# K03 rear-access cover — matched final interface

The adapter cover is revised to accept two rear-access M2 × 6 pan screws. Its electronics, carrier outline, connector pose and split grommet remain fixed. The former horizontal screws overlapped the added cable-support webs; the final design retains broad webs and uses separate, hard-seated ears. Use this cover only with the final adapter base and hardware manifest.

## Geometry and hardware

| Feature | Final value |
|---|---|
| Cover | `cad/controls/K03_R36_TERMINATION_CLEARANCE_FINAL.step` |
| Cover SHA256 | `580eec6470b4cfe0304f8378489ee699dc3c6570e690a23949fec2dae7483077` |
| Shape | Valid, one solid; 403.177425 mm³ |
| Screw axes | Left X = 15.6, right X = 28.1; both Y = −6.05 mm, parallel to Z |
| Screws | M2 × 6, maximum modeled pan head Ø4 × 1.6 mm |
| Head extent / bearing seat | Z = −10.1…−8.5 mm / Z = −8.5 mm |
| Ear thickness / post hard seat | 2.0 mm / Z = −6.5 mm |
| Clearance / pilot | Ø2.2 / Ø1.7 mm |
| Potential engagement / tip margin | 4.0 / 0.6 mm; tip at −2.5, pilot floor at −1.9 mm |
| Post clearance | 0.30 mm nominal radial clearance above the hard seat |
| Local front crescent | Ear trimmed to Y = −3.95; 0.20 mm nominal clearance to the carrier backer |
| Actual head-bearing area | Left 8.765044; right 8.763837 mm² |

An ideal Ø4 head around a Ø2.2 bore has 8.765044 mm² of bearing area. The bounded carrier clearance removes 0.001206 mm² from the right seat, about 0.014%; the rest remains supported. The front ear trim stays 2.10 mm from the screw axis, outside the Ø4 head. It does not remove the bearing face.

The fixture agent's final post audit reports 1.20548 mm from the left pilot to its wire channel and 0.96161 mm on the right. The right carrier-side pilot ligament is 0.95 mm. These are short, supported receiver regions, not a general recommendation for free-standing walls. Do not assume a printed Ø1.7 pilot will accept an M2 screw safely: qualify the actual pilot/tapped-thread method on the matched QF01B coupon. The original curved front skin remains approximately 1.8999 mm beyond the blind pilot floor.

## Checks and their scope

- [Paired fit and access](K03_pair_and_access.json): the final cover has zero solid overlap with the complete `P01_ADAPTER_FINAL_REPLAY_REVIEW.step` host. Carrier, all four edge pads, header, solder insulation and factory-connector reference also clear. Rear pads and grommet have intended zero-gap surface contact. Cover-to-carrier gap is 0.25 mm; corrected solder-insulation gap is 0.36 mm, bare-conductor gap 1.02 mm, and header gap 0.96 mm. The front opening is a rounded rectangle around the actual corrected insulation bounds with a 0.36 mm X/Z margin and R0.20 corners. The grommet pocket and pose remain unchanged.
- [Preassembled rear insertion](K03_preassembled_insertion.json) checks the complete soldered carrier/header/insulation/cover/pad module at nine positions over 12 mm of rear-Z insertion against the full host. All nine clear. The manufactured flexible pigtail is undressed and the factory battery plug is disconnected. These are sampled paths, not a certification of every possible handling trajectory.
- The expanded rails make a cover-only rear insertion past already fixed solder joints unsuitable; the diagnostic path report records those collisions. Installing the complete module avoids that crossing. A straight cable-side insertion of the complete module also meets a host feature and is not the selected sequence.
- Straight Ø3 mm, 30 mm-long driver shafts clear the cover, full front host and all retained reference geometry when the rear shell and main PCB/module are absent. The board obstructs both tools when installed. This is an assembly-order requirement, not an instruction to force or angle a driver through the PCB.
- The exact analytic full screw/post envelopes clear the persisted cover. The fixture agent independently checks the actual final screw-reference files and neighboring wires/electronics. Final integrated hardware checks remain part of the root delivery audit.

## Local load screen

[Actual-section calculations](K03_local_strength.json) use the persisted final STEP. A 10 N total pull at either fixed wire centre produces at most 6.22 N at one longitudinal web; the model rounds this to 6.25 N and uses the full 5.25 mm lever arm to the screw axis. The ear transition is separately screened at 10 N. The minimum sections are integrated from 0.002 mm slices.

The two grommet-slot rails are checked **independently**, without crediting coupled stiffness. Each receives a conservative 10 N midpoint load over a 5.8 mm span. Solid subtraction confirms that the modeled minimum rectangular sections are contained in the actual STEP: depth 6.0 mm, lower height 2.025 mm and upper height 2.14 mm. The rear upper portion is taller; 2.14 mm is the conservative minimum after positive termination clearance.

All calculations use hypothetical E = 1,000 MPa and an 8 MPa screening limit, with a factor of two on nominal bending stress. The lower rail screens at **7.07 MPa**, the upper at **6.33 MPa**, and the highest longitudinal-web result is **7.28 MPa**. Estimated elastic deflection stays below **0.010 mm**. The ear transitions screen below 0.94 MPa. A direct 10 N force over one head-bearing annulus averages approximately 1.14 MPa.

These are comparison calculations, not printed material, thread, fatigue, creep or connector retention qualifications. The earlier 6.94 MPa web-only result is superseded. [The final delta proof](K03_final_removal_delta.json) confirms this version only removes 21.920157 mm³ from the preceding 04c4 cover, with a valid empty added-material difference; its positive-clearance opening leaves the strengthened rails intact.

## Assembly and physical gates

1. Thread the two manufactured adapter-pigtail conductors through the loose cover opening before soldering them to the carrier. Install the split silicone grommet without cutting or splicing the factory battery cable.
2. Preassemble the soldered carrier, header, insulation, pads and cover outside the shell, then insert the module from the open rear before the main PCB and before final dressing of the nearby harness. Keep the carrier on its padded locating faces, and hold the cover at its Y = −5.25 datum while seating the two rear screws on their hard posts.
3. Use the measured head envelope and a suitable straight driver no larger than the tested Ø3 mm shaft. For service, remove the main PCB before accessing these screws.
4. Qualify the matched receiver/cover coupon, pilot preparation, repeated servicing and grommet grip with the actual process and stock. Verify that cable pull goes into the grommet/cover/posts, not the soldered pins or FR4 carrier. Reject splitting, stripping, bottoming, loose carrier capture or insulation damage.

Final native export and complete assembly checks are separate evidence. Physical printing, thread formation and cable-pull tests have not been performed by this CAD audit.