Recipes

Small, tested build123d functions for features that come up in almost every printed part, with the printing numbers behind them and their sources. Use one before improvising the feature: each recipe's demo part is built and run through check in the test suite.

from b123d_print.recipes import teardrop_hole, screw_hole, nut_trap, snap_arm

part -= Pos(0, 0, d.H) * screw_hole("M3", depth=d.H, head="counterbore", hole_comp=d.HOLE_COMP)
part -= Pos(10, 0, 6) * teardrop_hole(d.PIN_D + d.HOLE_COMP_H, length=30)

The AI reads them with the recipe(name) tool or the b123d-print://recipes/<name> resource (the code, a tested example, printing notes, sources); on the command line, b123d-print recipes [name].

Conventions

• Every dimension is a named parameter in mm; pass the script's Dims fields, never numbers from somewhere else.
• Cutters (holes, pockets, slots, text to deboss) open on Z=0 and go down, or are centered on their axis: part -= Pos(x, y, top) * nut_trap("M3"). Bodies (snap arm, hinges, lid, gusset) come in print orientation, bottom on Z=0.
• Hole diameters are the printed size: pass the user's hole compensation as hole_comp (d.HOLE_COMP, or d.HOLE_COMP_H for horizontal holes).
• Fits take the user's values: clearance=d.CLEARANCE, fit=d.PRESS_FIT, clearance=d.PIP_CLEARANCE for print-in-place.
• The BP-* ids point to the sourced rules in Design rules.

The recipes

Recipe	What	Functions	Summary
teardrop_hole	Teardrop / flat-roof horizontal hole	teardrop_hole	A horizontal hole along Y, centered on the origin, that prints without support: a circle
screw_hole	Counterbore and countersink	screw_hole	A vertical screw clearance hole (ISO 273 normal) with a counterbore for a socket head
keyhole_mount	Keyhole wall mount	keyhole_mount	Head entry and a retained shaft endpoint, with an optional continuous head cavity
mounting_slot	Adjustable screw mounting slot	mounting_slot	Round-ended shaft adjustment slot with optional opposite-face head recess
nut_trap	Hex nut trap	nut_trap	A captive hex nut pocket (ISO 4032 across flats + 2 x clearance; 0.1 per side, BP-T7) with
magnet_pocket	Magnet pocket	magnet_pocket	A round magnet pocket: diameter d + 2 x fit (per side; the user's press_fit, BP-F1) plus
pcb_standoff	PCB supports and reference boards	pcb_standoff, pcb_board, pcb_mounting_pattern	Explicit blind/through pilot, optional base flare, arbitrary board holes, exact sourced patterns
snap_arm	Snap-fit cantilever	snap_arm, snap_strain, snap_length	A cantilever snap arm lying flat (it bends in XY, along the layers, BP-N1), tapered from
living_hinge	Living hinge	living_hinge	Two leaves joined by a thin web thickness thick (0.4-0.6 mm, at least two lines, BP-N7)
pip_hinge	Print-in-place hinge	pip_hinge	A print-in-place hinge lying flat: two leaves (-Y and +Y) on the bed, knuckles along X
lid_with_lip	Lid with a lip and clearance	lid_with_lip, box_shell	A lid for a box outer_w x outer_l with walls wall thick: a plate top_t thick and a
text_label	Embossed and debossed text	text_label	Text as a solid from Z=0 up depth, centered on the origin. Emboss: part += Pos(x, y, top)
bed_chamfer	Fillet-safe chamfer on bed edges	bed_chamfer	Chamfer every edge on the bed (Z=0) by size at 45 degrees, holes included, by cutting a
zip_tie_slot	Cable and zip-tie slots	zip_tie_slot, cable_slot	A rectangular tunnel along X for a zip tie (width tie_w, thickness tie_t, + clearance per
gusset	Ribs and gussets	gusset, ribs	A triangular gusset in the XZ plane for an inside corner between a floor (Z=0, extending to

PCB supports and board stand-ins

pcb_standoff(height, outside_d, pilot_d, pilot_depth, flare=0, flare_h=0, hole_comp=0) returns a support with its base on Z=0 and the pilot opening upward at height. The remaining floor is height - pilot_depth; equal depth and height makes a through spacer. flare adds that much radius at the bottom, tapering to the shaft at flare_h; supply both or neither. Choose height from the measured underside components, solder joints and desired clearance. Check the wall (outside_d - pilot_d - HOLE_COMP) / 2 and remaining floor before printing.

