steve/spring-lock-washer

Metric curved spring washers (DIN 137 A) and external tooth lock washers (DIN 6797 A), M2 to M10.

v1.0.0 Latest STEVE MIT 1

Open in STEVE

Isometric

Parameters

Preset15 sizes

Screw size8 options

Style

curvedtooth

curved: DIN 137 A (M2 to M10); tooth: DIN 6797 A external teeth (M2 to M8).

Material2 options

Defaults built

part.py 44 lines · Python · STEVE runtime · checked

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"""Metric spring and lock washers: DIN 137 form A curved spring washers and DIN 6797 form A external tooth lock

washers.

- curved (DIN 137 A): the annulus d1 x d2, s thick, curved about the X axis so that it stands h (max, the free height)

tall: the region of the annulus between two coaxial cylinders (axis parallel to X) of radii R and R + s, with R

chosen so that the inner surface rises h - s at the rim. Its lowest point is on the XY plane at the origin.

- tooth (DIN 6797 A): envelope, the flat blank, an annulus d1 x d2, s thick, on the XY plane; the standard gives the

number of teeth (6 or 8) and the overall height (at least 2 s) but not the teeth's shape, so they are not modelled.

Centred on the origin.

"""

from steve import Model

size = "M4" # Nominal size (screw)

style = "curved" # Washer style

material = "spring-steel" # Material

# mm. DIN 137 (1985) form A, curved: (d1 min = nominal, d2 nominal, s nominal, h max)

CURVED = {"M2": (2.2, 4.5, 0.3, 1.0), "M2.5": (2.8, 5.5, 0.3, 1.1), "M3": (3.2, 6, 0.4, 1.3), "M4": (4.3, 8, 0.5, 1.6),

"M5": (5.3, 10, 0.5, 1.8), "M6": (6.4, 11, 0.5, 2.2), "M8": (8.4, 15, 0.5, 3.4), "M10": (10.5, 18, 0.8, 4.0)}

# mm. DIN 6797:1988-07 form A, external teeth: (d1 min = nominal, d2 max = nominal, s nominal, number of teeth)

TOOTH = {"M2": (2.2, 4.5, 0.3, 6), "M2.5": (2.7, 5.5, 0.4, 6), "M3": (3.2, 6, 0.4, 6), "M4": (4.3, 8, 0.5, 8),

"M5": (5.3, 10, 0.6, 8), "M6": (6.4, 11, 0.7, 8), "M8": (8.4, 15, 0.8, 8)}

MATERIALS = {"spring-steel": ("steel-generic", "#4a4c50"), "stainless": ("stainless-304", "#c9ccd0")}

material_id, colour = MATERIALS[material]

model = Model()

if style == "curved":

d1, d2, s, h = CURVED[size]

r2, k = d2 / 2, h - s

R = (r2 * r2 + k * k) / (2 * k) # inner surface radius: it rises k at y = +-d2/2

model.cylinder("blank", r2, h + 2, at=(0, 0, -1), name="Blank")

model.cylinder("hole", d1 / 2, h + 2, at=(0, 0, -1), op="cut", name="Hole")

model.cylinder("shell", R + s, 2 * d2, at=(-d2, 0, R + s), direction=(1, 0, 0), op="new", name="Shell")

model.cylinder("shell_in", R, 2 * d2, at=(-d2, 0, R + s), direction=(1, 0, 0), op="cut", body="shell", name="Shell inside")

model.combine("washer", "blank", ["shell"], op="intersect", name="Washer")

else:

d1, d2, s, teeth = TOOTH[size]

with model.sketch("washer_sketch", on="XY", name="Washer") as sk:

sk.circle("outside", (0, 0), d2 / 2)

sk.circle("inside", (0, 0), d1 / 2)

model.extrude("washer", "washer_sketch", distance=s, name="Washer")

model.material(material_id, color=colour)

result = model.result()

"""Metric spring and lock washers: DIN 137 form A curved spring washers and DIN 6797 form A external tooth lock
washers.

