# Grooving & Parting Tool Width Selection Chart

> Parting and grooving insert widths by diameter per Sandvik, overhang rigidity rules, and standard groove widths for O-rings, retaining rings and thread reliefs.

https://www.sinbo-machining.com/wiki/reference/grooving-parting-widths/

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## On This Page

- Parting / cut-off insert width by part diameter
- External, Face and Internal Grooving
- Standard Groove Widths by Function
- Overhang, Clamping and Cutting Force
- How to Use These Numbers
- Frequently Asked Questions
- Standards & Sources
- Related Pages
- Download This Table

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# Grooving & Parting Tool Width Selection

Parting and grooving insert widths by diameter per Sandvik, overhang rigidity rules, and standard groove widths for O-rings, retaining rings and thread reliefs.

## Parting / cut-off insert width by part diameter

| Part diameter D (mm) | Insert width CW (mm) | Min. practical width (mm) | Setup note |
| --- | --- | --- | --- |
| D ≤ 10 | 1.0 | 1.0 | Slender rods and tubes: the smallest width with the sharpest edge, to minimise cutting force and vibration. |
| 10 < D ≤ 25 | 1.5 | 1.5 | Medium parting; keep the overhang as short as possible. |
| 25 < D ≤ 40 | 2.0 | 2.0 | Rigid set-up; a 2-edge insert is fine. |
| 40 < D ≤ 50 | 2.5 | 2.5 | — |
| 50 < D ≤ 65 | 3.0 | 3.0 | Deep parting: single-edge insert with a stable spring clamp — insert stability is critical at these forces. |
| 65 < D ≤ 100 | — | — | No verified vendor table value; large diameters need a taller blade and stable clamping. Size from the manufacturer catalogue — do not extrapolate. |
| D > 100 | — | — | Sandvik parts diameters up to ≈180 mm with Y-axis CoroCut QD — that is a set-up capability, not a width value. |

> **How to read this table.** Widths are the published Sandvik Coromant table, which ends at Ø65 mm. No vendor width table in our sources covers 65–100 mm or above 100 mm — size those from the tool maker's catalogue; do not extrapolate the ladder.

## External, Face and Internal Grooving

Only external grooving has a published width table — the same ladder as parting. Face and internal grooving are set by chip evacuation, groove curvature and overhang, so they are designed per part rather than read off a chart.

| Grooving type | Width guidance | Main difficulty |
| --- | --- | --- |
| External grooving / parting | Standard insert widths 1.0 / 1.5 / 2.0 / 2.5 / 3.0 mm — take the narrowest that carries the groove | Narrower blades cut with less force and waste less material, but they need stable clamping and a short overhang. |
| Face grooving | No universal width table — the tool path follows the groove curvature | Chip evacuation and the groove bending radius decide the tool path; overhang and vibration are the main difficulties. |
| Internal grooving | No published diameter-to-width table | Long overhang, chip evacuation, vibration and tool stability; use solid or damped bars with through coolant. |

## Standard Groove Widths by Function

Functional grooves take their width from the mating standard, not from preference: retaining-ring grooves equal the ring thickness, O-ring grooves follow the seal design rules, thread reliefs follow the thread standard. Non-functional grooves should drop onto a standard insert width so no custom tooling is needed. Depth proportions for O-ring grooves are not listed here — read them from the standard (ISO 3601-2 / GB/T 3452.3) for the exact cross-section.

| Groove function | Common groove width | Tolerance & related dimensions | Standard |
| --- | --- | --- | --- |
| O-ring seal groove, static | ≈ 1.3–1.9 × cross-section (CS) — CS 1.8 → ≈ 2.3–3.4; CS 2.62 → ≈ 3.4–5.0; CS 3.53 → ≈ 4.6–6.7; CS 5.33 → ≈ 6.9–10.1 (mm) | Static squeeze 15–30%; groove-bottom radius R0.1–0.3 | ISO 3601-2 / GB/T 3452.3 |
| Retaining-ring groove, shaft (DIN 471 type) | Groove width = ring thickness s — shaft Ø30 → s ≈ 1.5; Ø50 → s ≈ 2.0; Ø100 → s ≈ 3.0 (mm) | Shaft Ø30: groove-bottom diameter d3 ≈ 27.5–28.1 mm; width toleranced per the standard table | DIN 471 / GB/T 894.1 |
| Thread-relief / undercut groove | At least the tool cutting width, plus a 0.5–1 mm margin | Free tolerance; dimensioned as width × depth or width × diameter | GB/T 3-1997 |
| Functional / non-standard groove | 2 / 2.5 / 3 / 4 mm — standard insert widths cut it without custom tooling | Designer-defined; check the mating standard if a ring or seal seats in it | Standard insert width ladder (1 / 1.5 / 2 / 2.5 / 3) |

## Overhang, Clamping and Cutting Force

The width choice only pays off if the set-up is stiff. These relations come from Sandvik's parting and grooving knowledge base.

