Drilling Holes in Foam

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.

This is why I needed to drill lots of holes in foam: Track feeders; Points wiring; Servo Mounting plus other odds and ends.
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 battery 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 marks on the “drill” indicate just how deep I need to go for the servos.
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. But anthing will do eg. a piece of dowel or plastic can be hand filed while spinning in a power drill and have a (say) 6mm 1/4″ hole drilled through.  Or fill the end with epoxy and drill a hole.
A hole is necessary through the middle so you can use something to push the waste foam out.
Pushing the waste out… and below:

Here 4 holes have been quickly drilled to accept a servo with minor trimming.
MORE DETAILS ON MOUNTING SERVOS IN 50mm XPS FOAM – COMING SOON
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.
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 above 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).

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Rick Fletcher

Born in the steam era and developed an interest in railways when given a clockwork Hornby "set". Surrounded by steam when travelling to school (by train of course) and holidays were always by steam train as we had no car. How lucky was I?

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