Re: Those Cheap Diamond Inserts

On 20/08/2024 19:23, Bob La Londe wrote:

That's true, but I did run across a reference (Stefan Gotteswinter video maybe) to an actual diamond attached to a tool.

PCD diamond turning inserts are actually quite common. They are mostly made from natural diamonds, sometimes synthetic. There is another kind whose name I have forgotten which is even more diamond-y, though still not a single diamond.
PCD inserts (or better CBN ones if machining steels) made for aluminium can be of use to hobby people if careful; being sharper then ones made for harder stuff they will cut with less force, useful on smaller less powerful machines.
Recommended only once you have learned how to use inserts without chipping them!
SPD single point diamond turning tools (which are single diamonds) are often used in CNC machines for optical moulds and lenses. The finish is used as-is, no polishing!!!
Sometimes used for high-accuracy machining of copper and copper alloys too.
When air bearings aren't smooth enough ..
https://www.youtube.com/watch?v=5tQd5RVCriI
I have a 1/2 carat single diamond tool for truing grinding wheels. Cost about £!5 iirc, but that was a while ago. Hmm, still £14.99 on ebay.

There are also coatings  that are called diamond, although most are actually DLC "diamond like coatings."

CVD chemical vapour deposition diamonds are frequently grown on tooling surfaces; they are real diamonds, though not single diamonds when grown on surfaces.
They are sometimes made into blocks in a nickel or cobalt matrix, as found on circular saw blades and polishing disks, though often natural diamonds are cheaper.
Peter Fairbrother