Star-M Adjustable Circle Cutter

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Words and photo: Raf Nathan

Carpenters and woodworkers often need to accurately drill holes for mounting items or other specialised purposes. For some building work a near-enough round hole may be sufficient, however my quest was for a large hole cutter that would be quick to use and leave a clean finish.

My first attempt was an adjustable drill tool purchased from eBay that turned out to be pretty useless. With steel cutters and solid construction it looked good, but struggled in 12mm plywood to drill a hole that was almost round.

The Star-M tool from Japan is ruggedly built with a thick pressed steel body that holds two tungsten tipped cutters which are mounted on adjustable arms running on thick threaded rod.

The arms can be dialled in to drill holes 25–75mm in diameter. A fairly accurate etched scale reads the diameter, although for precise work you will need to check the measurement setting with a ruler.

For safety I only test drilled with the tool in a drill press, but providing you use a slow speed, hand drilling would be fine. For work in plaster board and cladding this is of course the only way to use it.

The tungsten cutters give a very clean cut and I found the walls of the hole to be square at 90°. The hole drill is quick to set up and the cutters can be locked tightly in place with large knobs. I found the maximum depth of 28mm was perfectly adequate. A cheaper version is available with HSS cutters but I suggest going for the tungsten version for longevity and accuracy.

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