drilling a .096 dia into 316 stainless/ Not going straight 1

[bbbobbb]

I'm trying to drill (in a lathe)a .096 dia into 316 stainless X 3 inches long. I'm having problems with it staying in the center. I would like no more than .010 TIR. Any ideas out their ?

 

[unclesyd]

You are talking about an L/D over thirty. This is very hard to do with a normal drill bit and setup. About the best I've seen with ant consistency is about 10-12 L/D in 316 SS.
As you have probably learned clearing the chips is a major problem. A wedged chip will very easily drive you off line especially with a small diameter drill. When drilling 316 SS stops and starts can also contribute to the wandering problem.
Ever drill company has a bit that is better suited for drilling deep holes. You might check with your supplier.
You might also look at Carpenter Project 70 316 SS for better machineability if the job warrants.

Is this a one off or a many piece job?
What is the total precision required?
Comeback with the above information as there are other possibilities for making the hole.

 

[strokersix]

Try boring with a single point tool as deep as you can first. This will help to guide the drill bit. Make sure your drill bit is accurately sharpened. Use lots of cutting oil and clear chips frequently. Try to always pull a chip and not let the bit slide without cutting because the stainless will tend to work harden. Try resharpening the bit several times for each hole. Is your tailstock on center?

If all the above still isn't straight enough perhaps you can turn the OD between centers after drilling through.

Or visit a shop with an EDM.

 

[MikeHalloran]

For a few holes, I'd start with a stub drill, and finish with a gundrill- style point on an extra- long twist drill.





Mike Halloran
Pembroke Pines, FL, USA