Re: Those Cheap Diamond Inserts

On 7/29/2024 11:38 PM, Richard Smith wrote:

I heard diamond
* works for Ali because it has no solubility for Carbon
* does not work for irons/steels because the hard tool "disappears" by
   solution into the iron
?

My apologies.  I didn't at all mean something like a PVD diamond coating.  DCMT is a diamond shaped insert.  Typically your find them coated with TiN, uncoated, and occasionally with TiAlN or AlTiN coatings.  My point was these small geometry inserts that work so well in under power under-rigid machines like the typical import 7-8 by 10-16 mini lathe also work on a heavier machine.  If the big boy inserts don't work these still do.  In this case I was cutting 304 stainless steel. It improved the finish, didn't require sharpening, had less heat input, and did the job much faster net elapsed time.
FYI:  I do a fair amount of aluminum cutting, and generally I've found bright sharp uncoated tools do the best job and have the best material removal rate for me and leave a good finish.  Diamond was popular when I first started cutting aluminum on machine tools, and more recently ZrN has become the popular coating.  I've tried them and the simple fact is a coated tool isn't as sharp.  They might work better for larger tools on larger machines, but on middle weight machines with limited horsepower (5 or less) a bright sharp uncoated tool works best for me. For high speed flood coolant makes the tool last without chip welding, but coatings do not.  On smaller tools horsepower isn't even a factor as the tool can't take it anyway.
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Bob La Londe
CNC Molds N Stuff
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