You've opened a can of worms when you start looking at carbide inserts, especially for threading.
Personally, I use Sandvik inserts and toolholders for threading (and turning, too). Yes, there are inserts for internal threading.
This may turn out to be a lot more expensive than you realize, as you will need a variety of sizes for cutting different threads, plus you need the toolholders as well.
You could just buy some nice carbide threading bars, say from ThinBit or Micro 100, and just resharpen them as needed, or just buy new ones as they wear out.
But, if you want to go inserts and toolholders, I would suggest calling your local Sandvik reseller and ask for a copy of their Main Catalog. That will cover just about anything that you might need. Or, if you are doing mainly small pieces, then check out
Sandvik online, under Small Part Machining. Download their files, read them all, then ask questions.
While Sandvik carbide threading inserts seem expensive, the ones that I use have three points on each piece, so if divided by three, the cost isn't that bad.
I must say that they wear exceptionally well.
I find that I'm mainly only making two or three sizes of threads nowadays, so I overbought initially. Think carefully about what thread sizes you are likely to use the most, then order a few inserts for those threads. You can always buy more later.
eBay is often a good source for Sandvik threading inserts.
As for cut knurling, that requires a special toolholder also, one that holds two carbide knurling wheels. And of course, there a wide variety of pitches to choose from there also. Visit the websites for
IFanger,
Zeus,
Quick,
Dorian, and
Accu Track. They all have a wealth of info for download.
