"""ISO 4762 (DIN 912) socket head cap screw. Envelope: head, hex socket and plain shank (no modelled thread).
The head sits on the XY plane at the origin; the shank points down -Z. `length` is measured under the head.

Material: property class 12.9 alloy steel, quenched and tempered (34CrNiMo6 from the material library), black oxide."""
from steve import Model

size = "M3"  # Thread size
length = 10  # mm Length under the head

# size: (head diameter dk, head height k, hex key s)
HEADS = {
    'M2': (3.8, 2.0, 1.5),
    'M2.5': (4.5, 2.5, 2.0),
    'M3': (5.5, 3.0, 2.5),
    'M4': (7.0, 4.0, 3.0),
    'M5': (8.5, 5.0, 4.0),
    'M6': (10.0, 6.0, 5.0),
    'M8': (13.0, 8.0, 6.0),
    'M10': (16.0, 10.0, 8.0),
    'M12': (18.0, 12.0, 10.0),
}
NOMINAL = {
    'M2': 2.0,
    'M2.5': 2.5,
    'M3': 3.0,
    'M4': 4.0,
    'M5': 5.0,
    'M6': 6.0,
    'M8': 8.0,
    'M10': 10.0,
    'M12': 12.0,
}
dk, k, s = HEADS[size]
d = NOMINAL[size]

model = Model()
with model.sketch("head_sketch", on="XY", name="Head") as sk:
    sk.circle("head", (0, 0), dk / 2)
model.extrude("head", "head_sketch", distance=k)
with model.sketch("shank_sketch", on="XY", name="Shank") as sk:
    sk.circle("shank", (0, 0), d / 2)
model.extrude("shank", "shank_sketch", distance=-length)
model.plane("head_top", on="XY", offset=k, name="Head top")
with model.sketch("socket_sketch", on="head_top", name="Hex socket") as sk:
    sk.polygon("hex", (0, 0), s / 2, 6, inscribed=False)
model.extrude("socket", "socket_sketch", distance=-0.55 * k, op="cut")
model.material("steel-34crnimo6")  # class 12.9 alloy steel
model.appearance(color="#2e3034", metalness=0.75, roughness=0.38)  # black oxide finish
result = model.result()