drilling a .096 dia into 316 x 3 inch/ not going straight

[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 ?

 

[BillPSU]

Make the hole and turn the OD and face locating on the hole.

 

[ajack1]

I might be stating the obvious here but firstly check that the tailstock is on the true centre, start off (after a centre drill) with a short drill and increase in length, don’t start with a long series, ensure all drills are correctly sharpened, if they are “one sided” this will cause wandering, don’t try and force the feed rate you drill at.

Even with all this I would say you are up against it, could you outsource to a specialist deep drilling company? Failing that drill the hole with sacrificial ends true up between centres.

Good luck.

 

[BillPSU]

You are above a 30 to 1 length to hole diameter. Gundrilling would produce the most accurate hole. If you are using standard twist drills you will see drill walk caused by drill point inaccuracy, drill web inaccuracy and even material variation through the bar. Unless you are producing hundreds of parts drill the part and turn the and face material to the hole.

One trick to improve straightness is to turn the part and the tool.

 

[Rhodrons]

In the past we had to drill a stright hole 2 metres long at 60mm diameter. We found that keeping the drill stationary and turning the 2 metre long part worked extremely effectively. It does not seem immediately obvious why it work but it seems that the system "wants" to drill straight!

 

[Eltron]

I agree with BillPSU. However, I'd suggest you contact your local EDM guys. If you're constantly battling a long skinny hole, they might be able to get it done faster and cheaper. If you slip em a six-pack it might even go faster than that.