Supply the target printed pilot_d and pass hole_comp=d.HOLE_COMP once. Plastic screw pilots depend on the screw, material and orientation; use the maker's guidance and a coupon. For a clearance spacer, reuse the selected hardware's existing dimensions:

from bd_warehouse.fastener import SocketHeadCapScrew
from b123d_print.recipes import pcb_standoff

screw = SocketHeadCapScrew("M2-0.4", 10, "iso4762", simple=True)
# d.SPACER_H, d.SPACER_D and d.HOLE_COMP are named fields in your script.
spacer = pcb_standoff(d.SPACER_H, d.SPACER_D,
                      screw.clearance_hole_diameters["Normal"], d.SPACER_H,
                      hole_comp=d.HOLE_COMP)

Metal tap_hole_diameters are tap drills, not automatic plastic pilot sizes. For a heat-set insert use its maker's hole and depth guidance; for enclosure screw clearance/counterbores, reuse screw_hole. These are printed supports, not models of purchased standoff hardware. Print base down, pilots vertical and open at the top; give bosses 3–4 or more perimeters (BP-T8).

pcb_board(width, length, thickness, holes, hole_d) returns a rectangular board stand-in. The datum is the board center in XY, its underside at Z=0; X spans width and Y spans length. Hole centers are (x, y) in that frame, viewed from above (+Z), and need not form a rectangle. An empty sequence gives a board without holes. Holes must be distinct and entirely within the board. hole_d is the actual board drill diameter and receives no printer compensation. The rectangular envelope excludes connectors, underside components and edge cutouts: add separate measured component volumes to assembly(d).

pcb_mounting_pattern(model) provides two exact manufacturer patterns, also available as b123d_print.pcb.PCB_PATTERNS. The frozen record contains model, width, length, holes, hole_d, datum and source. Thickness and component keep-outs must be supplied separately. Unknown model keys raise ValueError; there is no universal ESP32 pattern.

Exact model key	Board envelope X × Y	Hole centers from board center	Hole diameter	Top-view axes and source
raspberry_pi_zero_v1_2	65 × 30	(±29, ±11.5)	2.75	+X away from microSD; +Y toward GPIO. RPI-ZERO-V1_2 drawing, 2015-09-23
raspberry_pi_pico_rev3	21 × 51	(±5.7, ±23.5)	2.1	+Y toward micro-USB; +X right on component-side view. RP2040 Pico Rev3 datasheet, chapter 2, product brief drawing

All table dimensions are mm. These records describe only those boards/drawings; compare your actual board before using one. For example, p = pcb_mounting_pattern("raspberry_pi_pico_rev3") then pcb_board(p.width, p.length, d.PCB_T, p.holes, p.hole_d) preserves its center datum.

Compose an enclosure and check the underside

This digital fixture illustrates an asymmetric three-hole board; the values are illustrative, not a newly printed example. The already printed esp_ir_blaster is the physical workflow reference. The standoff recipe's demo and these tests establish geometry, not physical fit.

from dataclasses import dataclass
from build123d import Align, Box, Pos
from b123d_print import Mates, Template, Wall, hole_comp
from b123d_print.recipes import box_shell, pcb_board, pcb_standoff

@dataclass(frozen=True)
class Dims:
    BOX_W: float = 48.0  # illustrative envelope
    BOX_L: float = 36.0  # illustrative envelope
    BOX_H: float = 12.0  # illustrative height
    WALL: float = 2.0  # illustrative wall
    FLOOR: float = 2.0  # illustrative floor
    PCB_W: float = 34.0  # replace with measured board width
    PCB_L: float = 24.0  # replace with measured board length
    PCB_T: float = 1.6  # replace with measured board thickness
    HOLES: tuple = ((-13.0, -7.0), (12.0, -7.0), (-10.0, 8.0))  # measured center coordinates
    PCB_HOLE_D: float = 3.4  # replace with actual board holes
    SUPPORT_H: float = 5.0  # chosen underside clearance above floor
    SUPPORT_D: float = 7.0  # chosen boss outside diameter
    PILOT_D: float = 2.5  # illustrative pilot; verify screw/material with a coupon
    PILOT_DEPTH: float = 4.0  # leaves 1 mm within support, plus box floor
    FLARE: float = 1.0  # extra base radius
    FLARE_H: float = 1.0  # base flare height
    UNDER_W: float = 8.0  # replace with measured underside component envelope
    UNDER_L: float = 6.0  # replace with measured envelope
    UNDER_H: float = 3.0  # component extends below board at its center
    TEMPLATE_T: float = 1.2  # existing template default
    MIN_SUPPORT_WALL: float = 1.6  # chosen wall minimum
    HOLE_COMP: float = hole_comp(__file__)  # your printer calibration

