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as title - how big is the hole?
9mm . . . ish.
M8
Digital caliper and Renthal chainring says 10.01mm
And the bolt is 9.94mm
Assuming it's Shimano triple then tech document would suggest M8 x 9.2.
[url= http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FC/EV-FC-M760-2261D_v1_m56577569830608893.pdf ]Clicky[/url]
As there's two conflicting replies then probably best to measure with a vernier caliper.
M8 is the thread size.
The holes in the chainring match the external diameter of the female threaded half of the nut & bolt, which has got to be bigger than the thread itself.
You're right. 😳 I assumed OP meant the thread.
Note to self; must learn to read!