If you are fan of YouTube machining videos MrPete222 (tubalcain) you may have seen an insert tool he seems to like a lot for basic grunt turning. It?s a doubled ended tool with a triangular insert on each end.
I've looked for one, but haven't found one. I considered getting a pair of MTENN insert tools, and cutting them to fit in one of my tool holders back to back, but they hold the insert at an angle. That's fine except for threading. I don't know if the ten degree added angle throws off the 60 degree angle enough to matter, but it throws it off enough that I'd still feel more comfortable swapping to a threading tool or a threading insert.
Anyway, I'd really like to find a tool like the one he is using.
I use one regularly. It is made by Aloris. There are two models of it the 16 or the 16N -- each prefixed by AXA, BXA, CXA or whatever for the size you need. The difference is that the 'N' type has the inserts tilted for negative rake inserts, (and with a chipbreaker groove in the insert, it has an effective positive rake for normal cuts). If you use an insert without the chipbreaker groove, you get true negative rake behavior, which means that you need a fast and high torque lathe. However, with the chipbreaker grooves, you don't need that much, though rigid is beneficial at all times.
One benefit of the negative rake with the chipbreaker groove is that if you don't crash the tip, you get six cutting edges per insert, three on one side and three more on the other side.
I've seen some clone companies show up on eBay which have something which looks like that, but the edge is not parallel to the tool holder, and I think that you can't get the negative rake version of that.
You don't want to use normal triangular inserts for threading. The tip is rounded too much (three degrees of rounding for normal ones), and it does not have proper clearance for the cut on each side, tilt it one way and the other side has negative clearance. There are special inserts and holders made for thread cutting -- with general purpose inserts, covering a range of pitches, and ones which cut full form of a single thread. The inserts look something like this from the top (if you view with a fixed pitch font, not a proportional pitch one.) Courier is a good choice for a fixed pitch font:
^_____ \ > \ () / \ / < /
Each of the points has an angle built in for the most common thread pitches. If you need a particularly coarse or fine thread, there are replacement anvils which tilt the insert in 0.5 degree increments to adjust for the proper thread pitch angle. ISCAR is one of the makers for these inserts and holders.
Go to someplace which sells Aloris toolposts (like MSC) and search for the ?XA-16 or ?XA-16N -- and be sitting down when you read the price. (The '?' is replaced with 'A', 'B', or 'C', depending on the size of the toolpost.) You can search eBay too, but my own experience shows that the used holders for the ?XA-16(n) holders have prices not that much below the new ones from MSC, so I spent the money for new holders.
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