base updates

README.md

@@ -30,7 +30,7 @@ inlays printed against a textured build plate.
 
 | Qty | Item | Relevant dimensions |
 | ---: | --- | --- |
-| 70 | [McMaster 97171A240 brass 1/4-20 heat-set insert](https://www.mcmaster.com/97171A240/) | 9.525 mm body, 12.7 mm flange, 1.27 mm flange thickness, 8.026 mm maximum hole |
+| 70 | [McMaster 97171A240 brass 1/4-20 heat-set insert](https://www.mcmaster.com/97171A240/) | 12.7 mm long, 9.525 mm flange/body envelope, 1.27 mm flange thickness, 8.026 mm maximum hole |
 | 4 | [1/4-20 adjustable foot](https://www.amazon.com/dp/B095PDSNPM) | 19 mm pad diameter, 8.5 mm pad height, 17.8 mm stud |
 | 4 | [Knurled 1/4-20 locking nut](https://www.amazon.com/dp/B0GQSX98V4) | 24.4 mm OD, 6 mm thick |
 | 1 | [European-style 2020 T-slot extrusion](https://www.amazon.com/dp/B08Y8N7FD1) | 20 x 20 x 400 mm, 6 mm slots |
@@ -39,16 +39,19 @@ inlays printed against a textured build plate.
 | 4 | M5 x 10 mm socket-head screws and European 2020 T-nuts | Extrusion clamp; verify screw length against the selected T-nut |
 
 The four feet use four of the listed inserts: two dedicated rear inserts and
-the two shared front grid inserts. Four more dedicated inserts secure the
-socket. The remaining 64 inserts make up the complete grid.
+the two shared outer inserts in the front grid row. Four more dedicated inserts
+secure the socket. Those eight inserts install from the underside. The other
+62 grid inserts install from the working surface.
 
 The McMaster drawing requires at least 0.530 inch (13.46 mm) of material. Every
 insert boss in this design is 15 mm tall, including all four socket-mounting
 bosses. The 52.5 x 22.5 mm locating slot passes through the base between those
-bosses, so it does not reduce their thickness. Inserts install from the open
-underside with their flange flush against the boss. The 1.35 mm flange seat and
-9.525 mm body leave a 4.125 mm screw-clearance tunnel below the clean 6.8 mm
-opening in the working surface.
+bosses, so it does not reduce their thickness. Every insert location uses an
+8.10 mm pilot through the full remaining thickness and a 10.5 mm diameter,
+1.35 mm deep flange relief on its installation face. The 62 accessory-grid
+reliefs face upward; the four corner and four socket-mounting reliefs face the
+open underside. This lets displaced plastic exit from the far end of the pilot
+instead of collecting at a smaller clearance tunnel.
 
 ## Build
 
@@ -80,8 +83,9 @@ alongside them.
 
 Print `coupon_multicolor.3mf` in the intended ASA, face down on the intended
 textured plate. It produces a main coupon and a separate full-size tongue
-gauge. From left to right, the insert pilots are 7.70, 7.85, 8.00, 8.15, and
-8.30 mm. The four rail gauges are 20.0, 20.1, 20.2, and 20.3 mm. Each is a
+gauge. From left to right, the full-depth insert pilots are 7.70, 7.85, 8.00,
+8.15, and 8.30 mm beneath production-size 10.5 mm flange reliefs. The four rail
+gauges are 20.0, 20.1, 20.2, and 20.3 mm. Each is a
 four-wall collar with the production 6 mm side walls, 2.7 mm end walls, and
 full 50 mm engagement depth. External gussets and M5 holes are omitted because
 they do not define the rail-fit surfaces. The coupon also
@@ -130,8 +134,11 @@ provide the base structure; sparse slicer infill is not relied on there.
 
 ## Assembly
 
-1. Heat-set the inserts from the underside. Stop when each brass flange is
-   flush with its counterbore; do not pull it toward the textured top surface.
+1. From the working surface, heat-set the 62 accessory-grid inserts into their
+   10.5 mm flange reliefs. Let displaced plastic exit through the open pilot on
+   the underside. Install the four corner and four socket-mounting inserts from
+   the underside in the same way. Stop when each brass flange is flush with its
+   relief.
 2. Thread the leveling feet through their locking nuts and into the two rear
    foot inserts and two outer inserts of the front grid row.
 3. Lower the socket's 52 x 22 x 14.8 mm tongue into the base's through-slot,
@@ -139,7 +146,7 @@ provide the base structure; sparse slicer infill is not relied on there.
    1-inch screws. The screws provide clamping and vertical retention; the
    tongue provides repeatable X/Y location and carries lateral shear. With a
    washer thickness `t` in millimeters, nominal insert engagement is
-   `11.275 - t` mm, limited by the insert's 9.525 mm threaded length.
+   `11.275 - t` mm within the insert's 12.7 mm length.
 4. Preload two T-nuts in each side slot of the extrusion. Lower the extrusion
    to the socket floor and fasten it through the four M5 clamp holes.
 5. Level the base, then tighten each knurled locking nut against its insert
@@ -156,7 +163,9 @@ above those screws, and 14 mm horizontal tunnels provide driver access to the
 M5 rail clamps without sacrificing the collar wall around the T-slot
 extrusion. The 19 mm fore/aft screw-row spacing and broad flange attachment
 improve overturning and torsional resistance compared with the compact first
-revision.
+revision. Beneath the base, a continuous 3.2 mm wall surrounds the rectangular
+locator slot through the full open-cell depth and merges with the intersecting
+grid ribs.
 
 Before mounting a camera, proof-test the assembled stand with a dummy load at
 the maximum working overhang. Under the normal payload, target less than 1 mm