mill boring bar material to remove

[So not a Guru]

We have to bore a couple 0.5322" - 0.5324" holes in a 6Al-4V part. We have a very good adjustable boring system.

I'm wondering what starting hole diameter would be recommended?

[nickbe10]

32 minutes ago, So not a Guru said:

I'm wondering what starting hole diameter would be recommended?

Ti is pretty tough so you might need to leave a little more stock than with say 15-5 to make sure you get a good chip.

Depending how big an insert and bar you can cram in there I wouldn't hesitate to start at .01 stock (per side) and check the results.

What quality Ti do they lumber you with? That can make a difference too.

[So not a Guru]

25 minutes ago, nickbe10 said:

Ti is pretty tough so you might need to leave a little more stock than with say 15-5 to make sure you get a good chip.

Depending how big an insert and bar you can cram in there I wouldn't hesitate to start at .01 stock (per side) and check the results.

What quality Ti do they lumber you with? That can make a difference too.

Ti CP 40KSI AMS4902, it cuts pretty well and doesn't distort much.

[Rstewart]

± .0001 bore?  Sounds like that will be hard to control with a boring bar in Ti.  

[crazy^millman]

I would roller burnish or have it jig ground.

[So not a Guru]

12 hours ago, crazy^millman said:

I would roller burnish or have it jig ground.

Like this?

https://cogsdill.com/brochures/sr-series-roll-finish/

 

[Leon82]

I usually leave .001 per side.

 

Solid bars sometimes I have to spring it a few or 20 times. Inserted bars usually run better.

 

Once the size is set and the hole comes out with a taper you just keep springing it because if you open it up when if finally cuts it will be oversized.

We've bored slots in titanium too. 

Once it's dialed in I may open up the pilot hole closer to finish also

[crazy^millman]

7 hours ago, So not a Guru said:

Like this?

https://cogsdill.com/brochures/sr-series-roll-finish/

 

Yes leave about .0003 to .0006 with a carbide reamer. You can dial it in pretty good. Need to watch not to good a finish. I have had 8um and hit a 2um and the parts were rejected for being to smooth and not allowing the seal at -356F degrees to seal correctly. They had to change the print requirements on all parts after that to say 4um to 8um finish required.