The short answer
A **rotary-seal face groove** on a CNC housing is not an [O-ring gland](https://3dwk.com/resources/o-ring-groove-callouts-cnc-housings). It is a rectangular housing seat for a rotary shaft seal—typical **DIN 3760 / ISO 6194** style packaging—where the seal OD sits in a bored land and the lip runs on a shaft diameter. A usable callout names the **housing bore**, the **groove width**, limited corner radii, a lead-in, the location from a face, and the **shaft land** (diameter and roughness) that the lip actually sees. Silence on that pack is what widens many [quote-new.php](https://3dwk.com/quote-new.php) **rates.v1.1** estimate bands—not the extra minutes of a boring pass alone.
This guide is for buyers packaging housings where a lip-seal pocket is modeled as a square groove or labeled only “oil seal.” Illustrations use an **Example part** only—not a customer gearbox. Sibling notes live in [O-ring groove design](https://3dwk.com/resources/o-ring-groove-design-cnc-housings) and [leak-test notes for CNC housings](https://3dwk.com/resources/when-to-specify-leak-test-cnc-housings); here we focus on **rectangular rotary-seal packaging**, not elastomeric O-ring glands.
What a rotary-seal face groove means for quoting
A **rotary-seal housing groove** names a bore for the seal OD, a width slightly larger than the seal case, a max corner radius so the case can sit, and a lead-in at the mouth. The **shaft land** is a separate feature: running diameter, roughness, and a lead-in of its own, with no harmful turning spiral that pumps fluid past the lip. Writing “standard oil-seal groove, seal as needed” is not enough. Process pages for aluminum housings ([CNC 3-axis Al 6061 automation](https://3dwk.com/en/cnc-3axis/al-6061/automation.html), [CNC turning Al 6061 automation](https://3dwk.com/en/cnc-turning/al-6061/automation.html), [CNC 3-axis Al 6061](https://3dwk.com/en/cnc-3axis/al-6061.html)) assume the seal family is visible when lots mix lip-seal bores with [O-ring face glands](https://3dwk.com/resources/o-ring-groove-callouts-cnc-housings) on the same block.
Do not bury “standard seal groove” inside a notes cloud. Put **FACE GROOVE A: HOUSING BORE Ø35 H8, WIDTH 8, CORNER R 0.3 MAX, LEAD-IN 1 × 45°, 4 FROM FACE A; SHAFT LAND Ø20, Ra 0.4, NO HARMFUL LEAD** on the PDF and mirror it in RFQ text. Background: [surface-roughness Ra callouts](https://3dwk.com/resources/surface-roughness-ra-callouts-that-raise-quotes), [what files to send for a CNC quote](https://3dwk.com/resources/what-files-to-send-for-cnc-quote), [housing design tips](https://3dwk.com/resources/five-axis-aluminum-housing-design-tips).
Housing bore versus shaft land
The housing is a rectangular-section seat, not a dash-size O-ring groove and not a dovetail. Typical catalog language follows DIN 3760 / ISO 6194 style packaging; use those families as a named target, but still write the bore, width, and radii you will accept. The shaft land is where the lip runs—[Ra callouts](https://3dwk.com/resources/surface-roughness-ra-for-machined-parts) tighter than the rest of the turning should be limited to that diameter, not the whole shaft.
A lead-in chamfer at the housing mouth and on the shaft should not eat the land width. [Retaining-ring grooves](https://3dwk.com/resources/internal-retaining-ring-groove-notes-cnc-bores) next to a seal bore should stay clear of the rectangular seat.
Aluminum 6061 plate and billet $/kg planning bands sit in the common CNC aluminum range under **rates.v1.1** material tables; material cost is rarely the groove-family story—bore class, width, and shaft-land finish are.
