# Honing

Planning abrasive bore finishing with separate requirements for size, form, surface texture, access and inspection.

Reviewed: 2026-11-01

Tags: processes, finishing, honing, bore-finishing

An ideal **50 mm bore at 120 rpm** gives **0.31416 m/s** circumferential speed. With **0.100 m/s** axial speed in both directions, the acute included crosshatch angle is **35.31°**. State the angle convention and measure bore form, texture and size independently.

## Process and scope

Sunnen distinguishes bore cylindricity from texture and notes that some honing operations remove appreciable stock. Specify geometry, texture and allowance separately. [Sunnen honing overview](https://www.sunnen.com/pages/educational-information)

Define the incoming bore and required result. A bore that looks crosshatched is not thereby demonstrated correct in diameter, taper, roundness, straightness, location or texture. Likewise, a satisfactory size reading does not establish the full cylindrical form or the functional surface profile.

## Geometry and texture are separate requirements

A useful specification identifies the final size limits, geometric requirements, controlled length and surface-texture definition. Resolve whether location relative to other features also needs control; do not assume that a bore-finishing operation automatically relocates an incorrectly positioned hole.

Sunnen's **Data File 104, Obtaining Specified Finishes by Honing**, discusses grit, material and tooling effects on finish, and describes multi-stage work where stock removal and fine finish demand different tooling stages. Its approximate finish examples are not guaranteed capabilities for every alloy or machine. [Sunnen DF104](https://cdn.shopify.com/s/files/1/0903/7856/7977/files/DF104_c_200903.pdf?v=1756913584)

Plateau and other specialized honing routes also require a defined functional surface. Gehring's formhoning discussion distinguishes producing the nominal shape from the subsequent roughness-profile operation, and describes checking parameters such as **Rpk, Rk and Rvk** for its plateau structures. These are a named development example, not a universal parameter set for every honed bearing or cylinder. [Gehring formhoning and plateau profiles](https://gehring-group.com/en/honing/technology/formhoning/)

Do not replace a multi-parameter profile requirement with a generic Ra limit or a visual pattern. Preserve the governing texture standard, filtering, evaluation lengths, trace direction and acceptance rule where relevant. The required functional profile should determine inspection, rather than whichever roughness value the instrument displays by default.

## Tooling, access and support

Identify bore material/hardness, starting form, stock allowance, length/diameter, interruptions, blind end and any relief. Select the abrasive, bond, tool construction, fluid and machine together for that application. Qualify the route with representative incoming parts rather than assuming the same abrasive designation produces the same result in every material.

Sunnen's **Data File 103, Honing Blind Holes**, explains why a blind bore differs from an open-through bore: front-end tool wear, stability, bottom access and truing require particular attention. Its examples describe specified mandrel/tool arrangements. Do not copy its illustrated tooling alterations into an unrelated tool or machine without the manufacturer's applicable instructions. [Sunnen DF103](https://cdn.shopify.com/s/files/1/0903/7856/7977/files/DF103_c_200903.pdf?v=1756913583)

Record the accessible and controlled length. A tool that cannot reach the bottom region cannot demonstrate that region was finished merely because the entry diameter is correct. Review thin walls, clamping and support because distortion during processing or measurement can change the apparent bore geometry.

## Crosshatch and motion

In conventional rotating/reciprocating bore honing, the two motions produce crossing traces. As a bounded equipment example, Sunnen's **SV-35** product description uses coordinated spindle and stroker control to maintain a selected crosshatch angle along a bore. Its rough/finish cycles are distinct controls. This is a capability of that documented machine, not an operating recipe for another platform. [Sunnen SV-35 crosshatch controls](https://www.sunnen.com/products/sv35-vertical-honing-machine)

**Original ideal-kinematics example:** unwrap the bore wall into a plane. Let circumferential surface speed be `vt` and constant axial speed magnitude be `va`, equal on the up/down passes. Each trace is inclined by `atan(va/vt)` to the circumferential direction. For the example where this inclination is below 45°, the acute included angle between the two ideal trace directions is:

`included angle = 2 × atan(va/vt)`.

Assume **D = 50 mm**, **N = 120 rpm** and **va = 0.100 m/s**. Then:

`vt = π × 0.050 × 120 / 60 = 0.31416 m/s`

`included angle = 2 × atan(0.100 / 0.31416) ≈ 35.31°`.

The model excludes acceleration, reversal, dwell, tool deformation and contact changes. Keep the angle to the bore axis distinct from the acute included angle.

## Original stock-removal check

Assume a perfectly cylindrical bore must increase from **24.980 to 25.000 mm** diameter. Diametral stock removal is **0.020 mm**, while radial removal per surface is half that: **0.010 mm**. Confusing the two doubles or halves a planning allowance.

This arithmetic supplies no material-removal rate, cycle time or correction capability. Real incoming taper, lobing and damage can require different local removal. Verify that sufficient allowance remains to meet the final geometry and texture together, without exceeding the upper size limit.

## Inspection and production handoff

Measure enough axial stations and angular directions to reveal the expected form errors. Where cylindricity or another complete geometric requirement applies, use a suitable evaluation rather than reporting only a two-point diameter. Keep the datum/reference construction and feature extent where required by the drawing.

Assess texture using the specified parameters and method, and inspect after the agreed cleaning stage. Retained abrasive, swarf or fluid can affect downstream assembly or service; define cleaning and residue acceptance for the actual component instead of assuming a visually bright bore is ready for use.

Preserve the part/revision, material state, incoming bore data, stock allowance, tool/abrasive/fluid identifiers, qualified machine and motion window, support condition, tool-wear controls, cleaning route and separate size/form/texture results. Recheck changes that affect the qualified outcome. These are proposed handoff fields rather than a normative process plan.

## Source scope

The cited Sunnen guides print **DF-103 9/09 - POD** and **DF-104 9/09 - POD**, both with ©2009 on their final pages. These printed identifiers, rather than filenames or hosting timestamps, establish the cited document versions. The Sunnen and Gehring live pages have no verified technical revision date here. Named machine and development examples do not establish universal capability. The motion and stock-removal calculations are original bounded illustrations.

[Surface-finishing processes](index.md)