# Fillet Chamfer Last Atomic Skill

## When to use

- A machined part needs edge breaks, deburring chamfers, assembly lead-ins, stress-relief fillets, or small finishing rounds.
- The edge treatment is secondary to the main body, holes, pockets, slots, and bores.

## Do not use when

- The rounded or chamfered profile is the primary defining shape, such as an O-ring groove, cam surface, ergonomic shell, or turbine blade.
- A sharp edge is explicitly required for sealing, locating, scraping, or mating.
- The chamfer/fillet would remove critical wall thickness around a hole, shoulder, or thin rib.

## Recognition features

- SolidWorks feature evidence such as Chamfer, Fillet, radius values, or angle-distance chamfers.
- STEP evidence with conical or toroidal surfaces near final edges.
- Descriptions mentioning chamfered edges, rounded corners, smooth transitions, edge relief, assembly ease, or stress reduction.

## Core invariants

- Apply edge treatments after primary solids, holes, bores, pockets, slots, and patterns are stable.
- Keep edge treatment small relative to nearby feature size and wall thickness.
- Use chamfer for lead-in/deburring and fillet for stress relief or smooth load transition.
- Select specific edges; do not blindly fillet or chamfer every edge.
- Preserve functional shoulders, datum faces, seal lands, and fastener seats.

## Parameter roles

- `chamfer_distance` defines bevel size.
- `chamfer_angle` defines bevel angle, often 45 degrees when not otherwise specified.
- `fillet_radius` defines round size.
- `edge_set` defines which edges receive treatment.
- `minimum_wall_after_edge_treatment` protects small holes, ribs, and pockets.

## Construction sequence

1. Complete the main body and all functional cuts.
2. Identify functional edges that need lead-in, deburring, stress relief, or handling safety.
3. Apply chamfers to hole entrances, exposed outer edges, or insertion edges.
4. Apply fillets to internal corners, web transitions, and load-bearing transitions.
5. Verify that holes, slots, shoulders, and bearing seats remain intact.

## Common failures

- Adding large fillets early and causing later cuts or patterns to fail.
- Chamfering a bearing shoulder, seal land, or datum face that should remain crisp.
- Using one global fillet radius across tiny holes and large outer edges.
- Treating decorative edge rounding as more important than functional geometry.

## Evidence summary

- Current library evidence: 58 reviewed SCAD58 machined parts with final chamfer/fillet operations.
- Latest run evidence: high-frequency accepted insights for `chamfer_edges`, `chamfer_edges_for_safety`, `apply_chamfer_to_edges`, `apply_fillet_to_edges`, and stress-relief fillets.
- Frequent operations in the latest run: Chamfer and Fillet after Extrusion, Cut, HoleWzd, Pattern, and Revolution.
- Source: CAD-SkillX offline review of SCAD58 descriptions, STEP summaries, and SolidWorks feature evidence.

## Retrieval metadata

Triggers:
- `fillet chamfer last`
- `edge treatment`
- `chamfered edges`
- `filleted edges`

Secondary triggers:
- `deburr`
- `assembly lead in`
- `stress relief`
- `smooth transition`
- `edge break`

Operation triggers:
- `chamfer`
- `fillet`
- `apply edge treatment after cuts`

Exclusions:
- `primary rounded profile`
- `sharp datum edge`
- `seal land`
- `cam surface`