....Fab up a drill bushing holder and buy a gun drill, hold in tailstock, have at it?
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If you have the length this can be done as a sort or make-your-own gundrill.
You can even eliminate the bushing if you can bore a straight starter for the drill. (drill a bit under and plunge bore with a endmill).
Gundrills do require blow through to move the chips out and high pressure works best.
Remember that they only have one effective tooth so feed rates need to comply with that.
OR- find a source with a high pressure gundrill. It might be worth your time and effort saved.
Twist drill this length wind up and unwind like springs when pecking.You have to go so slow and the tip has to be centered just so right on the body.
A OD guide land like a reamer side for the first bit of the drill helps keep you from wandering, snaking and locking the whole thing up. Sort of making a flexie gun drill with two flutes but now that becomes a very special made tool.
I'm surprised you get away with the poke,poke,poke method at all at your max lengths in pre-hard.
Care to share cycle time doing so?
I'll go first with a gun drill on production parts so very optimized. 20-26 inch long, same hole and about same material with a carbide gun drill.
2-3 minutes per part but a dual drill spindle machine so 40 parts per hour. I know way slow and yes, this was a major bottle neck in the flow.
Some like their axle shafts solid, some like them cored and others like them tubes. You make what they want.
So easy to poke this hole in the CAD in any material, maybe not so easy for those who have to actually make it.
Is this one to ten holes or ten thousand and more over the next one to two years?
Bob