Cant help you on thread milling as I dont thread mill.
However your lathe issues are not the insert nor the metal its the programming for that style insert.
316 cuts like butter you just need to apply the right info to the type oif material.
you should be roughing with a cnmg or trigon 4 series and finsihing with that or a ccmt. I liek the ccmt but wont waste my time roughing with it in the docs you got especially facing.
Your facing is way to aggressive for a ccmt. your more than likely damaging your inserts when you get to the last .150 dia of the facing op especially at the docs you have,
you didnt say what nose rad you were using either. for facing with a ccmt requiers a little more finess.
I use 350-400 sfm on cutting 316 od feed runs between .006-.008 I use pretty much only sandvick.
rough faceing wnmg or cnmg 432 nor more than .050 doc at .004-.005 then once I hit .200 dia I slow it up to .001-.002 feed. this also highly depends on what your max rpm speed is set at. If I want to hog off the faces I use a SNMG or CNMG 432-434 with a holder that holds the insert at 90º
roughing o.d. 350-400 SFM doc .050-.100 depending on how big the dia of the part is .006-.008 feed depending on the tool nose rad as well.
Generally you should use a 432 min for roughing as you can turn a tad faster in feed rates and DOC.
after your done roughing take that same tool and face any faces past the Z 0 face too with in .003 size. its better to start from the largest o.d. and run a few thou from the smaller o.d.
finishing Separate tool cnmg wnmg or ccmt with with a rad that you can use and interpulate fillet rads. DONT Plunge into them thats dumb and blows inserts and gives you a crappy fillet.
I leave .003 on the faces for all finish passes(see above) and .010 for o.d.
again biggest nose rad the better that you can still interpolate any fillet rads with.
as far as your bore ccmt works great if you have one small enough to clear your bore. if not solid carbide b-bars by internal tool and other manufacturers work fantastic, doc you need to be light on small bores as well as SFM sometimes by 50%.
What ever you do dont ask your customer what grade his 316 is, where it came from or can he change it cause its too hard for you to cut Cause its not and you will look like a fool in doing so on 316 or 304 stainless.
Dont know what type of machine you got you said 2 chucks so I assume its a decent machine you shouldnt have any issues as I can cut the stuff on my little Miyano all day long with no issues just like I can on my 10″ chuck machines just lighter cuts on the Miyano.
Just remember its just another “COMMON” Material that gets cut every single days by tons of shops with NO PROBLEMS.