Deep hole drilling on an engine lathe

[Chipper5783]

Just 1. I think going slow and using the tips in the video above should work well. I'm not considering any 300 series due to the machinability, but may end up with 17-4 for strength.

17-4PH can be quite variable - it depends the hardening process that has been applied. Any 17-4PH condition can be machined, but in the “hard” state it is fussy.

 

[Martin W]

I would be worried about work hardening also. especially if your cutter loses an edge.

 

[verbotenwhisky]

I've cut plenty of stainless, and I'll take 416 over any 300 series other than maybe 303. It'll either be 416 or 17-4. I still need to crunch some numbers to see if 416 is strong enough, but my gut and some quick hoop stress calculations say yes. H1150 will be more than strong enough and machines beautifully. It's just more expensive and I have less experience with it and thus less confidence in my ability to successfully drill it.

I do not know your application so forgive if this sounds dumb; but have you thought about boring it a bit oversized in the 300 series and sleeve it with a tube of a better alloy silver soldered in and ream it to final size with a bore reamer?

 

[biednick]

I think you pretty much need flood coolant. That’s a pretty deep hole.
Martin

Flood coolant is no problem, but everything I've seen about gun drilling involves what appears to be closer to MQL coolant at several hundred PSI. The equipment to do that is fairly expensive, which is why I'm somewhat adverse to gun drilling.

 

[biednick]

17-4PH can be quite variable - it depends the hardening process that has been applied. Any 17-4PH condition can be machined, but in the “hard” state it is fussy.

In my experience H1150, the softest hard condition, machines very well. Condition A has given me the most trouble as it's more gummy like 304.

 

[biednick]

I do not know your application so forgive if this sounds dumb; but have you thought about boring it a bit oversized in the 300 series and sleeve it with a tube of a better alloy silver soldered in and ream it to final size with a bore reamer?

That's definitely a possibility, and something I'll look into. I purposely left out the application to avoid the risk of this devolving into a discussion on legality rather than the process of making it. It'll be a 28 gauge AOW made on a form 1.

 

[biednick]

Now that I think about it the easiest option will probably be to buy a 22 cal blank with an appropriate OD, drill it with the piloted 5/16 drill I use for relining barrels, then drill and ream to size. I'll have a good hole to start with and won't need to worry about the rifling pushing my first bit off center.

 

[Smithdoor]

I would be worried about work hardening also. especially if your cutter loses an edge.

You will need to keep a sharp drill bit.
It is a pain to drill deep holes .

You drill little them move tail stock out to clear chips. Then put a lot of cutting oil hole bring stock back lock down and drill little and repeat till done.

Dave

 

[Martin W]

Flood coolant is no problem, but everything I've seen about gun drilling involves what appears to be closer to MQL coolant at several hundred PSI. The equipment to do that is fairly expensive, which is why I'm somewhat adverse to gun drilling.

Yeah I hear you. With a single flute bit, it will jam with chips pretty quick. Hence the high pressure coolant.