- curved (DIN 137 A): the annulus d1 x d2, s thick, curved about the X axis so that it stands h (max, the free height)
  tall: the region of the annulus between two coaxial cylinders (axis parallel to X) of radii R and R + s, with R
  chosen so that the inner surface rises h - s at the rim. Its lowest point is on the XY plane at the origin.
- tooth (DIN 6797 A): envelope, the flat blank, an annulus d1 x d2, s thick, on the XY plane; the standard gives the
  number of teeth (6 or 8) and the overall height (at least 2 s) but not the teeth's shape, so they are not modelled.
Centred on the origin.
"""
from steve import Model

size = "M4"  # Nominal size (screw)
style = "curved"  # Washer style
material = "spring-steel"  # Material

# mm. DIN 137 (1985) form A, curved: (d1 min = nominal, d2 nominal, s nominal, h max)
CURVED = {"M2": (2.2, 4.5, 0.3, 1.0), "M2.5": (2.8, 5.5, 0.3, 1.1), "M3": (3.2, 6, 0.4, 1.3), "M4": (4.3, 8, 0.5, 1.6),
          "M5": (5.3, 10, 0.5, 1.8), "M6": (6.4, 11, 0.5, 2.2), "M8": (8.4, 15, 0.5, 3.4), "M10": (10.5, 18, 0.8, 4.0)}
# mm. DIN 6797:1988-07 form A, external teeth: (d1 min = nominal, d2 max = nominal, s nominal, number of teeth)
TOOTH = {"M2": (2.2, 4.5, 0.3, 6), "M2.5": (2.7, 5.5, 0.4, 6), "M3": (3.2, 6, 0.4, 6), "M4": (4.3, 8, 0.5, 8),
         "M5": (5.3, 10, 0.6, 8), "M6": (6.4, 11, 0.7, 8), "M8": (8.4, 15, 0.8, 8)}
MATERIALS = {"spring-steel": ("steel-generic", "#4a4c50"), "stainless": ("stainless-304", "#c9ccd0")}

material_id, colour = MATERIALS[material]
model = Model()
if style == "curved":
    d1, d2, s, h = CURVED[size]
    r2, k = d2 / 2, h - s
    R = (r2 * r2 + k * k) / (2 * k)      # inner surface radius: it rises k at y = +-d2/2
    model.cylinder("blank", r2, h + 2, at=(0, 0, -1), name="Blank")
    model.cylinder("hole", d1 / 2, h + 2, at=(0, 0, -1), op="cut", name="Hole")
    model.cylinder("shell", R + s, 2 * d2, at=(-d2, 0, R + s), direction=(1, 0, 0), op="new", name="Shell")
    model.cylinder("shell_in", R, 2 * d2, at=(-d2, 0, R + s), direction=(1, 0, 0), op="cut", body="shell", name="Shell inside")
    model.combine("washer", "blank", ["shell"], op="intersect", name="Washer")
else:
    d1, d2, s, teeth = TOOTH[size]
    with model.sketch("washer_sketch", on="XY", name="Washer") as sk:
        sk.circle("outside", (0, 0), d2 / 2)
        sk.circle("inside", (0, 0), d1 / 2)
    model.extrude("washer", "washer_sketch", distance=s, name="Washer")
model.material(material_id, color=colour)
result = model.result()

pypart.toml 136 lines · TOML

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name = "steve/spring-lock-washer"

version = "1.0.0"

runtime = "steve"

license = "MIT"

summary = "Metric curved spring washers (DIN 137 A) and external tooth lock washers (DIN 6797 A), M2 to M10."

description = """Curved spring washers, DIN 137 form A (M2 to M10): the annulus curved about one axis to its free height \

h max. External tooth lock washers, DIN 6797 form A (M2 to M8): envelope geometry, the flat blank (the teeth's shape \

is not given by the standard).

Centred on the origin, lying on the XY plane. Dimensions: see the README."""

tags = ["fastener", "washer", "spring-washer", "curved-washer", "tooth-lock-washer", "din-137", "din-6797", "metric"]

[parameters.size]

type = "choice"

default = "M4"

choices = ["M2", "M2.5", "M3", "M4", "M5", "M6", "M8", "M10"]

label = "Screw size"

[parameters.style]

type = "choice"

default = "curved"

choices = ["curved", "tooth"]

label = "Style"

description = "curved: DIN 137 A (M2 to M10); tooth: DIN 6797 A external teeth (M2 to M8)."

[parameters.material]

type = "choice"

default = "spring-steel"

choices = ["spring-steel", "stainless"]

label = "Material"

[[presets]]

id = "DIN137A-M2"

title = "Curved spring washer M2 (DIN 137 A)"

params = { size = "M2", style = "curved" }

aliases = ["DIN 137 A M2", "DIN 137 M2", "curved spring washer M2", "DIN 137A M2"]

standard = "DIN 137 A"

[[presets]]

id = "DIN137A-M2.5"

title = "Curved spring washer M2.5 (DIN 137 A)"

params = { size = "M2.5", style = "curved" }

aliases = ["DIN 137 A M2.5", "DIN 137 M2.5", "curved spring washer M2.5", "DIN 137A M2.5"]

standard = "DIN 137 A"

