Precision Grinding Service
Resolute Precision Manufacturing coordinates precision grinding OD grinding, ID grinding, surface grinding, and centerless grinding for machined components requiring final dimensional accuracy and surface finish beyond what turning or milling alone can achieve. We manage the complete process from machining through grinding and deliver fully finished parts with inspection documentation from a single purchase order. Request a QuoteWhy Grinding Follows Machining
CNC turning and milling produce excellent dimensional accuracy but there are applications where the requirements push beyond what cutting tools alone can achieve. Bearing journals requiring Ra 16 microinch or better surface finish. Hardened shafts that distorted slightly during quench and must be returned to roundness and size. Gage surfaces requiring tolerances of ±0.0002 inch or tighter. Flat reference surfaces requiring flatness of less than 0.0001 inch per inch.
For these applications, precision grinding follows machining and heat treatment as the final material removal step removing a small amount of material with an abrasive wheel to achieve the dimensional accuracy, roundness, cylindricity, and surface finish that the application requires.
Grinding Processes We Coordinate
We coordinate four grinding process types depending on part geometry and requirement:
OD cylindrical grinding — removes material from the outside diameter of a rotating part; achieves dimensional tolerance of ±0.0001″ and Ra 8 or better on shaft ODs, bearing journals, and cylindrical sealing surfaces
ID grinding — removes material from an internal bore; achieves tight bore size, roundness, and surface finish for bearing housings, valve bores, and precision ID features
Surface grinding — removes material from a flat surface using a rotating abrasive wheel; achieves flatness, parallelism, and perpendicular to ±0.0002″ and Ra 16 or better on reference surfaces and mating faces
Centreless grinding — cylindrical OD grinding without centres; high-throughput process for shafts and pins requiring tight OD tolerance and finish in production quantities
Specifications
| OD Grinding | Diameter tolerance: ±0.0001″; roundness: 0.0001″ TIR; surface finish: Ra 8 or better |
| ID Grinding | Bore tolerance: ±0.0002″; roundness: 0.0001″; surface finish: Ra 16 or better |
| Surface Grinding | Flatness: 0.0001″ per inch; parallelism: 0.0002″; surface finish: Ra 16 or better |
| Centerless Grinding | OD tolerance: ±0.0002″; roundness: 0.0001″; high-throughput production grinding |
| Materials | All machinable metals, including hardened steels up to Rc 65, carbide, stainless steel, aluminum, and titanium |
| Stock Removal | Typically 0.003″–0.010″ stock removal; machining allowance should be included in the part design |
| Documentation | Dimensional inspection reports provided with ground parts; Ra surface finish measurements available for critical features |
| ISO | ISO 9001:2015; outside suppliers qualified under RPM’s approved vendor procedures |
Designing for Grinding
To achieve final ground dimensions, parts must be machined with a grinding stock allowance on the surfaces to be ground. Our engineers advise on appropriate stock allowances during quoting. General guidelines:
OD grinding after turning: leave 0.003″ to 0.010″ stock on diameter (0.0015″ to 0.005″ per side)
OD grinding after heat treat and quench: leave 0.005″ to 0.015″ stock to allow for distortion removal
Surface grinding: leave 0.005″ to 0.010″ stock on the face to be ground
ID grinding: leave 0.003″ to 0.008″ stock on the bore diameter
Always specify the final ground dimension on the drawing — not the pre-grind machined dimension
Frequently Asked Questions
What surface finish does OD cylindrical grinding achieve?
OD cylindrical grinding typically achieves Ra 8–16 microinch in standard conditions, and Ra 4 or better with fine-grit wheel and spark-out passes. This is required for bearing journals, hydraulic cylinder rods, and precision sealing surfaces.
Can RPM coordinate grinding of hardened parts?
Yes. Grinding is specifically designed for hardened material it is the standard method for bringing heat-treated shafts to final size and surface finish. We coordinate machining, heat treating, and grinding as a complete sequence and deliver the finished part with all process certifications.
How much stock should I leave for grinding?
As a general rule, leave 0.005″ total stock (0.0025″ per side) on OD features to be ground after turning only. After quench heat treatment, increase this to 0.010″ to 0.015″ total to accommodate distortion. We specify the exact stock allowance recommendation on your quote.
Is surface grinding the same as lapping or honing?
No. Surface grinding removes material with an abrasive wheel mounted on a rotating spindle. Lapping uses a flat lap plate with abrasive slurry for ultra-flat surfaces. Honing uses abrasive stones in a bore for internal surface finish. Each process achieves different surface characteristics contact us to discuss which is appropriate for your application.