That’s odd, the TCMT 1102 seems to have a 2.8mm hole through it so should take an M2.5 screw?
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I have several tools that use M2.5 Torx screws and the driver for them is T8.
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If it does turn out to be a T8 Alan I’ve got several T8 Flag style drivers I don’t use so you’re welcome to one.
I have a “Little Hogger” set of milling cutters that I got from Chronos and one of those takes inserts that look like TCMT inserts but are a little thicker I think. I’ve only ever got replacement inserts from Chronos and these use an M3.5 Torx screw that requires a T15 driver which comes with the set.