[[presets]]

id = "DIN137A-M3"

title = "Curved spring washer M3 (DIN 137 A)"

params = { size = "M3", style = "curved" }

aliases = ["DIN 137 A M3", "DIN 137 M3", "curved spring washer M3", "DIN 137A M3"]

standard = "DIN 137 A"

[[presets]]

id = "DIN137A-M4"

title = "Curved spring washer M4 (DIN 137 A)"

params = { size = "M4", style = "curved" }

aliases = ["DIN 137 A M4", "DIN 137 M4", "curved spring washer M4", "DIN 137A M4"]

standard = "DIN 137 A"

[[presets]]

id = "DIN137A-M5"

title = "Curved spring washer M5 (DIN 137 A)"

params = { size = "M5", style = "curved" }

aliases = ["DIN 137 A M5", "DIN 137 M5", "curved spring washer M5", "DIN 137A M5"]

standard = "DIN 137 A"

[[presets]]

id = "DIN137A-M6"

title = "Curved spring washer M6 (DIN 137 A)"

params = { size = "M6", style = "curved" }

aliases = ["DIN 137 A M6", "DIN 137 M6", "curved spring washer M6", "DIN 137A M6"]

standard = "DIN 137 A"

[[presets]]

id = "DIN137A-M8"

title = "Curved spring washer M8 (DIN 137 A)"

params = { size = "M8", style = "curved" }

aliases = ["DIN 137 A M8", "DIN 137 M8", "curved spring washer M8", "DIN 137A M8"]

standard = "DIN 137 A"

[[presets]]

id = "DIN137A-M10"

title = "Curved spring washer M10 (DIN 137 A)"

params = { size = "M10", style = "curved" }

aliases = ["DIN 137 A M10", "DIN 137 M10", "curved spring washer M10", "DIN 137A M10"]

standard = "DIN 137 A"

[[presets]]

id = "DIN6797A-M2"

title = "External tooth lock washer M2 (DIN 6797 A)"

params = { size = "M2", style = "tooth" }

aliases = ["DIN 6797 A M2", "DIN 6797 M2", "external tooth lock washer M2", "star washer M2"]

standard = "DIN 6797 A"

[[presets]]

id = "DIN6797A-M2.5"

title = "External tooth lock washer M2.5 (DIN 6797 A)"

params = { size = "M2.5", style = "tooth" }

aliases = ["DIN 6797 A M2.5", "DIN 6797 M2.5", "external tooth lock washer M2.5", "star washer M2.5"]

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standard = "DIN 6797 A"

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[[presets]]

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id = "DIN6797A-M3"

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title = "External tooth lock washer M3 (DIN 6797 A)"

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params = { size = "M3", style = "tooth" }

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aliases = ["DIN 6797 A M3", "DIN 6797 M3", "external tooth lock washer M3", "star washer M3"]

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standard = "DIN 6797 A"

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[[presets]]

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id = "DIN6797A-M4"

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title = "External tooth lock washer M4 (DIN 6797 A)"

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params = { size = "M4", style = "tooth" }

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aliases = ["DIN 6797 A M4", "DIN 6797 M4", "external tooth lock washer M4", "star washer M4"]

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standard = "DIN 6797 A"

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[[presets]]

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id = "DIN6797A-M5"

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title = "External tooth lock washer M5 (DIN 6797 A)"

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params = { size = "M5", style = "tooth" }

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aliases = ["DIN 6797 A M5", "DIN 6797 M5", "external tooth lock washer M5", "star washer M5"]

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standard = "DIN 6797 A"

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[[presets]]

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id = "DIN6797A-M6"

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title = "External tooth lock washer M6 (DIN 6797 A)"

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params = { size = "M6", style = "tooth" }

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aliases = ["DIN 6797 A M6", "DIN 6797 M6", "external tooth lock washer M6", "star washer M6"]

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standard = "DIN 6797 A"

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[[presets]]

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id = "DIN6797A-M8"

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title = "External tooth lock washer M8 (DIN 6797 A)"

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params = { size = "M8", style = "tooth" }

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aliases = ["DIN 6797 A M8", "DIN 6797 M8", "external tooth lock washer M8", "star washer M8"]

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standard = "DIN 6797 A"

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name = "steve/spring-lock-washer"
version = "1.0.0"
runtime = "steve"
license = "MIT"
summary = "Metric curved spring washers (DIN 137 A) and external tooth lock washers (DIN 6797 A), M2 to M10."
description = """Curved spring washers, DIN 137 form A (M2 to M10): the annulus curved about one axis to its free height \
h max. External tooth lock washers, DIN 6797 form A (M2 to M8): envelope geometry, the flat blank (the teeth's shape \
is not given by the standard).

