cadSet/text-to-cad/skills/cad/references/cad-skillx/atomic/coaxial-bore-rule.atomic.md

Coaxial Bore Atomic Skill

When to use

• A model contains nested cylindrical features that must share one axis: bore, pocket, hub, sleeve, shaft clearance, bearing seat, pilot diameter, or counterbore.
• The request mentions concentric, coaxial, central bore, shaft hole, bearing pocket, or flanged cylindrical geometry.

Do not use when

• Circular holes are independent mounting holes on a plate face.
• The circular features intentionally use different centers.
• The shape is decorative and has no functional axis.

Recognition features

• Central bore or shaft clearance through a rotational or support body.
• Concentric circles in sketch evidence.
• Cylindrical faces nested around one axis.
• Bearing seat, flange hub, sleeve, bushing, washer, spacer, or shaft-like part.

Core invariants

• Use one explicit construction axis or shared sketch origin for all central cylindrical features.
• Distinguish each diameter by role: clearance, seat, counterbore, outer diameter, pilot, groove.
• Cut through holes through all relevant material; cut seats and counterbores only to their functional depth.
• Do not create separate sketches whose centers can drift.

Parameter roles

• axis is the shared centerline.
• bore_diameter controls the through opening.
• seat_diameter controls bearing/pilot/counterbore fit.
• outer_diameter controls surrounding material.
• depth controls blind pocket, counterbore, or groove depth.
• lead_in_chamfer controls assembly entry.

Construction sequence

1. Define the shared axis using the sketch origin, construction line, or selected cylindrical face.
2. Sketch concentric circles or a revolved profile from that axis.
3. Cut the smallest through bore first when it establishes shaft clearance.
4. Cut larger seats, pockets, or counterbores to controlled depth.
5. Add grooves, chamfers, and fillets after the primary coaxial cuts are stable.

Common failures

• Off-axis bore because each circle was sketched from a different center.
• Confusing through bore diameter with bearing seat diameter.
• Cutting the bearing pocket through all and deleting the shoulder.
• Treating unrelated bolt holes as coaxial features.

Evidence summary

• Current library evidence: 50 reviewed SCAD58 flange and bearing-seat models.
• Latest run evidence: accepted insights for central bore alignment, concentric circles, bearing seats, flanges, washers, bushings, and axisymmetric bodies.
• Frequent operations in the latest run: Cut, RevCut, Revolution, Extrusion of concentric circles, Chamfer.
• Source: CAD-SkillX offline review of SCAD58 descriptions, STEP summaries, and SolidWorks feature evidence.

Retrieval metadata

Triggers:

• coaxial bore
• central bore
• concentric
• shaft clearance

Secondary triggers:

• bearing seat
• pilot bore
• counterbore
• hub
• sleeve

Operation triggers:

• concentric sketch
• cut through bore
• counterbore to depth
• revolved cut

Exclusions:

• random face holes
• rectangular hole grid
• offset holes