Reply to "Help: Need tips on drilling large hole in the side of plastic building."

For nearly thirty years I made my living behind a camera doing product photography. Somewhere along the way I started making sets and props out of plexiglass, Acrylic or Lexan. Many of the trial and error lessons I learned I transferred to my hobbies. If I had to cut several such holes as you describe I would cut a 2 X 2 board around a foot long to a snug fit inside your building. I might use a piece of foam rubber like flipflops are made from and place it over the side of the building. Mark where the hole should be and cut it slightly oversize with a knife then clamp the foam rubber against your building using C clamps and a scrap of plywood cut to approximate the same size as the foam rubber.  Or if you cut it long enough to overhang your building you might screw it to the wood core.  I would precut an oversize hole in both the foam rubber and the plywood before clamping.  Adjust the hole saw bit into position and use the slowest speed the press has and a spray bottle with soapy water to keep it cool. Press the cutter against the piece to be cut in short 1~2 second intervals with very light pressure to keep everything cool and spray the water. I could cut this hole with several devices once the jig held it in place, a cylindrical saw tooth hole saw a paddle bit or an adjustable arm cutter. Once the piece is held rigid cutting the hole is the fun part.   If I were cutting one such hole I would still cut a snug fitting core board to mount and hold the 2 x 2 building steady. Then cut a 1/8" space/ gap on the core right where the hole should be.  I would take a divider with sharp spikes and scribe the circle where the hole should be. Now you have a choice switch to a Dremel tool with a fluted cutter bit and cut by hand  "OR" twist your dividers a couple hundred turns and scribe your way through your plastic wall.  Whatever technique you choose the core of wood and clamping the thing rigidly is the key to a neat hole. One more tip after I scribe a circle on plastic I will run a black dry erase marker over the scribe mark then use a soft cloth to wipe at 90 degrees across the scribe mark makes seeing it with old eyes much easier.  If your building is painted this may not be a good thing. Step bits will certainly make a hole but it may look a bit ragged compared to other methods.  While I like Forstner bits all I have are over 1" and there again are not as neat on thin materials. Guessing the walls of your plastic building are only about 1/16" thick. The fact that you have to deal with an assembled building and not wanting to crush the thing makes the process so much more difficult.    j