Centred on the origin, lying on the XY plane. Dimensions: see the README."""
tags = ["fastener", "washer", "spring-washer", "curved-washer", "tooth-lock-washer", "din-137", "din-6797", "metric"]

[parameters.size]
type = "choice"
default = "M4"
choices = ["M2", "M2.5", "M3", "M4", "M5", "M6", "M8", "M10"]
label = "Screw size"

[parameters.style]
type = "choice"
default = "curved"
choices = ["curved", "tooth"]
label = "Style"
description = "curved: DIN 137 A (M2 to M10); tooth: DIN 6797 A external teeth (M2 to M8)."

[parameters.material]
type = "choice"
default = "spring-steel"
choices = ["spring-steel", "stainless"]
label = "Material"

[[presets]]
id = "DIN137A-M2"
title = "Curved spring washer M2 (DIN 137 A)"
params = { size = "M2", style = "curved" }
aliases = ["DIN 137 A M2", "DIN 137 M2", "curved spring washer M2", "DIN 137A M2"]
standard = "DIN 137 A"

[[presets]]
id = "DIN137A-M2.5"
title = "Curved spring washer M2.5 (DIN 137 A)"
params = { size = "M2.5", style = "curved" }
aliases = ["DIN 137 A M2.5", "DIN 137 M2.5", "curved spring washer M2.5", "DIN 137A M2.5"]
standard = "DIN 137 A"

[[presets]]
id = "DIN137A-M3"
title = "Curved spring washer M3 (DIN 137 A)"
params = { size = "M3", style = "curved" }
aliases = ["DIN 137 A M3", "DIN 137 M3", "curved spring washer M3", "DIN 137A M3"]
standard = "DIN 137 A"

[[presets]]
id = "DIN137A-M4"
title = "Curved spring washer M4 (DIN 137 A)"
params = { size = "M4", style = "curved" }
aliases = ["DIN 137 A M4", "DIN 137 M4", "curved spring washer M4", "DIN 137A M4"]
standard = "DIN 137 A"

[[presets]]
id = "DIN137A-M5"
title = "Curved spring washer M5 (DIN 137 A)"
params = { size = "M5", style = "curved" }
aliases = ["DIN 137 A M5", "DIN 137 M5", "curved spring washer M5", "DIN 137A M5"]
standard = "DIN 137 A"

[[presets]]
id = "DIN137A-M6"
title = "Curved spring washer M6 (DIN 137 A)"
params = { size = "M6", style = "curved" }
aliases = ["DIN 137 A M6", "DIN 137 M6", "curved spring washer M6", "DIN 137A M6"]
standard = "DIN 137 A"

[[presets]]
id = "DIN137A-M8"
title = "Curved spring washer M8 (DIN 137 A)"
params = { size = "M8", style = "curved" }
aliases = ["DIN 137 A M8", "DIN 137 M8", "curved spring washer M8", "DIN 137A M8"]
standard = "DIN 137 A"

[[presets]]
id = "DIN137A-M10"
title = "Curved spring washer M10 (DIN 137 A)"
params = { size = "M10", style = "curved" }
aliases = ["DIN 137 A M10", "DIN 137 M10", "curved spring washer M10", "DIN 137A M10"]
standard = "DIN 137 A"

[[presets]]
id = "DIN6797A-M2"
title = "External tooth lock washer M2 (DIN 6797 A)"
params = { size = "M2", style = "tooth" }
aliases = ["DIN 6797 A M2", "DIN 6797 M2", "external tooth lock washer M2", "star washer M2"]
standard = "DIN 6797 A"

[[presets]]
id = "DIN6797A-M2.5"
title = "External tooth lock washer M2.5 (DIN 6797 A)"
params = { size = "M2.5", style = "tooth" }
aliases = ["DIN 6797 A M2.5", "DIN 6797 M2.5", "external tooth lock washer M2.5", "star washer M2.5"]
standard = "DIN 6797 A"

[[presets]]
id = "DIN6797A-M3"
title = "External tooth lock washer M3 (DIN 6797 A)"
params = { size = "M3", style = "tooth" }
aliases = ["DIN 6797 A M3", "DIN 6797 M3", "external tooth lock washer M3", "star washer M3"]
standard = "DIN 6797 A"

