What would you recommend for speeds, feeds, and DOC to get a smooth surface finish on a ID im doing(currently have a vinyl record finish). after the drill I have .027 inches to bore. I need a 32 micro surface finish
Im using a 1.2inch boring bar with ISCAR WNMG 431 Grade IC8250(.015 nose radius). I cant use a bigger nose radius due to the small chamfer at the end of the ID.
Using a kia turn 15
15 hp spindle
Surface finish is determined by the measured height and width of the surfaces peaks and valleys, similar to measuring a thread. Tool nose radius determines the maximum feedrate allowable to maintain the desired surface finish.
There has been much discussion here recently in other threads on the finer points of a shiny finish vs. measured roughness.
Do you have a Profilometer to check the finish?
32 is roughly equivalent to a 180 grit sandpaper finish.
With a .015" nose radius, you want to be in the .002-.004 FPR range.
A few points for success finishing steels at low DOC.
You need spindle speed to be as high as allowable, I run 1100-1500 SFM for finishing.
DOC wants to be at least the Tool nose radius if possible.
Use Coolant for the least amount of smearing and chip evacuation.
Use a positive finishing chipbreaker.
Here is my go to for steel, it has all of the best characteristics for low DOC passes.
Other manufacturers likely have a good insert as well, just try to find something close to this.
CNMG 431-PF 4325
Here is a demo video of it in action, the video begins with a normal DOC finish pass.
Finishing Steel on a Lathe - YouTube
A .004" DOC pass is then made to bring the mock part to size. (I know this DOC is not recommended for finishing, but it just may save you some grief polishing if you need to sneak up on a tolerance). 1100+ SFM and .017" per side DOC are the recommended minimums, but lower is possible if necessary.