cdsl-cad/backend/agent/skills/cad-engine/references/part-skills/source/planning/hexagonal-nut.planning.md

Hexagonal Nut Planning Skill

When to use

• The request describes a hex nut, hexagonal nut, machined nut, nut-like fastener, or hexagonal threaded insert.
• The key features are wrench flats, a central threaded bore, and chamfered faces/edges.

Do not use when

• The part is a bolt, screw, socket head cap screw, threaded rod, wing nut, cap nut, or flange nut unless the prompt explicitly asks for that variant.
• The hexagon is only a decorative grip on another part.
• The threaded feature is external rather than an internal bore.

Recognition features

• Six flat wrench faces or hexagonal prism envelope.
• Central internal threaded hole coaxial with the nut thickness.
• Chamfers on top and bottom openings and on hex edges.
• Optional counterbore, lead-in chamfer, or relieved thread entry.

Core invariants

• Keep the threaded bore centered through the hex body.
• Preserve the hex across-flats size separately from thread size and thickness.
• Model chamfers as functional lead-ins and edge breaks, not as random bevels.
• Represent internal thread intent using a threaded hole, thread callout, or helical/revolved cut only when required by output format.
• Do not generate the mating bolt unless requested.

Parameter roles

• across_flats defines wrench size.
• thickness defines nut height.
• thread_size, thread_diameter, and thread_depth define the central bore.
• bore_diameter defines the pre-thread or clearance hole if thread geometry is abstracted.
• face_chamfer and edge_chamfer define lead-in and deburring.

Construction sequence

1. Create the hexagonal body as a hex extrusion or by cutting flats from a revolved/chamfered blank.
2. Define the central axis through the nut.
3. Create the central bore or threaded hole through the body.
4. Add thread representation or thread callout if the CAD output supports it.
5. Add top/bottom lead-in chamfers and small edge chamfers.
6. Verify the hex flats remain planar and the bore remains coaxial.

Common failures

• Producing a bolt or screw instead of a nut.
• Forgetting the central threaded bore.
• Placing the bore off-center relative to the hex body.
• Making the chamfers so large that wrench flats disappear.
• Treating a flange nut, cap nut, or wing nut as a plain hex nut.

Evidence summary

• Latest run evidence: 25 accepted planning insights matched hex nut or nut-like threaded fastener descriptions.
• Strong repeated names include plan_hex_nut, revolved_hex_nut_with_internal_thread, hex_nut_construction, and plan_hexagonal_nut_with_threaded_bore.
• Frequent operations in the latest run: Revolution, Extrusion, Cut, RevCut, HoleWzd, Chamfer.
• Source model examples: 009934, 010137, 052867, 066148, 067249, 135604, 138372, 150622, 200147, 204805, 222550, 225767, 231397, 238840.
• Source: CAD-SkillX offline review of SCAD58 descriptions, STEP summaries, and SolidWorks feature evidence.

Retrieval metadata

Triggers:

• hex nut
• hexagonal nut
• nut
• threaded nut
• hexagonal threaded insert

Secondary triggers:

• internal thread
• central threaded bore
• wrench flats
• across flats
• chamfered nut

Operation triggers:

• extrude hexagon
• cut central bore
• hole wizard threaded hole
• revolved cut thread
• chamfer faces

Exclusions:

• bolt
• screw
• threaded shaft
• wing nut
• cap nut
• flange nut