Proper Lathe Technique

[RHT]

Need to ask you experienced machinist which method produces the best results or does it matter.

When writing gcode to turn stock to a specified depth which, for example, will take 3 passes at a full cut and then there is a small amount needed to cut to a final dimension. Should you take the partial amount first and then the full passes or full passes and then the partial? Work hardening issues?

TIA

RT

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[awerby]

Usually, you'd take the heavy cuts first, and then a light one as a finishing pass. But if the material has work-hardening issues, like some stainless alloys, then it may need a heavy cut to get under the work-hardened layer instead of just rubbing on the surface.

[Zorbit]

Sometimes a light finishing cut doesn't leave a good finish - especially with carbide tooling on stainless steel. Under a magnifying glass you can see rough patches interspersed with bright shiny patches. Carbide tools are often not very sharp, and don't like a shallow cut. I have also learned that when using soluble oil flood coolant, increasing the oil concentration from the minimal 7% to 15% gives a better finish, noticeably on 303 stainless.