| Rule | Numbers | Practical effect |
| --- | --- | --- |
| Shorten the overhang before upgrading anything else | Deflection grows with the cube of overhang: 100 → 80 mm overhang ≈ 0.51× the deflection | A shorter overhang beats any insert upgrade at the same width. |
| Y-axis parting raises stiffness | Y-axis parting: more than 6× the bending stiffness at a 60 mm blade overhang | Less vibration and a higher allowable feed. |
| Feed threshold on overhang | Overhang under 1.5 × blade height (H): recommended feed; beyond it, drop to the low end of the feed band | Measure the real overhang before choosing the feed. |
| Clamp the bar long enough | Bar clamping length ≥ 4 × bar diameter D | Shorter clamping lets slender bars whip and pinch the blade. |
| Narrow blade, lower force | Narrower insert: lower cutting force, less swarf; small widths lower radial force on fragile parts | The trade is setup sensitivity — clamp close and keep the overhang short. |

## How to Use These Numbers

- Non-functional groove widths should land on 2 / 2.5 / 3 / 4 mm so a standard insert cuts them in one pass — no custom tooling, no second operation. Functional grooves (seals, retaining rings) take the standard's width instead of an invented value.
- Up to Ø10 mm part with a 1.0 mm blade; 10–25 mm with 1.5 mm. Narrower blades mean less cutting force and less material scrapped, but they punish a loose setup: clamp the bar at ≥ 4 × D and work close to the chuck.
- Keep the blade overhang under 1.5 × blade height. Beyond that, drop the feed to the low end of the recommendation — deflection grows with the cube of overhang, and Y-axis parting buys back more than 6× stiffness at 60 mm overhang.
- Set the blade on centre within ±0.1 mm, especially when cutting through to the axis. Off-centre parting raises burrs and flanges and chips corners.
- Never tweak a retaining-ring groove: for a Ø30 shaft, DIN 471 wants width = ring thickness s ≈ 1.5 mm and groove-bottom diameter d3 ≈ 27.5–28.1 mm. A wider or deeper groove stops the ring from doing its job.

## Frequently Asked Questions

### What grooving insert width should I use to cut off a Ø25 mm bar?

1.5 mm — Ø25 sits in the 10–25 mm band. The next band up (25–40 mm) takes 2.0 mm.

### What groove width for a retaining ring on a Ø30 mm shaft (DIN 471)?

The ring thickness: s ≈ 1.5 mm, with groove-bottom diameter d3 ≈ 27.5–28.1 mm per DIN 471 — not 2.5–3 mm.

### How wide should an O-ring groove be for a 3.5 mm cross-section O-ring?

Static groove width ≈ 1.3–1.9 × CS, so 4.6–6.7 mm for a 3.5 mm cross-section, per the ISO 3601-2 / GB/T 3452.3 design rules. Take the depth proportions from the standard for the exact cross-section.

### Can I cut a Ø40 mm part with a 3 mm grooving insert?

40–50 mm calls for 2.5 mm; 3.0 mm is the 50–65 mm band. It works, but the over-width blade adds cutting force and wastes material on a Ø40 part.

### What is the smallest parting width for a thin Ø8 mm rod?

1.0 mm (the ≤10 mm band). On fragile, slender parts use the smallest width with the sharpest edge.

### Does a narrower insert reduce cutting force?

Yes — a narrower insert cuts with less force and wastes less material, and small widths also lower radial force on fragile parts. The price is a stiffer, closer setup.

### What is a safe overhang for a parting blade?

Under 1.5 × blade height; beyond that, drop the feed to the low end. Deflection grows with the cube of overhang — at 60 mm overhang, Y-axis parting is more than 6× stiffer.

## Standards & Sources

- Sandvik Coromant knowledge base — Parting off (insert width by diameter; overhang, clamping and Y-axis stiffness relations)
- Sandvik Coromant knowledge base — Tool set-up, Face grooving and Internal grooving pages
- ISCAR Swiss-Cut / ISO turning selection principles — small widths for small or fragile diameters
- DIN 471 retaining-ring dimension table (secondary database source; confirm against the standard text; Chinese equivalent GB/T 894.1)
- O-ring groove width proportions per ISO 3601-2 / GB/T 3452.3 design rules — example tiers calculated from the ratio, not read from the standard tables
- Thread-relief dimensioning per GB/T 3-1997 (free tolerance; width × depth or width × diameter callout)

## Related Pages

- [/wiki/reference/relief-undercut-chamfer/](/wiki/reference/relief-undercut-chamfer/) — Sibling quick table: thread undercuts (GB/T 3, DIN 76) and chamfer standards
- [/wiki/reference/cutting-parameters/](/wiki/reference/cutting-parameters/) — Sibling quick table: cutting speeds and feeds for turning and milling
- [/wiki/dfm/tolerance-design/](/wiki/dfm/tolerance-design/) — How to tolerance grooves and fits on the drawing
- [/wiki/tolerances/fit-types/](/wiki/tolerances/fit-types/) — When a groove needs an individual tolerance instead of a general one

## Download This Table

- CSV — /wiki/reference/download?slug=grooving-parting-widths&format=csv&lang=en
- JSON — /wiki/reference/download?slug=grooving-parting-widths&format=json&lang=en
- Markdown — /wiki/reference/grooving-parting-widths/index.md