O-ring nut in Fusion in 30 seconds: the O-ring nut generator

One edge is enough

The workflow follows design practice: You have a shaft or a bore and look for the matching ring—not the other way around. So, in the dialog box, you simply select a circular edge on the shaft shoulder or bore. The add-in measures the diameter, automatically detects whether it's a piston or rod seal, and suggests the appropriate standard O-rings—best fit first.

Important and technically correct: Matching is done at the seat, not at the piston diameter. For piston grooves, the ring sits in the groove base (target approx. 2% elongation), for rod grooves, it sits on the rod (approx. 1%). The seat diameter is specified in each proposal, e.g., "15 × 3 mm — sits on groove base Ø 15.30 (+2.0%)".

Chamfered or rounded edges also work: The chamfer is skipped, and the cylinder behind it becomes the groove carrier. The offset from the edge to the start of the groove has a draggable arrow in the model—similar to extrusion; "Reverse direction" places the groove on the opposite side.

Design according to ISO 3601 guidelines

Groove depth, groove width, groove base and edge radii, compression, sealing gap, and fill level are calculated live and displayed in the results field—including warnings if something is amiss: fill level too high, groove too close to the edge, remaining web too small. Manufacturing instructions with tolerance recommendations (groove base h11, bore H8) and Ra values for the groove and sealing surface are also provided. Users with their own factory standards can manually override each value under "Design (Guideline Values)."

Four sealing types are covered: piston groove (radial), rod groove (radial), axial groove for internal pressure and axial groove for external pressure/vacuum.

An element in the timeline

The groove is stored as a single, named element in the timeline—no feature clutter of sketches, layers, and sections; the design history remains readable. If the groove needs to be changed: delete the element, restart the command—thanks to the O-ring finder and live preview, this takes seconds.

Optionally, the add-in also generates the O-ring: nominally as a torus or built-in and deformed with a volume-preserving profile and rubber material — for correct representation, sectional views and mass properties.

Price and availability

The O-ring nut generator is available in the Autodesk App Store for Windows and macOS, with German and English interfaces (automatically following the Fusion language). Price: $29 (one-time fee, no subscription costs).

[LINK: Autodesk App Store product page — register after activation] [VIDEO: 60–90 second screencast of the workflow]

The catalog includes over 800 metric bearing sizes (cord diameters 1.0–6.0 mm); special sizes and inch/AS568 rings can be entered manually. All values are guidelines for standard applications according to ISO 3601 logic and manufacturer practice—for high pressure, temperature extremes, or safety components, as always: check the manufacturer's catalog and ISO 3601-2.

Support and feedback

Questions, requests, special cases? We usually respond within 24–48 hours on weekdays: support@sterndidactic.com . The O-ring groove generator is the first in a whole family of standard elements for Fusion — undercut, center hole, locking groove and keyway generators will follow shortly.