First off I'm going to recommend running a larger drill, around 1.250+ if possible to give you more room to work with a 1" boring bar. Technically you could put one in now making sure that the first pass is deep enough to clear the min bore spec of the bar, but then you are making pretty wide chips with little room to remove them. I'm sure you are well acquainted at this point with the joys of chip evacuation when boring 304. Also 550SFM is too much for rough boring 304 with carbide, knock it down to 350SFM for now then try gradually increasing later if necessary after you have a reliable process nailed down.
Next, here are the guides to the nomenclature for ANSI/ISO standard inserts and boring bars.
Insert Designation Chart - provides ANSI and ISO designation code definitions for carbide insert shapes, relief angles, tolerances, chipbreaker codes, hole types, size values, thickness values, radius values, wiper lead angle, wiper clearance angle,
Boring Bar ANSI Designation Chart - provides ANSI and ISO designation code definitions for the boring bar material, diameter, length, insert holding type, insert shape, boring bar style, insert relief angle, direction, insert inscribed circle (IC)
There's a lot there to take in, just keep them handy and reference specific things as you come across them. In time you will start to remember the codes by heart and not have to look up everything. Know that some manufacturers use variations of the codes that are basically the same thing but just different enough that google won't find it right away. A few (Hertel comes to mind) sometimes use a totally proprietary naming system for products that are actually standard and interchangeable with other makes.
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What I'm going to recommend first is a 7 degree positive insert ("C" relief angle), either "C" shape (80 degree diamond) or "S" shape (square).
If you need this tool to machine the bottom face of the hole you need a negative end cutting angle, like the following:
3 .48mm Min Bore Diam, 1" Shank Diam, 12" 62181631 - MSC
If you need to get close to the bottom face but can finish with another tool you can use a neutral end cutting angle, like the following:
3 .48mm Min Bore Diam, 1" Shank Diam, 12" 86461894 - MSC
If it is acceptable to use something that can't get near the corner (it looks like your problem interruption hole doesn't go all the way down the bore so this may be a good option in tandem with another bar) you can use a positive end cutting angle with a square insert. These are kinda rare in positive insert geometries but they are around:
S16R SSKCR4 – Ultra-Dex USA
Those 3 are in order from weakest to strongest out at the corner doing the cutting. It's also possible to use the 100 degree corner of the C shape inserts for positive end angle cutting which is even stronger than the square inserts, but I can't find off the shelf boring bars for positive inserts that accommodate it.
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For inserts what you need is a very tough grade with a large radius to survive the interruption. I'll make some specific recommendations for the 80 degree diamond insert bars I listed earlier:
Sumitomo CCMT32.52 ESU Grade AC6040M
https://www.mscdirect.com/product/details/59143065
Sumitomo CCMT32.52 ESU Grade AC530U
https://www.mscdirect.com/product/details/53983318
Start around 0.050" depth of cut and work up, that ESU breaker geometry is suitable for up to around 3 times that if the rest of your setup can handle it. My lathe isn't terribly rigid and I use mostly small bars so my experience is mostly on the lower end of that. I find these work well around 0.009" feed in a continuous cut for 304, but with your severe interruption you may need to run less to keep breakage under control.
If you can't get Sumitomo for some reason the following from Kennametal should be suitable. I haven't used this exact grade but I have used some of the harder inserts from this same range with good results.
Kennametal CCMT32.52 LF Grade KCM35
https://www.mscdirect.com/product/details/08342727
Kennametal CCMT32.52 MF Grade KCM35
https://www.mscdirect.com/product/details/08342743
Difference between them is the breaker, LF is for smaller cuts than MF.
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You can also use 11 degree positive inserts ("P" relief angle) with mostly similar results for boring. Reason being the angle that the bar holds the insert. In the case we are looking at, a 1" bar for a CPMT32.52 will typically hold the insert perfectly level, for 11 degrees relief total. A 1" bar for a CCMT32.52 will hold the insert tilted down 4 degrees, which also comes out to 11 degrees total when added to the 7 degrees built into the insert.
Based on this, I generally use "C" inserts because of much wider insert availability (seems a lot of manufacturers have come to the same conclusion) and because they are more suitable to use for OD turning when needed.
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You are going to get a lot of recommendations for using CNMG inserts, which is certainly an option but not one I like in this size range. If you look at the following:
https://www.kennametal.com/en/produ...071/63840673/64022655/64022665/100001227.html
Look for A16TMCLNR4 under the catalog number heading then over to the γF° field. You'll see that they had to make the insert seat 14 degrees negative to fit it in that hole. This means that unless you get a high positive special finishing insert (that probably won't survive the interruption) with tons of top rake, you will actually end up with a negative, or at best neutral cutting action which doesn't work well at all in 304.
Furthermore, the insert and seat rising at that high angle behind the cutting edge as well as the top clamp both get in the way of chip flow.
In short I think that negative inserts in boring applications are best reserved for larger holes than we are dealing with here.
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Note that I linked a bunch of stuff from MSC for convenience, but my actual recommendation at least longer term is to get in touch with some local distributors and have them send you the full catalogs from a few brands that they represent. Get used to finding things that way, cutting tool makers are generally old school and still haven't really figured out how to get their stuff into robust, intuitive electronic interfaces. This is getting better lately but there's still a long ways to go.
If you find any specific items you are considering ordering feel free to send me the relevant part numbers and I'll do a sanity check to confirm compatibility and such.