Width, corners, and location
Name the groove width, remaining wall, and location from a face or shoulder. Tight corners copied from an O-ring gland, or a width taken from a seal catalog without a housing allowance, both create a case that will not seat. If the groove is open to a face, say whether a pressed-in seal is installed from that face and whether a later [leak test](https://3dwk.com/resources/when-to-specify-leak-test-cnc-housings) needs a plug method.
Tolerance and inspection traps
Calling “oil seal groove for Ø20” with no housing bore or width, copying an [O-ring gland](https://3dwk.com/resources/o-ring-groove-design-cnc-housings) onto a lip-seal note, or putting a fine Ra on the entire housing, all force **needs_manual**. Default the rectangular seat to a named bore, width, and corner, and limit fine finish to the shaft land. Related: [ISO 2768 general tolerances on CNC RFQs](https://3dwk.com/resources/iso-2768-general-tolerances-cnc-rfq), [what needs_manual means](https://3dwk.com/resources/what-needs-manual-means-preliminary-quote).
Illustration 1 shows an **Example part** housing with a labeled rectangular rotary-seal seat (Ø35 H8 × width 8) versus an O-ring face gland that must not be used as a stand-in.
Example part walkthrough
**Example part:** Aluminum 6061-T6 housing ~80 × 50 × 30 mm, rectangular rotary-seal groove consistent with a 20 × 35 × 7 class package (DIN 3760 / ISO 6194 style—typical values, not a catalog certificate): housing bore Ø35 H8, width 8, corner R 0.3 max, 1 × 45° lead-in, 4 mm from face A, shaft land Ø20 with Ra 0.4 and no harmful turning lead, ISO 2768-m general elsewhere. With STEP + **HOUSING Ø35 H8 × W8 R0.3 MAX, 4 FROM A; SHAFT Ø20 Ra 0.4**, expect a usable automatic planning band on [quote-new.php](https://3dwk.com/quote-new.php). Same geometry with silent “standard oil-seal groove” often lands DFM notes or **needs_manual**—without inventing any customer PO.
Illustration 2 contrasts a vague RFQ (“standard oil seal”) versus a labeled housing-and-shaft pack and the clearer estimate path.
What widens bands fastest
Unlabeled mix of O-ring glands and lip-seal seats, missing housing bore or width, sharp corners, and a fine Ra painted on every turned diameter. Quantity breaks help unit minutes but do not erase seal-family ambiguity—see [how quantity breaks change CNC unit cost](https://3dwk.com/resources/how-quantity-breaks-change-cnc-unit-cost) and [DFM checklist](https://3dwk.com/resources/dfm-checklist-before-online-cnc-quote).
What to do next
Mark each rotary-seal seat with a **housing bore, width, corner, lead-in, location, and shaft-land finish**, then upload on [quote-new.php](https://3dwk.com/quote-new.php). Packaging checklist: rectangular lip-seal seat versus O-ring gland, and a shaft land that is not the housing bore. Service pages: [CNC machining](https://3dwk.com/cnc-machining-service.php), [materials](https://3dwk.com/materials.php). Treat **rates.v1.1** min/mid/max as estimates, not invoices. If the UI shows **needs_manual**, answer the seal-family questions rather than forcing a fake price.
Common questions
Can I reuse an O-ring groove for a rotary shaft seal?
No, not as a silent stand-in. An O-ring gland is sized for an elastomeric torus; a rotary shaft seal needs a rectangular housing seat and a separate shaft land. If both exist on one housing, draw them as two features.
Do I have to quote a DIN 3760 or ISO 6194 number?
Name the family if that is the package you want, but still write the housing bore, width, and radii you will inspect. A catalog number alone, with no housing dimensions, is not a complete RFQ.
How fine should the shaft land be?
Only as fine as the lip requires, and only on that diameter. A whole-shaft Ra copied from a seal catalog will widen the band. Say “no harmful turning lead” when spiral feed marks would pump fluid past the lip.
Where should the lead-in go?
On the housing mouth and on the shaft entry, sized so they do not eat the seat width or the running land. Write the chamfer and the remaining width.