I have had no problem with any steels, and use carbide inserts practically 100%.
I buy industrial inserts and holders, and find that both the triangular and the rhomboid inserts work well, as long as they are positive angle.
The ccmt inserts and holders will work well, and wont have any problems turning steels.
About 6-900 rpm for a bolt, and 0.1 mm - 0.2 mm depth of cut, depending on size and hardness and chips.
Any ebay sellers who sellers any brand carbide inserts work fine, ime.
Of course, I have maybe 300 inserts, for a variety of purposes, and have had good to excellent success with all of them.
I have not experienced this "chinese carbide" problem, myself.
The key is, you MUST use positive insert geometry for a 7x.
And the speeds need to be in the ballpark.
In a busy month, I might use 4-8 inserts, and produce100 litres or 20 kg of tool steel swarf, some of it with the 7x, and some with other tools.