[[presets]]
id = "DIN6797A-M4"
title = "External tooth lock washer M4 (DIN 6797 A)"
params = { size = "M4", style = "tooth" }
aliases = ["DIN 6797 A M4", "DIN 6797 M4", "external tooth lock washer M4", "star washer M4"]
standard = "DIN 6797 A"

[[presets]]
id = "DIN6797A-M5"
title = "External tooth lock washer M5 (DIN 6797 A)"
params = { size = "M5", style = "tooth" }
aliases = ["DIN 6797 A M5", "DIN 6797 M5", "external tooth lock washer M5", "star washer M5"]
standard = "DIN 6797 A"

[[presets]]
id = "DIN6797A-M6"
title = "External tooth lock washer M6 (DIN 6797 A)"
params = { size = "M6", style = "tooth" }
aliases = ["DIN 6797 A M6", "DIN 6797 M6", "external tooth lock washer M6", "star washer M6"]
standard = "DIN 6797 A"

[[presets]]
id = "DIN6797A-M8"
title = "External tooth lock washer M8 (DIN 6797 A)"
params = { size = "M8", style = "tooth" }
aliases = ["DIN 6797 A M8", "DIN 6797 M8", "external tooth lock washer M8", "star washer M8"]
standard = "DIN 6797 A"

README.md 56 lines · Markdown

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Spring and lock washers (DIN 137 A / DIN 6797 A)

Curved spring washers (DIN 137 form A, M2 to M10) and external tooth lock washers (DIN 6797 form A, M2 to M8). Presets cover the catalogue's metric curved spring washers and external tooth lock washers.

Geometry

curved (DIN 137 A): the annulus d1 × d2, s thick, curved about an axis parallel to X so that it stands h (max, the free height) tall: the part of the annulus between two coaxial cylinders of radii R and R + s, R chosen so that the inner (upper) surface rises h − s at the rim (R = ((d2/2)² + (h − s)²) / (2 (h − s))). Its lowest point is on the XY plane at the origin. The standard gives d1, d2, s and h only; this is the curved form those four numbers define.
tooth (DIN 6797 A): envelope, the flat blank, an annulus d1 × d2, s thick, lying on the XY plane. The standard gives the number of teeth (6 up to M3, 8 from M4) and the overall height (at least 2 s) but not the teeth's shape, width or twist, so the teeth are not modelled.

Parameters

Parameter	Meaning
`size`	Screw size: M2 to M10 (curved), M2 to M8 (tooth)
`style`	`curved` (DIN 137 A) or `tooth` (DIN 6797 A)
`material`	`spring-steel` or `stainless`

Sources

DIN 137 (1985; withdrawn without replacement), Spring washers, curved or waved, form A, as reproduced by fasten.it (https://fasten.it/en/Norms/Norm/DIN%20137, table "source DIN 137 A"). Cross-check: McMaster-Carr's DIN 137A washer specifications (https://mcmaster.com/products/washers/specifications-met~din-137a) agree on d1, d2, s and h max for M2, M3, M4, M5, M6, M8 and M10. Disagreement: the fasten.it page's text calls form A "waved" and form B "curved"; its figure, DIN 137 itself (form A gewölbt, form B gewellt) and McMaster have form A curved. The table used here is the one with h max 1.0 (M2) to 4.0 (M10), which McMaster sells as DIN 137 A curved washers.
DIN 6797:1988-07 (withdrawn), Toothed lock washers, form A (external teeth), as reproduced by fasten.it (https://fasten.it/en/Norms/Norm/DIN%206797). Cross-checks: Bossard BN 787 "Toothed lock washers type A, external teeth" (28 Apr 2017) agrees on every d1, d2, s; Duratool/Farnell datasheet V1.1 (21/07/17, https://www.farnell.com/cad/2337766.pdf) agrees on the teeth (M3 6, M4 8). The rows "for hexagon screws only" (M5 5.1/9, M8 8.2/14) are not used.

Size	Curved d1	d2	s	h max	Tooth d1	d2	s	teeth
M2	2.2	4.5	0.3	1.0	2.2	4.5	0.3	6
M2.5	2.8	5.5	0.3	1.1	2.7	5.5	0.4	6
M3	3.2	6	0.4	1.3	3.2	6	0.4	6
M4	4.3	8	0.5	1.6	4.3	8	0.5	8
M5	5.3	10	0.5	1.8	5.3	10	0.6	8
M6	6.4	11	0.5	2.2	6.4	11	0.7	8
M8	8.4	15	0.5	3.4	8.4	15	0.8	8
M10	10.5	18	0.8	4.0	–	–	–	–

The catalogue's entries carry DIN 125 plain-washer dimensions (for example M3: 3.2 / 7 / 0.5), not a curved or toothed washer's; the presets follow the standards. Not covered: M12 curved (DIN 137 A has no M12); wave washers (DIN 137 B gives no number of waves).

