Speaking of round inserts....

Awl --
It seems to me not of people use these, as I rarely see them in a shop's tool holders/racks.
Seems to me they would offer the most economy ito total cutting edge, and
are geometrically simpler than anything else. And thus would be a mainstay in the job shop.
Do they have a more specific use?
I can tell you one industrial use for them, and big-assed very thick 1+" round inserts (hole in center), at that:
The are used on "wheel-truing" machines in railroad repair shops, to re-face the very heavy wheels on railroad cars. These wheels are deceptively heavy, weighing in at 800+ lbs *each* (no axle, no hardware, just the wheel) on *small* lite-duty railroad cars.
The face of the wheel not only rides on the track (and can wind up with "flats", if the car is dragged along with the hand brakes left on), but is also where the brake pads are applied, which can leave grooves.
I forgot exactly the type of tool used to hold these inserts, but I remember seeing what seemed like hundreds of them mounted. The chips that come off weigh a good part of an ounce, and come off in a blue/black *hailstorm*. wow.... A person in the path of these chips for more than a few seconds could easily be killed, certainly permanently maimed. The noise is beyond deafening, shakes the body.
I *think* the tool that holds these inserts is itself a wheel, mebbe a foot in dia, which is why I seem to remember so many inserts mounted at once. The railroad wheel is slowly turned, while the inserted wheels spins very rapidly, probably moving transverse to the surface an inch or two.
The railroad car wheels are never removed for this process. The whole car (or even a whole multi-car "consist") is brought to special tracks, where a section drops out, exposing the wheels, and the true-ing business then comes up from underneath to start the cutting.
A very very expensive heavy piece of apparatus, all hydraulically moved/operated, except for the motors spinning the tool, which I think are like 25+ hp. The true-ing process itself is actually perty quick, a fraction of the time it takes to actually set the whole thing up.
That's the only time I've seen round inserts used to any great extent.
More than you wanted to know, I'm sure....
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I used to use them for turning.........leaves a super finish and great for spiral chip breaking at high feed.
8mm dia lovely jubbly..........
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Proctologically Violated wrote:

The problem with round inserts for general purpose turning is that they make the widest chip possible for any given depth of cut. That means really, REALLY nasty chips that are difficult to break. To overcome that, you need awesome feedrates, which means you need extremely rigid machines, setups, workpieces, etc. Most folks just say "screw it" and use an 80 degree diamond.
But when the application is just right, round inserts can do amazing things. I once worked with a customer on a challenging turning project. Think of a 10" diameter disc, 2" thick, with about a 2 degree dish running from the OD to almost center. Then put a circle of 8 holes in the face, roughly half way between the center and the OD, and each just over an inch in diameter. Now make it out of a nasty alloy steel, and heat treat it into the mid 50's C scale. Now put a spec on it that says the dish/cone shape has to be right within about a thousandth, and have a 32 max finish.
Grinding this thing would have cost more than you might believe, so we (mostly the customer; but I got to watch and help) tried hard turning with round inserts. 3/4" round inserts, ceramic, on a nice beefy machine (Mori SL6 or 65). It worked perfectly, even across the interruptions where the 1" holes were. It was so much faster and cheaper than grinding, and so much better to have full control of this critical part of the job in house, that the customer got all of the production for this job, which had previously been split up among four shops. He ran bunches of them, and made a LOT of money.
KG
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