I believe the correct size bit to drill out a .370” hosel is 9.4mm. In absence of having the correct size mm bit is 3/8” acceptable? Same question would apply to a .335 hosel. What would be close enough to a 8.6mm?
For a 8.6 mm (R size), you can use a 11/32 bit. It’s readily available at Home Depot, they also carry the R sized bit.