Re: Machinning titanium!
Reduce your depth of cut and up the feed, adjust speed to where you can get 0.020"-0.030" feed rate assuming you have the HP to get there. I would forget about using coolant as you can crack the inserts from the extreme temps, the idea is to remove the heat in the chip not with coolant. Use coolant behind the tool to cool the material behind to reduce the heat buildup with every pass. Before you do any finishing unchuck and let them cool overnight, figure on doing all the roughing first and the finishing last with cooling periods inbetween...it has to be room temp to do the finishing with a smear of cutting oil like you would use with a pipe threader (sulphurized oil), its going to smoke so get the vents going in the shop or use a smoke eater. Oil leaves the nicest finish but if the Ra is not important water soluble coolant is OK, whatever you do don't tickle the material with low feeds, it will just harden up on you with every pass.
However there is nothing that you can do about the notch wear your going to get on the insert from the hard skin left after every cut, what I used to do was get three different feed rates and depths dialed in and then start with the deepest cut depth/feed rate and work out so the notch line moves out on the tool insert.
No matter what you do your going to have to watch the insert for the first signs of notch wear from the hard skin, as soon as you see it change the tool or reduce the depth of cut. You going to go through a pile of inserts no matter what you do.
You haven't mentioned the type or grade of Titanium but for the most part all the grades machine like 316L-SS except for the really soft gummy stuff like Grade 1 or 2 which should be similar to 304 SS to machine. God help you if these blanks are alloyed 442 or any of the 6 series grades...they make my freakin eye twitch.
Sounds like these are rough blanks your turning so getting under the skin to where the blank is at least round might be where your having trouble, there is really no easy solution except to use negative rake tooling until the blank is round with no chip land and use fast feeds and shallow cuts...that scale is murder on forged blanks...rotate the tool insert every pass if you have too and use cheap uncoated inserts since it isn't going to matter what you use to get her round...they are going to break and snap and chip and pop, go slow.
Hope you have decent tooling (I recommend Sandvik Coromant) most shops use the cheap Iscar or Seco stuff and their inserts are just not ideal for these kind of materials, its been awhile since I have been in the business so things may have changed but their stuff used to be crap for alloyed SS or TI. Sandvik has some engineered stuff and well trained techs in my area who were great for offering advice on their tooling choices available, they saved me a ton of hassle by just giving them a call and getting advice on which of their products to use, they made stuff that other mfgs just couldn't touch for durability and output...smart machinists in that company.
Good luck dude and don't let her vibrate, if you hear a whistle back off the feed...it will snap in no time flat if you don't. Hopefully you have a good machine to do this on, if the headstock bearings have some play it will be a b!tch to do.
