Before

Raw CNC-machined stainless steel ball showing visible tool paths before polishing.

3D surface roughness scan of CNC-machined stainless steel ball showing high Ra values and surface peaks.

After

Polished stainless steel ball with uniform mirror surface finish after Bel Air precision polishing process.

3D surface roughness scan after polishing showing reduced Ra and improved surface smoothness.

Objective

Achieve a consistently smooth, low-roughness surface finish on CNC-machined 13-8 stainless steel balls used in aerospace applications. The target specification was a surface finish of ≤6 Ra, requiring removal of machining lines while maintaining dimensional accuracy and spherical geometry.

IndustryAerospace/Defense
Part DescriptionBall
Fabrication Method CNC Machined
Material13-8 Stainless Steel, Condition H950 (45-50 HRC)
Process TechnologyMultiple Methods, Polishing
Equipment TypeCentrifugal Barrel Finisher/Harperizer, Centrifugal Disc Finisher, Vibratory Finisher

Solution

Bel Air developed a high-precision polishing process to reduce surface roughness on CNC-machined 13-8 stainless steel balls to ≤6 Ra. Multiple finishing platforms were evaluated, and the Centrifugal Disc Finisher proved to be the most effective primary step due to its ability to uniformly polish spherical surfaces.

A controlled media refinement approach was used to remove machining lines and produce a smooth, reflective finish without altering the ball’s diameter or form. Surface metrology confirmed final finish performance.

This process ensured:

  • Sub-6 Ra finish, validated through surface measurement
  • No distortion of spherical geometry
  • A repeatable, production-ready polishing workflow

If you are unsure what equipment and media you require to achieve your desired surface finish, then send us your part, and we will evaluate it and provide you with a metrology report.