What kind of carbide inserts? What tool holders? what Tool holder holder?
I have found that CNMGs work well on the harder stuff but CCGTs work better on easier stuff (6061).
Nose radius versus movement per rotation makes a difference.
The proper rotational speed makes a difference.
The gumminess of the material makes a big difference.
So many variables.
For a newbie/hobby guy like me, the insert world is a vast and uncertain terrain.
I have some, I like HSS the best.
You'll get it, there is a perfect insert for everything you will ever cut. It's just a matter of finding the right one for the material and SFPM.
Listen to these smart guys.
Place the tool close to center (+- .010") being exactly on center is less important then many imply unless parting to 0.000 in X
Aside from parting to 0.000 I set tool height with a 1/16" reading ruler from the lathe ways, this has never failed me.
Choose an insert for the material that you are turning and the speed at which you need to produce the parts on time.
Turn the stock at the speeds recommended by the insert manufacturer. If they last increase it.
Feed at the rate suggested by the manufacturer. If they last increase it.
All inserts will have suggested SFM, DOC and feed rates printed on the packaging so start there and adjust either up or down.
If you are not turning the part fast enough or have a wobbly machine your results will tend to be poor, wick it up and have at it.
I think being on centre is quite important to get the proper shear on the tool. In lesser materials you may get away with being off centre but parting could turn in to a bad day real fast . Parting is one operation where all conditions should be met. It could take out not just your cutting tool but a whole lot more. Being off centre here with the power feed on could be disaster. Tool decides to rub and does not cut as being fed. Now climbs material then digs in and crash there goes your tool at the least. I d start parting with no power feed until you are confident in your tooling. Pay lots of respect to parting! Usually half your speed and even lower at times.