If I cut 3mm sheet cork the width of HO ties, will it bend to a radius of a turnout exit of spur (slight) curve?
BB
Probably not easily. Why not use an outline of the turnout as a template to cut the cork to fit the turnout? Then the straight pieces can butt up against the ends of the turnout section with no problem.
Despite my fairly newby type question on another post (Cutting Cork), I have in the past cut cork for underlay, and I can tell you that unless you make strips half the width of HO ties, the stuff won’t bend neatly. For turnouts, I simply splice in the half width stuff and lay it on the alignment of the diverging road, adding the other half once one side strip is down. This is the most economical use of cork sheet stock.