Internal Retaining Ring Groove Tool

If not large quantities why not grind a HSS or carbide bit to suit a boring bar which can hold a bit at 90 degrees to the bar axis. I have a number of bits for such tasks for internal threading or grooving. This type of thing

boring bar with square (cut-off) blade

I can just grab a piece of tool steel and go stand in front of the grinder for a while, but I was wondering if there is a simple elegant, not over priced tool to do the job. Ring groove will likely be 1.1" give or take.

Now about face trepanning a recess that butts up against a shank diameter. For now I have been using a hand ground brazed carbide inside threading tool. It no longer looks like a theading tool and has relief on one side for the smallest diameter of the recessed area.

I use a worn surface grinder I bought for $100 to grind lathe bits to close angular and dimensional tolerance, after roughing them with an angle grinder and then a bench grinder.

If your toolpost will swivel to it, 45 degrees is a good tool bit angle for custom inside corner tools, ground into the end of the bit. For that tool grind the end slightly less than 45 degrees for side relief and grind a vee notch to form the outer cutting edge, then relieve for circular clearance. I have a Multifix that indexes in 9 degree steps.

The QCTP on the PM1440 free spins so I can set it at any angle. I can see how turning it would work with the 45 degree bar. The lathe bit would have to stick out a little more, but it would work.

I've been playing with the idea of CNC roughing the part on the mill, and then just throwing it in the lathe to finish. Maybe leave the OD 10 thou over, and the ID 10 thou under on the two dimensions that need to be pretty concentric and just finish those on the lathe.

If it were for a big bore cylinder, I'd consider a slitting saw blade with suitable width, even if it were broken (just choose a good tooth, and take aim). Hand-sharpening a square cutter for a composite boring bar could work, but it's not something where I can really see the cut, so if I sharpen it wrong... how would I ever be able to correct it?

The lathe dial gives you the depth of the groove and these can measure its width and position:

I use the appropriate hole in a drill bit gauge or a washer to show when I've hand ground enough circular relief below the cutting edge.