Drilling Holes in Foam at "Kalrail"
Rick Fletcher - NSW Australia

Updated 25 June 2016

Since my layout uses foam sheets as a trackbed, there is a need to drill holes, often many of them, through the foam.

The drill used is made from a piece of metal tube. I use brass tube which does the job and is available in in a variety of appropriate diameters (eg. K&S). I use two main sizes:

  • 6mm for track feeders and points (turnout) wiring.
  • 12mm for mounting Servos in foam
  • + 10mm for other odds and ends
You could use aluminium tube but it doesn't hold its edge well. Steel tube would work well if you could get the size.
Prepare the cutting edge by bevelling the end of the tube on the INSIDE.
I carry out that operation on a lathe using a scraping tool but it could be done in a drill for short tube drills.
It may even be possible to use a tapered reamer to form the bevel. There may be a need to touch-up the edge from time to time.

Use a hand drill on a fast speed. This 12mm hole is through 50mm foam to fit a micro servo
(eg Tower Pro SG90 or my preference Micro 9g Metal Gear Servo)

The result is a very clean hole

For 12mm brass tube it is necessary to reinforce the end held in the drill to prevent crushing.
I machined a small piece of aluminium in the lathe (about 20mm long) and epoxied it into the top end.
A hole is necessary through the middle so you can use something to push the waste foam out.
You could use a tube of plastic or wood the right size or
file it down in a drill. Or fill the end with epoxy and drill a hole.
Push the waste out.
Here 4 holes have been quickly drilled to accept a servo with minor trimming.
In this photo a hole was drilled under a point to carry the wiring from the micro switch under the layout.
Note the use of a length of paper drinking straw to line the hole so that the chemicals in the foam don't attack the wire insulation.
The straw is held in place with a dab of PVA woodworking glue or similar.

This is the underside of the layout showing five 6mm holes, lined with a drinking straw, to carry track feed droppers.
The centre 6mm hole carries 3 wires from the microswitch fitted to the point.
The 4 x 12mm overlapping holes have accommodated the micro servo and its connecting wire.

These are the drills I have prepared. The 2 on the left are 6mm (OD) with the longer one used to go through 200mm of foam and the shorter one for all of the feed wire droppers. The 6mm Brass tube does NOT require reinforcing in the end where it is held (but don't overdo the chuck).
The next two are 12mm which is the exact thickness of the micro servos. The long one goes through the 120mm foam sheets I have used (not recommended) and the shorter one for the extruded 50mm foam. This is used for the servos.

Working Expanded Styrofoam (EPS) can produce a SNOW STORM!!
I use a suitcase type vacuum cleaner with the nozzle directed at the work area whenever shaping EPS
The drilling process is fairly mess free but care needs to be taken when pushing the waste out of the drill.

The attachment shown below holds itself on by suction and has a hole to accept a drill to capture waste before it escapes!
Brilliant for working up under a layout. My suitcase type vacuum came from a local chain store (BigW in Australia).