update socket

README.md

@@ -11,17 +11,18 @@ inlays printed against a textured build plate.
 ## Coordinate system and principal dimensions
 
 - Base: 203.2 x 248 x 15 mm, with 12.7 mm corner radii.
-- The grid origin is Y=0 and positive Y runs toward the operator. The socket's
-  straight front reference face is Y=12.7 mm (0.5 inch), halfway between the
-  origin and the first insert row.
+- The grid origin is Y=0 and positive Y runs toward the operator. The socket
+  flange's straight front reference face is Y=12.7 mm (0.5 inch), halfway
+  between the origin and the first insert row. The extrusion's front face is
+  aligned to Y=0, so either reference can be used for direct measurement.
 - The 8 x 8 insert array has 25.4 mm spacing. Its rows are Y=25.4 through
   Y=203.2 mm relative to the socket datum.
 - A blue Y=0 datum line continues beneath the socket, leaving aligned visible
   segments on both sides.
 - The removable socket captures 50 mm of a nominal 20 x 20 mm extrusion.
 - Its 110 x 38.7 x 10 mm flange reaches from the rear plate edge to the
-  half-inch reference face. The column is shifted forward to improve the
-  overturning load path and reduce the camera arm's required overhang.
+  half-inch reference face. The collar is near the flange center, with tapered
+  side gussets that retain the original broad flange footprint.
 - The two outside inserts in the front grid row also mount the front leveling
   feet. They cannot accept top-side accessories while the feet are installed.
 
@@ -84,22 +85,25 @@ gauge. From left to right, the insert pilots are 7.70, 7.85, 8.00, 8.15, and
 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
-contains the production-width blue line and a 6 mm-deep production-size
-52.5 x 22.5 mm through-slot. The separate 52 x 22 x 6 mm tongue prints in the
-same orientation as the socket tongue and has a support-free stop shoulder and
-vertical grip for insertion and removal. Verify that the slot is visibly open,
-with no first-layer membrane, before testing the fit.
+contains the production-width blue line and a 6 mm-deep 52.5 x 22.5 mm
+through-slot. The separate 52 x 22 x 6 mm tongue is an XY fit gauge for the
+production interface; its shorter depth keeps the calibration print compact.
+It has a support-free stop shoulder and vertical grip for insertion and
+removal. Verify that the slot is visibly open, with no first-layer membrane,
+before testing the fit.
 
 The production model defaults to the physically calibrated 8.10 mm insert
 pilot and 20.1 mm rail cavity. These values were selected from an ASA coupon:
 the 20.1 mm collar accepted the fully cooled rail through all 50 mm by hand
 without objectionable play, and the 8.10 mm pilot provided the preferred
 insert fit. The rectangular tongue and through-slot also passed the physical
-fit test, so their dimensions remain unchanged. For another printer, material,
-or process, select the smallest rail gauge that fits without forcing and use
-the insert pilot that gives the required installation grip. Change
-`insert_pilot_diameter` or `rail_clearance` at the top of `copy_stand.scad`,
-then rebuild. The 8.30 mm coupon remains a diagnostic oversize option;
+XY fit test. The production tongue retains those dimensions and extends 14.8
+mm into the 15 mm base, leaving 0.2 mm underside clearance. For another
+printer, material, or process, select the smallest rail gauge that fits without
+forcing and use the insert pilot that gives the required installation grip.
+Change `insert_pilot_diameter` or `rail_clearance` at the top of
+`copy_stand.scad`, then rebuild. The 8.30 mm coupon remains a diagnostic
+oversize option;
 McMaster specifies 8.026 mm as the maximum nominal hole diameter, while this
 design's 8.10 mm production value reflects the tested print process.
 
@@ -130,11 +134,11 @@ provide the base structure; sparse slicer infill is not relied on there.
    flush with its counterbore; do not pull it toward the textured top surface.
 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 6 mm tongue into the base's through-slot, then
-   fasten the flange with four 0.7-inch OD washers and four 1/4-20 x 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
+3. Lower the socket's 52 x 22 x 14.8 mm tongue into the base's through-slot,
+   then fasten the flange with four 0.7-inch OD washers and four 1/4-20 x
+   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.
 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.
@@ -145,12 +149,14 @@ The Lobster/CS-Lite locating fixture, Arca rail, camera carriage, and camera
 alignment accessories are deliberately deferred. They can attach to the grid
 without changing this base.
 
-The socket's broad side buttresses stop before the four base screws. Vertical
-19 mm washer and tool envelopes preserve access 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 shallower side buttresses improve overturning and
-torsional resistance compared with the compact first revision.
+The socket's tapered side buttresses follow the collar at their upper edges
+while retaining the original broad footprint on the flange. They stop before
+the four base screws. Vertical 19 mm washer and tool envelopes preserve access
+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.
 
 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