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Drilling 316L SS .125"D x 3"lg (24xD)


Feb 17, 2023
Houston, TX
I have a job coming up that is going to require drilling a .125" hole 3" dp in .75" OD 316L stainless on a CNC lathe with y-axis and live tooling. I plan on using a Nachi carbide 25D drill with thru coolant along with the recommended pilot drill in er collet holders. From what I've researched it seems like the best way to go is to run the pilot drill with a static tool and the deep drill with both spindles turning (main spindle 1/3 of the rpm's and live spindle 2/3). Does this sound like the best approach or do I have no business running this on a non specialized drilling machine? Also should I spot drill before the pilot? Btw I planned on using the polygonal turning function to get both spindles counter rotating.
You can spot before the pilot. Just make sure the pilot is a slip fit for the main drill. And you enter slowly. I like to enter with an M04 and flood coolant, then M03 and thru coolant before spinning up the rpm's.
Also what kind of coolant psi do you have on that machine?
As for syncing the spindles, I can't answer that one.
Yes the pilot drill will be at .126. Thanks for the entering slow with M04 tip, I'll try that although I don't think I can switch from flood to thru coolant. I was just going to use thru coolant with a sealed collet. I think the coolant pressure is around 140 psi.
You might want to check with Nachi. Don't think 125 psi is gonna be enough.

Sounds like a tough job. Good luck.
Thanks for the heads up. I looked back through the catalog and you’re right. The minimum recommended pressure is 300psi… gonna look into getting the upgrade. It’s probably well worth it.
I've had giod results with Nachi and Mikron.

You have a tiger by the tail. If you haven't call manufacturers tech line, don't go through your vendor. If they say their stuff will work you may be able to get it on a trial basis. If it don't work you don't pay. Be prepared to have a salesman looking over your shoulder when you try it out.
My vote would be crazydrill from Mikron and drive it with the live tool only. 150psi coolant probably isn't going to cut it however, if you can upgrade to 300psi that would be better. 1000psi would be best, a lot of lathes have that as an option now.
I've always ran the drills/spindles at 50/50, but I doubt that 30/70 will be a problem ...

I like that idea of M4'ing into the hole....
That's interesting...
I usually just go in at low RPM, but ....

I have had good luck (VERY predictable life - exactly what Titex said to expect!) in this app with Titex A6685TFP drills.


Think Snow Eh!