Chainring bolt hole diameter
 

Does anyone know the diameter of a chainring bolt hole? Not the BCD, I already have that...I just am trying to figure out the diameter of the hole that the bolt and bolt set goes in. Is there a standard width?

My buddy who works at a machine shop is making a custom bashguard for me and that is the only measuremnt I don't have.

Thanks for any help!

I just measured a bunch of chainrings. For 74 mm bcd granny rings, Shimano, Campy and Suguino rings all had 8 mm bolt holes. For outer rings on standard road (130 mm bcd) and compact (110 mm bcd) cranks, the bolt holes were all 10 mm.

If yours is a MTB crank, thes values may not be accurate.

Since MTB cranks use essentially the same chainring bolts as the road bike cranks (required lengths may be slightly different), the required bolt hole diameters on the chainrings should also be identical.