[Brian FRF]

We bore a lot of 1" thick plates with 3-4" diameter hole, currently using 2 flute 1" indexable mills to do it, after drilling 1" hole for access. Looking for something faster and quieter ideally!

Thinking 3 or 4 flute should be quieter, as at least one insert would be in contact with material almost all the time. We run a spiral feed out for chewing the hole into chips, running 70-80% of cutter diameter.

Never used one, annular cutter maybe? Not finding any drills over 2" diameter.

Would 4 flute be quieter than 2 flute? We're running at 2400 rpm feed at 25IPM, cut depth of .18-.25" per pass

[ALongGuy]

No drill. Use a square shoulder inserted endmill/facemill. 1-1/2" for the 3" bore. 2" for the 4" bore. Helix through the material from solid.--Helix - not spiral. More flutes would be better. Use air to evacuate the chips. Then interpolate the diameter with the same tool once you are thru.