Preset list: sizes of the step.parts catalogue (MIT), see library/NOTICE.md.

# Spring and lock washers (DIN 137 A / DIN 6797 A)

Curved spring washers (DIN 137 form A, M2 to M10) and external tooth lock washers (DIN 6797 form A, M2 to M8).

Presets cover the catalogue's metric curved spring washers and external tooth lock washers.

## Geometry

- **curved** (DIN 137 A): the annulus **d1** × **d2**, **s** thick, curved about an axis parallel to X so that it

stands **h** (max, the free height) tall: the part of the annulus between two coaxial cylinders of radii R and

R + s, R chosen so that the inner (upper) surface rises h − s at the rim (R = ((d2/2)² + (h − s)²) / (2 (h − s))).

Its lowest point is on the XY plane at the origin. The standard gives d1, d2, s and h only; this is the curved form

those four numbers define.

- **tooth** (DIN 6797 A): envelope, the flat blank, an annulus d1 × d2, s thick, lying on the XY plane. The standard

gives the number of teeth (6 up to M3, 8 from M4) and the overall height (at least 2 s) but not the teeth's shape,

width or twist, so the teeth are not modelled.

## Parameters

| Parameter | Meaning |

|---|---|

| `size` | Screw size: M2 to M10 (curved), M2 to M8 (tooth) |

| `style` | `curved` (DIN 137 A) or `tooth` (DIN 6797 A) |

| `material` | `spring-steel` or `stainless` |

## Sources

- **DIN 137** (1985; withdrawn without replacement), *Spring washers, curved or waved*, form A, as reproduced by

fasten.it (https://fasten.it/en/Norms/Norm/DIN%20137, table "source DIN 137 A"). Cross-check: McMaster-Carr's DIN

137A washer specifications (https://mcmaster.com/products/washers/specifications-met~din-137a) agree on d1, d2, s

and h max for M2, M3, M4, M5, M6, M8 and M10.

Disagreement: the fasten.it page's text calls form A "waved" and form B "curved"; its figure, DIN 137 itself

(form A gewölbt, form B gewellt) and McMaster have form A curved. The table used here is the one with h max 1.0 (M2)

to 4.0 (M10), which McMaster sells as DIN 137 A curved washers.

- **DIN 6797:1988-07** (withdrawn), *Toothed lock washers*, form A (external teeth), as reproduced by fasten.it

(https://fasten.it/en/Norms/Norm/DIN%206797). Cross-checks: Bossard BN 787 "Toothed lock washers type A, external

teeth" (28 Apr 2017) agrees on every d1, d2, s; Duratool/Farnell datasheet V1.1 (21/07/17,

https://www.farnell.com/cad/2337766.pdf) agrees on the teeth (M3 6, M4 8). The rows "for hexagon screws only" (M5

5.1/9, M8 8.2/14) are not used.

| Size | Curved d1 | d2 | s | h max | Tooth d1 | d2 | s | teeth |

|---|---|---|---|---|---|---|---|---|

| M2 | 2.2 | 4.5 | 0.3 | 1.0 | 2.2 | 4.5 | 0.3 | 6 |

| M2.5 | 2.8 | 5.5 | 0.3 | 1.1 | 2.7 | 5.5 | 0.4 | 6 |

| M3 | 3.2 | 6 | 0.4 | 1.3 | 3.2 | 6 | 0.4 | 6 |

| M4 | 4.3 | 8 | 0.5 | 1.6 | 4.3 | 8 | 0.5 | 8 |

| M5 | 5.3 | 10 | 0.5 | 1.8 | 5.3 | 10 | 0.6 | 8 |

| M6 | 6.4 | 11 | 0.5 | 2.2 | 6.4 | 11 | 0.7 | 8 |

| M8 | 8.4 | 15 | 0.5 | 3.4 | 8.4 | 15 | 0.8 | 8 |

| M10 | 10.5 | 18 | 0.8 | 4.0 | – | – | – | – |

The catalogue's entries carry DIN 125 plain-washer dimensions (for example M3: 3.2 / 7 / 0.5), not a curved or

toothed washer's; the presets follow the standards. Not covered: M12 curved (DIN 137 A has no M12); wave washers

(DIN 137 B gives no number of waves).

Preset list: sizes of the step.parts catalogue (MIT), see `library/NOTICE.md`.