    @property
    def PCB_Z(self):
        return self.FLOOR + self.SUPPORT_H


def base(d):
    part = box_shell(d.BOX_W, d.BOX_L, d.BOX_H, wall=d.WALL, floor=d.FLOOR)
    for x, y in d.HOLES:
        part += Pos(x, y, d.FLOOR) * pcb_standoff(
            d.SUPPORT_H, d.SUPPORT_D, d.PILOT_D, d.PILOT_DEPTH,
            flare=d.FLARE, flare_h=d.FLARE_H, hole_comp=d.HOLE_COMP)
    return part


def build(d):
    return {"base": lambda: base(d)}


def assembly(d):
    board = Pos(0, 0, d.PCB_Z) * pcb_board(d.PCB_W, d.PCB_L, d.PCB_T, d.HOLES, d.PCB_HOLE_D)
    underside = Pos(0, 0, d.PCB_Z - d.UNDER_H) * Box(
        d.UNDER_W, d.UNDER_L, d.UNDER_H,
        align=(Align.CENTER, Align.CENTER, Align.MIN))
    return [(base(d), None, "base"), (board, None, "board (stand-in)"),
            (underside, None, "underside component (stand-in)")]


def checks(d):
    return [Mates(), Wall("base", "XY", d.FLOOR + d.SUPPORT_H / 2,
                         near=d.HOLES[0], radius=d.SUPPORT_D / 2,
                         min=d.MIN_SUPPORT_WALL, frame="assembly", label="PCB pilot")]


def templates(d):
    return [Template.slice("XY", d.PCB_Z - d.TEMPLATE_T / 2,
                           part="base", name="pcb_supports", thickness=d.TEMPLATE_T)]

Run b123d-print fit <name> or the check_fit tool: the board contacts its supports without interference. Moving a support under the central component produces an interference finding; resolve it by changing the design. The check never removes material automatically.

Inspect the highlighted template region with make_template before printing. The slice joins separate supports with the existing thin base and preserves their spacing. Set the board on it and try the intended screws to check hole position and printed diameter. It does not verify standoff height, component clearance, full enclosure fit or long-term screw strength. Measure and physically validate the fit before printing the full enclosure or publishing it as a printed example.

Sources

The printing numbers come from the sourced design rules (holes BP-H, overhangs BP-O, fits BP-F, snap fits and hinges BP-N, screws and nuts BP-T, text BP-X, ribs BP-R, bed edges BP-B), and for screw and nut sizes from ISO 273 (clearance holes), ISO 4762 (socket head cap screws), ISO 10642 (countersunk screws) and ISO 4032 (hex nuts); the screw hole recipe reads its sizes from bd_warehouse's fastener tables (see Threads, fasteners and gears). The snap-arm strain formulas are from Bayer MaterialScience's Snap-Fit Joints for Plastics design guide; the allowable strains are provisional (one source, BP-N4): say they are estimates.

Wall mounts and adjustable screw slots

keyhole_mount and mounting_slot cut flat plates for light enclosure mounting. Their geometry is checked in CAD; the fixture below has not been physically printed or load tested. Neither recipe specifies wall anchors, a safe load, vibration retention or a certified strength rating.

Both take shaft_d, head_d, plate_t, travel, head_depth, clearance, hole_comp, size and min_lip. All dimensions are mm. Omitted diameters come from _screw(size): bd_warehouse's ISO 273 Normal clearance and ISO 4762 socket-head tables, with the existing SCREW fallback. Explicit shaft_d is the base opening diameter (use the measured shaft for a custom fit), and head_d is the measured maximum head diameter, including any washer that must pass. Do not assume a pan head has socket-head dimensions. Use size=None with both explicit diameters for other metric or inch screws; convert inch measurements to mm.

