a whole section, as in the ship, or removing a section of an airplane fuselage, a razor saw is a quick method of cutting.  The original razor saw was the Zona, a one piece unit of blade and handle, but there are several now, including an X-acto saw blade for use with the larger handle, so you can replace the blade when the teeth are worn.

A tip on using the razor saws with plastic.  They heat the plastic when sawing, so it gums up and gets hard to work.  Water periodically dripped on the blade helps cool the plastic at the cutting line, and makes the cut easier.

Would a razor saw work for smaller and thinner areas? I have to remove most of the sides of the upper hull, as you can see here:http://www.eduard.com/store/out/media/36042.pdf

Don't try to take that side off in one piece. I would make a series of saw cuts perpendicular to the edge of the part, to within about 1/32" of the long cut. Maybe about 1" apart. Scribe the long cut first with a knife or razor blade or scribing tool, again about 1/32" in from the edge of the area to be removed, and snap the pieces off. Finish with sanding stick and file.

Also get an understanding of how the brass part attaches. Does it overlay the cut area, in which case you can leave an edge under? Or does it have to fit in flush.

Ok thanks, I'll try that.

Hmmm.

      I take a p.e. scriber to do my cutting .It's thinner than an X-Acto knife or a saw of any kind .  T.B.

Moff

Would a razor saw work for smaller and thinner areas? I have to remove most of the sides of the upper hull, as you can see here:http://www.eduard.com/store/out/media/36042.pdf

 

razor saws work well for longer straight cuts only. If it is a short cut not at top or bottom of a panel it does not work, nor does it work for curved cuts.  For those I have to revert to the series of holes.

I'm using a combination of the holes and the string, and it's working well. There's some fit issues, but it's my first big photoetch set, so I'll take whatever comes. 

Well, it seems I removed some stuff I wasn't supposed to :( and I could use some tips on how to scratchbuild with sheet styrene. Do your tips differ? The pieces I'll have to scratchbuild are really simple. Basically a two-dimensional trapezoid, with three sides 90 degree angles, and the fourth side about a 40 degree angle. 

Sure. Make it out of paper first, and when you get it right copy it in styrene.

And then scribe or razor saw? The string method is a little too imprecise. 

For simple staight cuts in a sheet of styrene stock, if it is thicker than about 30 mil, the scribe method works (similar to cutting glass).  Scribe a straight line across the piece with a #11 blade, then bend at line over table edge- the piece will break at the line.  You may get a somewhat nicer break if you scribe two lines, one on each side.  However, for that to work the two lines must register almost exactly.

0.30 mm or 30 mm? The styrene that I bought is 0.75 mm or 0.030" thick. Scribing sounds good, and I'll try it. I have plenty of the stuff anyway, and mistakes won't be really costly.

You are getting the picture, bud. The sheet you have is what Don is referring to. You'll be whipping out constructions soon. Another good tool I like for these kinds of projects is a Northwest Shortline "Chopper".

It's great for mass production of same sized parts.

Well, I think that's really the last thing I wanted advice on. Thanks to everybody for responding, even through my incessant and sometimes obvious questions :)

I have some photo-etched sawblades.....I think I got them from Squadron Shop....these are really thin and do a great job.  They come in different shapes and sizes.  The round one is great for starting a cut.....pull-push it with small strokes to start.   There are several shapes in addition to standard "flat blades".  One is pear shaped, wider at the top and pointed at the bottom, with teeth all around.  I recently used them to cut out the flaps on a 1/72 scale Me 262 with great results.  Work slow.  

Also, to cut friction on blades I have rubbed bar soap on the blade.  Tried liquid soap but that gets messy becasue it spreads around.

I have also found that in some cases a standard single-edge razor blade is better that the #11 blade.  The razon blade is of a uniform thikness and works better in some applications.  I place the blade in a "box cutter" that I got at an office supply store.  The cutter holds the blade nicely and cuts down on my need for band-aids.

Have fun.......................

There we go! Squadron you say? I may have to leave the ScaleHobbyist camp...