# Spring and lock washers (DIN 137 A / DIN 6797 A)

Curved spring washers (DIN 137 form A, M2 to M10) and external tooth lock washers (DIN 6797 form A, M2 to M8).
Presets cover the catalogue's metric curved spring washers and external tooth lock washers.

## Geometry

- **curved** (DIN 137 A): the annulus **d1** × **d2**, **s** thick, curved about an axis parallel to X so that it
  stands **h** (max, the free height) tall: the part of the annulus between two coaxial cylinders of radii R and
  R + s, R chosen so that the inner (upper) surface rises h − s at the rim (R = ((d2/2)² + (h − s)²) / (2 (h − s))).
  Its lowest point is on the XY plane at the origin. The standard gives d1, d2, s and h only; this is the curved form
  those four numbers define.
- **tooth** (DIN 6797 A): envelope, the flat blank, an annulus d1 × d2, s thick, lying on the XY plane. The standard
  gives the number of teeth (6 up to M3, 8 from M4) and the overall height (at least 2 s) but not the teeth's shape,
  width or twist, so the teeth are not modelled.

## Parameters

| Parameter | Meaning |
|---|---|
| `size` | Screw size: M2 to M10 (curved), M2 to M8 (tooth) |
| `style` | `curved` (DIN 137 A) or `tooth` (DIN 6797 A) |
| `material` | `spring-steel` or `stainless` |

## Sources

- **DIN 137** (1985; withdrawn without replacement), *Spring washers, curved or waved*, form A, as reproduced by
  fasten.it (https://fasten.it/en/Norms/Norm/DIN%20137, table "source DIN 137 A"). Cross-check: McMaster-Carr's DIN
  137A washer specifications (https://mcmaster.com/products/washers/specifications-met~din-137a) agree on d1, d2, s
  and h max for M2, M3, M4, M5, M6, M8 and M10.
  Disagreement: the fasten.it page's text calls form A "waved" and form B "curved"; its figure, DIN 137 itself
  (form A gewölbt, form B gewellt) and McMaster have form A curved. The table used here is the one with h max 1.0 (M2)
  to 4.0 (M10), which McMaster sells as DIN 137 A curved washers.
- **DIN 6797:1988-07** (withdrawn), *Toothed lock washers*, form A (external teeth), as reproduced by fasten.it
  (https://fasten.it/en/Norms/Norm/DIN%206797). Cross-checks: Bossard BN 787 "Toothed lock washers type A, external
  teeth" (28 Apr 2017) agrees on every d1, d2, s; Duratool/Farnell datasheet V1.1 (21/07/17,
  https://www.farnell.com/cad/2337766.pdf) agrees on the teeth (M3 6, M4 8). The rows "for hexagon screws only" (M5
  5.1/9, M8 8.2/14) are not used.

| Size | Curved d1 | d2 | s | h max | Tooth d1 | d2 | s | teeth |
|---|---|---|---|---|---|---|---|---|
| M2 | 2.2 | 4.5 | 0.3 | 1.0 | 2.2 | 4.5 | 0.3 | 6 |
| M2.5 | 2.8 | 5.5 | 0.3 | 1.1 | 2.7 | 5.5 | 0.4 | 6 |
| M3 | 3.2 | 6 | 0.4 | 1.3 | 3.2 | 6 | 0.4 | 6 |
| M4 | 4.3 | 8 | 0.5 | 1.6 | 4.3 | 8 | 0.5 | 8 |
| M5 | 5.3 | 10 | 0.5 | 1.8 | 5.3 | 10 | 0.6 | 8 |
| M6 | 6.4 | 11 | 0.5 | 2.2 | 6.4 | 11 | 0.7 | 8 |
| M8 | 8.4 | 15 | 0.5 | 3.4 | 8.4 | 15 | 0.8 | 8 |
| M10 | 10.5 | 18 | 0.8 | 4.0 | – | – | – | – |

The catalogue's entries carry DIN 125 plain-washer dimensions (for example M3: 3.2 / 7 / 0.5), not a curved or
toothed washer's; the presets follow the standards. Not covered: M12 curved (DIN 137 A has no M12); wave washers
(DIN 137 B gives no number of waves).

Preset list: sizes of the step.parts catalogue (MIT), see `library/NOTICE.md`.

Use this part

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Open in STEVE

Open it in STEVE The STEVE runtime runs in STEVE: open the part there, or download the code and bundle.

