"""Trapezoidal lead screw envelope: a plain shaft at the major diameter d, axis along Z, centred on the origin. The
thread itself is not modelled, as in the library's threaded rods; `lead` only names the screw."""
from steve import Model

size = "Tr8"  # Nominal diameter
lead = 2  # mm Lead per turn
length = 300  # mm Length

# nominal: major diameter d. ISO 2904:2020 Table 1 (d of Tr10, Tr12, Tr16, with P and minor diameter d3 in the README);
# the Tr8 x 2, 4 and 8 screws are commercial (ISO 2904 tabulates Tr8 x 1.5): d = 8 is their designation.
SCREWS = {"Tr8": 8, "Tr10": 10, "Tr12": 12, "Tr16": 16}

d = SCREWS[size]
model = Model()
with model.sketch("section", on="XY", name="Section") as sk:
    sk.circle("outer", (0, 0), d / 2)
model.extrude("screw", "section", distance=length, both=True, name="Screw")
model.material("steel-generic", color="#b9bdc2")
result = model.result()