"""ISO 4017 (DIN 933) hex head screw, fully threaded. Envelope: hex head and plain shank.
The head's bearing face is on the XY plane at the origin; the shank points down -Z."""
from steve import Model

size = "M6"  # Thread size
length = 20  # mm Length under the head

# size: (across flats s, head height k)
HEADS = {
    'M3': (5.5, 2.0),
    'M4': (7.0, 2.8),
    'M5': (8.0, 3.5),
    'M6': (10.0, 4.0),
    'M8': (13.0, 5.3),
    'M10': (16.0, 6.4),
    'M12': (18.0, 7.5),
}
NOMINAL = {
    'M3': 3.0,
    'M4': 4.0,
    'M5': 5.0,
    'M6': 6.0,
    'M8': 8.0,
    'M10': 10.0,
    'M12': 12.0,
}
s, k = HEADS[size]
d = NOMINAL[size]

model = Model()
with model.sketch("head_sketch", on="XY", name="Head") as sk:
    sk.polygon("hex", (0, 0), s / 2, 6, inscribed=False)
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)
result = model.result()