Roughing deep hole Help

[FTI2007]

I need to bore a 6" hole through a 8"x9" block of HRS 14.25" deep.  My thoughts are to rough it with a 2"  feed mill half way from each side and then bore it to size. The problem I see is getting chips outs.  We only have a vertical mill without through spindle coolant/air.  I would like to drill about a 2.5" hole through the center for the chips to fall out but I am not seeing a lot available for that diameter and length.  Unless I drill it half way from each side. It would just add an extra flip to the part.  I need to do 8 parts. 

any other suggestions?  

or suggestions on a drill? 

 

Thanks

[AHarrison1]

Hook up an air line to the spindle head with the nozzle pointing straight down your tool of choice.

That should help with chip evacuation.

[gcode]

We do stuff like this all the time

You are on the right track

Blow a Ø2" hole through it with one of these

Allied Spade Drill 

If your machine doesn't have the horse power to drive a 2" spade drill

drill a 1" hole first

then helix mill it out half way thru with a 2" high feed

then flip it and mill from the other side

A better solution might be to send it out and have it trepanned

You won't spend a bunch of $$$ of tools and you'll get some nice Ø4" slugs back from the trepan house

[FTI2007]

1 hour ago, gcode said:

We do stuff like this all the time

You are on the right track

Blow a Ø2" hole through it with one of these

Allied Spade Drill 

If your machine doesn't have the horse power to drive a 2" spade drill

drill a 1" hole first

then helix mill it out half way thru with a 2" high feed

then flip it and mill from the other side

A better solution might be to send it out and have it trepanned

You won't spend a bunch of $$$ of tools and you'll get some nice Ø4" slugs back from the trepan house

 How well do those spade drills work without through coolant?  Since we do not have it might have to go half way from each side? 

[gcode]

23 minutes ago, FTI2007 said:

 How well do those spade drills work without through coolant?  Since we do not have it might have to go half way from each side? 

Without through coolant you would want to run a peck cycle at about .250"/peck

I'd also run the rapids at 25% to get the coolant lots of time to get down in the hole