Get the code

curl -o part.py "https://pythonparts.org/p/steve/spring-lock-washer/v/1.0.0/raw/part.py"

Raw files, bundle and API

part.py
pypart.toml
README.md
bundle.tar.gzthe package, as published

curl "https://pythonparts.org/api/v1/parts/steve/spring-lock-washer/1.0.0"

The version's JSON (parameters, presets, files); add /build?name=value for a build at other values.

About this part

steve58 parts

Profile

Steel (generic)Carbon & alloy steels · Custom finish · 7.9 g/cm³

Mass: 0.15 g

At the parameters shown in the viewer.

License: MIT

Permissive: use, change and sell it; keep the copyright notice.

Runtime: STEVE
Built with: CadQuery 2.9.0.dev0
Published: Nov 1, 2026
Downloads: 1
Builds: 1
Stars: 0
Bundle: 3f7e828aaa8b…

#fastener #washer #spring-washer #curved-washer #tooth-lock-washer #din-137 #din-6797 #metric

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Curved spring washers, DIN 137 form A (M2 to M10): the annulus curved about one axis to its free height h max. External tooth lock washers, DIN 6797 form A (M2 to M8): envelope geometry, the flat blank (the teeth's shape is not given by the standard). Centred on the origin, lying on the XY plane. Dimensions: see the README.

Spring and lock washers (DIN 137 A / DIN 6797 A)

Geometry

curved (DIN 137 A): the annulus d1 × d2, s thick, curved about an axis parallel to X so that it stands h (max, the free height) tall: the part of the annulus between two coaxial cylinders of radii R and R + s, R chosen so that the inner (upper) surface rises h − s at the rim (R = ((d2/2)² + (h − s)²) / (2 (h − s))). Its lowest point is on the XY plane at the origin. The standard gives d1, d2, s and h only; this is the curved form those four numbers define.
tooth (DIN 6797 A): envelope, the flat blank, an annulus d1 × d2, s thick, lying on the XY plane. The standard gives the number of teeth (6 up to M3, 8 from M4) and the overall height (at least 2 s) but not the teeth's shape, width or twist, so the teeth are not modelled.

Parameters

Parameter	Meaning
`size`	Screw size: M2 to M10 (curved), M2 to M8 (tooth)
`style`	`curved` (DIN 137 A) or `tooth` (DIN 6797 A)
`material`	`spring-steel` or `stainless`

Sources

DIN 137 (1985; withdrawn without replacement), Spring washers, curved or waved, form A, as reproduced by fasten.it (https://fasten.it/en/Norms/Norm/DIN%20137, table "source DIN 137 A"). Cross-check: McMaster-Carr's DIN 137A washer specifications (https://mcmaster.com/products/washers/specifications-met~din-137a) agree on d1, d2, s and h max for M2, M3, M4, M5, M6, M8 and M10. Disagreement: the fasten.it page's text calls form A "waved" and form B "curved"; its figure, DIN 137 itself (form A gewölbt, form B gewellt) and McMaster have form A curved. The table used here is the one with h max 1.0 (M2) to 4.0 (M10), which McMaster sells as DIN 137 A curved washers.
DIN 6797:1988-07 (withdrawn), Toothed lock washers, form A (external teeth), as reproduced by fasten.it (https://fasten.it/en/Norms/Norm/DIN%206797). Cross-checks: Bossard BN 787 "Toothed lock washers type A, external teeth" (28 Apr 2017) agrees on every d1, d2, s; Duratool/Farnell datasheet V1.1 (21/07/17, https://www.farnell.com/cad/2337766.pdf) agrees on the teeth (M3 6, M4 8). The rows "for hexagon screws only" (M5 5.1/9, M8 8.2/14) are not used.

Size	Curved d1	d2	s	h max	Tooth d1	d2	s	teeth
M2	2.2	4.5	0.3	1.0	2.2	4.5	0.3	6
M2.5	2.8	5.5	0.3	1.1	2.7	5.5	0.4	6
M3	3.2	6	0.4	1.3	3.2	6	0.4	6
M4	4.3	8	0.5	1.6	4.3	8	0.5	8
M5	5.3	10	0.5	1.8	5.3	10	0.6	8
M6	6.4	11	0.5	2.2	6.4	11	0.7	8
M8	8.4	15	0.5	3.4	8.4	15	0.8	8
M10	10.5	18	0.8	4.0	–	–	–	–

Preset list: sizes of the step.parts catalogue (MIT), see library/NOTICE.md.

1.0.0 Latest Nov 1, 2026 · 1 day ago

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Spring and lock washers (DIN 137 A / DIN 6797 A)

Geometry

Parameters

Sources

Spring and lock washers (DIN 137 A / DIN 6797 A)

Geometry

Parameters

Sources

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