The cutter adds 2 × clearance per diameter (clearance is per side) and then adds hole_comp once per diameter (total). Table clearance holes already have an allowance: clearance adds extra to that base, so set it to zero to keep the table's shaft clearance. Do not pre-add HOLE_COMP or also enable slicer hole compensation. The actual head must remain larger than the compensated shaft opening; excessive allowances are rejected. head_depth is an axial dimension with no diameter compensation: leave axial space for the measured head height.

from build123d import Pos, Rot
from b123d_print.recipes import keyhole_mount, mounting_slot

# Insert at (x, y), then the screw moves +Y relative to the plate by TRAVEL.
part -= Pos(d.X, d.Y, d.PLATE_T) * keyhole_mount(
    shaft_d=d.SHAFT_D, head_d=d.HEAD_D, size=None, plate_t=d.PLATE_T,
    travel=d.TRAVEL, head_depth=d.HEAD_DEPTH, clearance=d.CLEARANCE,
    hole_comp=d.HOLE_COMP, min_lip=d.MIN_LIP)
# Rotate +90 degrees around Z: screw travel becomes -X.
part -= Pos(d.OTHER_X, d.Y, d.PLATE_T) * Rot(0, 0, 90) * mounting_slot(
    size="M3", plate_t=d.PLATE_T, travel=d.TRAVEL, hole_comp=d.HOLE_COMP)

The origin is the head entry center (keyhole_mount) or first shaft center (mounting_slot), at the insertion face Z=0. The cutter ends at Z=-plate_t. Shaft center travel is from Y=0 to Y=travel; overall slot length also includes its round ends. For a hanging plate, choose the orientation so gravity moves the plate opposite this relative screw motion. A mounting_slot has no head entry: insert the screw axially before tightening it, and loosen it to adjust the position. It is not a freely captive slide.

With head_depth=0, a keyhole head passes through the entry and remains proud of the opposite face; provide room for it behind that face. With head_depth>0, a head-sized recess opens from the opposite face at Z=-plate_t, up toward Z=0, continuously along the entire travel. This is not a counterbore on the insertion face. The lip next to Z=0 is plate_t-head_depth thick. min_lip is a project-chosen minimum for that axial thickness; its default zero only rejects a vanished lip. Also inspect the radial overlap (actual head diameter - compensated shaft width)/2 and the material between the recess and the plate edges. Positive thickness alone says nothing about load capacity. A head cavity opening downward in print orientation creates a roof under the lip; orient the cavity upward where possible, and run the overhang/bridge checks otherwise.

Two-screw fit coupon

Download the CAD-only coupon source and copy it into parts/wall_mount_coupon/wall_mount_coupon.py. It uses two M3 ISO 4762 socket heads at 30 mm center spacing, 10 mm center travel, a 5 mm plate, and a 3.4 mm head cavity leaving 1.6 mm axial lip. These are chosen fixture dimensions, not a mounting standard. Measure your actual screws and set the Dims fields first. The script uses your clearance and hole compensation.

uv run parts/wall_mount_coupon/wall_mount_coupon.py --formats 3mf,png
b123d-print check wall_mount_coupon
b123d-print fit wall_mount_coupon
b123d-print view wall_mount_coupon --assembly

The saved views and these sections come from the actual coupon CAD, with the cavity facing up in print orientation. The center section shows the lip depth; the XY section through that lip shows the two entry/retention profiles.

Inspect the Wall result in assembly coordinates near the retained screw endpoint and verify that it measured the lip. assembly(d) supplies two screw stand-ins at retained positions for fit; it also gives the positions for inspecting head insertion and travel in sections. The regression tests sweep representative head/shaft positions through entry and travel and confirm that pulling the head through the narrow lip collides. Tighten the screws to hold the final position; keyholes alone do not prevent reverse travel or lifting off.

The fixture's templates(d) exports a full-depth crop with the normal export tools. Print that small coupon with the same orientation, material, layer height and hole settings planned for the mount. If the exporter warns that hole compensation has never been calibrated, print the existing hole_coupon and store its result before judging the mounting fit. A thin face/slice template can check the 30 mm pattern and entry diameter, but cannot check recess depth, head travel or lip retention. Try both screws, head insertion, the full slide, seating and removal without forcing it. Record screw measurements, printer/material, allowances and the physical result. A maintainer must print and try this fixture before adding it as a physically validated bundled example; no such validation is claimed here.

Which dimensions are standardized?

ISO 273 specifies clearance-hole diameters, and ISO 4762 specifies metric socket-head cap screws. ASME B18.3 covers inch-series socket cap/shoulder/set screws and includes related drill/counterbore data. Those fastener dimensions are distinct from this recipe's head entry, travel, spacing and lip. The recipes do not claim a universal ISO/ASME keyhole-mount layout or an ASME inch-size table; use explicitly measured dimensions for unsupported hardware.