Superfinishing
Stone and tape finishing for functional surface texture, with incoming geometry, stock allowance and inspection boundaries.
Tags: processes, finishing, abrasive-machining
On this page
An example 30.010 mm journal with 3–5 µm radial removal per side finishes at 30.000–30.004 mm. The low outcome misses an assumed 30.001 mm minimum even if texture passes. Check size, texture and any functional coating remaining after finishing.
Process and intended result
Short oscillation and workpiece rotation generate intersecting abrasive paths. Supfina describes grooves for lubricant distribution and plateaux for contact. Specify the abrasive stone or tape and functional texture. Supfina superfinishing technology
Names overlap. ATLANTIC calls its bearing-race process short-stroke honing or superfinishing; Thielenhaus uses Microfinish/Superfinish for its technology. Specify the actual surface, tooling and movement rather than assuming the name defines an interchangeable machine cycle. ATLANTIC also identifies external shafts and rollers as applications of short-stroke oscillating stone attachments. ATLANTIC short-stroke honing, Thielenhaus technology
Functional texture and geometry are separate requirements
The objective depends on the component: a bearing race, seal land and lubricated journal need different evidence. Thielenhaus discusses removal of roughness peaks together with application-specific roughness and shape requirements. A lower average roughness is not by itself proof of lower leakage, longer fatigue life or the required lubricant behavior. Qualify those functions for the actual material pair, load, lubricant and operating conditions. Thielenhaus application and geometry guidance
Supfina lists improvements in roundness, waviness and cylindricity among potential benefits. That does not mean every tape or stone setup corrects an arbitrary incoming form error. Establish the stock available, tool contact, support arrangement and demonstrated correction for the actual part. A texture measurement on one trace cannot certify diameter, roundness or cylindricity. Supfina capability description
| Requirement | Useful information to specify |
|---|---|
| Final size and fit | Diameter or other size limits, allowance, measurement temperature and applicable decision rule |
| Form and alignment | Roundness, cylindricity, straightness or face relationship, with locations and datum references |
| Surface texture | Named parameters, units, lay, measurement direction and controlled evaluation method |
| Local defects | Scratch, chatter, edge and transition requirements on significant surfaces |
| Functional result | Relevant bearing, sealing, friction or durability test with the actual service conditions |
Tool selection and incoming condition
A stone designation includes more than nominal grit. Thielenhaus's Microfinish Abrasive Tools guide distinguishes abrasive, grain size, hardness, structure, bond and treatment. Its hardness discussion concerns grain retention by the bond; it should not be confused with the hardness of the workpiece. Film-backed abrasives have their own grain, backing and contact arrangements. Do not substitute one tool solely because its label contains the same grit number. Thielenhaus tool guide, printed pages 3–5 and 8–9
Record incoming material, hardness/heat treatment, coating condition, size, form and texture. The same guide recommends establishing incoming quality and a measurement baseline before trials, then comparing part quality, removal, tool life, production rate and fluid conditions. A change in upstream grinding or coolant is therefore a reason to reassess the process, even when the drawing's final roughness value is unchanged. Thielenhaus tool trials, printed page 10
The guide's troubleshooting table connects results to tool selection, incoming quality, concentricity, coolant, pressure and motion. These are interacting variables, not a universal adjustment recipe. Diagnose scratches, chatter, excessive heat or inconsistent removal against the actual setup; changing only to a finer abrasive can leave the underlying problem unresolved. Thielenhaus troubleshooting, printed page 11
Allowance and original dimensional example
ATLANTIC's bearing-race example distinguishes a pre-finishing allowance from a smaller final-finishing removal, with values depending on the application. This supports planning stages separately; it does not establish a stock allowance for another ring, shaft or coating. Agree whether quoted removal is radial, diametral, normal to a surface or a machine-specific quantity before calculating a final dimension. ATLANTIC bearing-race example
Original illustrative example: assume a cylindrical journal enters at 30.010 mm diameter. Assume uniform radial removal of 3–5 µm per side, with no other dimensional change:
final diameter = 30.010 mm − 2 × radial removal.
The hypothetical drawing interval is 30.001–30.005 mm. Apply the specified decision rule and measurement uncertainty to actual size.
For a coated component, separately establish the coating remaining after finishing and the permitted local removal. A satisfactory final size cannot prove that the functional layer remains intact at every edge or high spot.
Surface-texture inspection
ISO 21920-2:2021, edition 1, December 2021, corrected June 2022, specifies terms, definitions and parameters for profile surface texture. Its public record lists the earlier ISO 4287 and ISO 13565-2 among withdrawn predecessors and identifies a replacement project under development. Keep the contractual parameter definitions and evaluation method explicit; the project does not itself replace the published edition. The public scope supplies neither a universal superfinishing limit nor an automatic conversion between legacy and current inspection results. ISO 21920-2 record
A mean value loses information. As a mathematical illustration, consider two idealized, equally weighted, zero-mean height arrays in micrometres: [1, −1, 1, −1] and [2, 0, −2, 0]. Both have mean absolute height 1 µm, but their maximum-to-minimum ranges are 2 µm and 4 µm. This is not a standards-compliant roughness evaluation: filtering, sampling and instrument response are deliberately omitted. It shows why a single average cannot uniquely describe a surface's peaks, valleys or spacing.
Select additional texture information according to function. Record trace direction, locations, filtering/evaluation settings, instrument suitability and the surface's cleaned condition. Inspect form and local defects separately. Do not report an optical appearance judgment as a measured roughness result.
Production handoff
Provide the drawing revision, substrate and coating condition, significant surfaces, incoming limits, final size/form/texture requirements, permitted transitions and edge changes, and the approved finishing route. Preserve tool identity, movement/contact setup, fluid controls, inspection locations and the relationship between representative samples and production parts. Agree cleaning and handling after finishing so abrasive residue or later damage does not invalidate an otherwise acceptable surface.
The supplier web pages cited here have no verified technical issue date. The Thielenhaus guide carries the printed code 0424_EN on its back page; no more precise issue date is inferred. Its examples and the original calculations above are distinguished from contractual process requirements.