Drilling 3/8" counterbore holes

[gary_n]

I am needing to drill 6 3/8" counterbore holes in 110 pieces of 3" walnut, and the pilot hole needs to go all the way through. Has anyone done something similar? Any suggestions for bits, drills, rpm and feeds would appreciated. I tried a 4" long 3/8" counterbore drill in my rounter, but it appears the rpm was way too high and couldn't be slowed down enough. Also the pilot bit keeps breaking.

[beacon14]

Any chance you can go 1 1/2" deep from each side?

Otherwise this might be best done on a drill press.

[gary_n]

You probably could drill the pilot holes from either side. Running the pieces through the 'Bot sure simplifies the hole location on the individual pieces, especially with 110 pieces and each pieces being drilled 6 times. It is looking like I may use a 1/8" bit drilling 1/4" deep to mark each hole and then move to a drill press. All holes need to be uniform as this piece is part of a chair back.

[bcammack]

Pocket screw bit in a drill press? Using a template to register the hole locations?

[gary_n]

That my be just the right combination, or 'Bot and pocket hole bit.

[wmcghee]

Could you take a regular 3/8 drill bit and drill all the way through the wood on all 110 pieces, then when they are complete go back with a 1/4" bit and circle mill all of the counterbores? Just make sure you have a good way to relocate the parts. If the counterbores are deeper than say 1" or so you use the c'bore pilot on the drill press.

[gary_n]

No, the 3/8" portion is the counterbore and extends only 1 5/8" into the 3". Thanks for all the suggestions. What is working the best at the moment is a pocket hole bit and then drilling the pilot hole all the way through.