On 02/07/2020 13:41, Thomas Prufer wrote:
Given: plywood, jigsaw
wanted: circular bit of plywood, diameters 60-80 cm, small hole in the middle is
OK.

Yeah: "make a jig", i.e. an arm with the wanted radius, attached to the jigsaw
base, screw middle down and cut around.

But: I seem to recall there's a catch there somewhere, or a best way of doing
this, in positioning the radius arm with respect to the blade. Should the radius
arm attach to the jigsaw a) ahead of the blade, b) exactly off to the side of
the blade, or c) further back from the jigsaw blade?


A holesaw will leave you a circular bit of ply:
https://www.screwfix.com/c/tools/holesaws/cat5920018
TW