Skip to content
Contact Request a Quote

Extension Springs

Custom German-Hook Extension Springs

An extension spring with a compact German-style hook profile used when the connection geometry needs more control than a simple round loop provides.

Request a Quote See application guidance
German-Hook Extension Springs manufactured by CustomSprings
Typical configurations
47
Wire diameter
0.15–5 mm
Outside diameter
1.2–46.41 mm
Free length
2.82–266.18 mm

About Custom German-Hook Extension Springs

German-hook extension springs are chosen mainly for the way the end connects to the assembly. The body behaves like a conventional extension spring, while the hook profile can fit a specific pin, slot or nearby obstruction. The end should therefore be dimensioned from the mating hardware, not selected only by appearance.

Key Design Characteristics

  • Hook height, opening and bend position define how the spring sits on the anchor.
  • The hook plane should match the pull direction so the end is not twisted under load.
  • Initial tension remains an important body parameter even when the end geometry is custom.
  • Local bend stress at the hook transition can control fatigue life before the coil body does.

What to Specify for a Custom Quote

  • Body wire diameter, OD and coil length
  • Free length using a clearly defined end-to-end measurement
  • Initial tension and required loads through the working extension
  • Pin or tab dimensions and full German-hook geometry
  • Hook orientation, maximum travel, cycles, material and finish

Manufacturing Review

Inspection should separate body dimensions from end-form dimensions. For replacement parts, a clear side view and end view of the hook is more useful than an overall-length measurement alone.

Common Assembly Roles

  • Compact pull-back linkages
  • OEM replacement springs with fixed anchor geometry
  • Latch and control mechanisms where hook shape is constrained

Product Data

Typical Spring Configurations

Use these data points to compare practical starting dimensions and material options. Final production specifications are confirmed against your drawing and working conditions.

ModelWire dia.ODIDFree lengthRateMaterialCoilsMax load
SE-300-0198-1363-0570 3 mm 19.8 mm 13.8 mm 136.33 mm 5.623 Oil-Tempered Spring Wire (SWO) 30 127.14
SE-150-0113-0594-0421 1.5 mm 11.34 mm 8.34 mm 59.39 mm 1.848 60Si2MnA Spring Steel 28.4 26.66
SE-050-0064-0162-0442 0.5 mm 6.39 mm 5.39 mm 16.19 mm 0.087 Beryllium Copper (QBe2) 21.2 0.36
SE-250-0211-0648-0572 2.5 mm 21.07 mm 16.07 mm 64.79 mm 3.654 316 Stainless Steel 14.4 49.1
SE-040-0030-0208-0571 0.4 mm 2.95 mm 2.15 mm 20.77 mm 0.382 60Si2MnA Spring Steel 39.9 2.46
SE-400-0295-0591-0508 4 mm 29.52 mm 21.52 mm 59.13 mm 24.143 Oil-Tempered Spring Wire (SWO) 6.3 237.03
SE-500-0279-1857-0528 5 mm 27.87 mm 17.87 mm 185.67 mm 21.409 Oil-Tempered Spring Wire (SWO) 24.1 925.68
SE-200-0221-0550-0501 2 mm 22.09 mm 18.09 mm 55.04 mm 1.313 Music Wire (SWP-A) 14.9 15.98
SE-030-0032-0180-0529 0.3 mm 3.15 mm 2.55 mm 17.96 mm 0.042 Beryllium Copper (QBe2) 50.1 0.22
SE-250-0290-0392-0557 2.5 mm 29.03 mm 24.03 mm 39.17 mm 1.902 Beryllium Copper (QBe2) 6.6 10.45
SE-030-0038-0213-0486 0.3 mm 3.75 mm 3.15 mm 21.29 mm 0.03 301 Stainless Steel 56.2 0.21
SE-015-0012-0028-0524 0.15 mm 1.21 mm 0.91 mm 2.82 mm 0.363 Music Wire (SWP-B) 11.6 0.91
SE-300-0278-1335-0438 3 mm 27.79 mm 21.79 mm 133.48 mm 1.581 Oil-Tempered Spring Wire (SWO) 33.2 47.56
SE-180-0139-0994-0559 1.8 mm 13.87 mm 10.27 mm 99.4 mm 1.441 Inconel X-750 40.9 27.51
SE-080-0057-0259-0568 0.8 mm 5.66 mm 4.06 mm 25.93 mm 1.412 304 Stainless Steel 21.8 6.68
SE-050-0052-0282-0581 0.5 mm 5.2 mm 4.2 mm 28.16 mm 0.068 Phosphor Bronze (QSn4-0.3) 45.1 0.6
SE-100-0120-0509-0467 1 mm 11.99 mm 9.99 mm 50.91 mm 0.192 Music Wire (SWP-A) 38.8 2.35
SE-040-0027-0205-0510 0.4 mm 2.67 mm 1.87 mm 20.46 mm 0.46 301 Stainless Steel 41 2.66
SE-100-0113-0716-0544 1 mm 11.26 mm 9.26 mm 71.56 mm 0.162 Carbon Spring Steel Wire (SWC) 56.1 1.78
SE-060-0066-0377-0588 0.6 mm 6.55 mm 5.35 mm 37.67 mm 0.131 Oil-Tempered Spring Wire (SWO) 46.3 0.83
SE-150-0128-0510-0447 1.5 mm 12.75 mm 9.75 mm 50.96 mm 1.422 Oil-Tempered Spring Wire (SWO) 24.7 10.26
SE-400-0367-2126-0460 4 mm 36.74 mm 28.74 mm 212.59 mm 1.502 304 Stainless Steel 41.9 57.41
SE-050-0049-0255-0531 0.5 mm 4.94 mm 3.94 mm 25.53 mm 0.175 60Si2MnA Spring Steel 40.2 1.31
SE-050-0047-0312-0425 0.5 mm 4.66 mm 3.66 mm 31.25 mm 0.083 Phosphor Bronze (QSn4-0.3) 53.8 0.74
SE-250-0191-0435-0430 2.5 mm 19.08 mm 14.08 mm 43.52 mm 16.927 60Si2MnA Spring Steel 5 107.74
SE-150-0073-0704-0535 1.5 mm 7.26 mm 4.26 mm 70.36 mm 7.786 60Si2MnA Spring Steel 33.6 117.86
SE-500-0464-2662-0552 5 mm 46.41 mm 36.41 mm 266.18 mm 1.999 Carbon Spring Steel Wire (SWC) 43.2 72.36
SE-400-0402-1462-0504 4 mm 40.22 mm 32.22 mm 146.23 mm 1.303 Beryllium Copper (QBe2) 24.8 26.38
SE-500-0306-1651-0483 5 mm 30.61 mm 20.61 mm 165.1 mm 15.374 Oil-Tempered Spring Wire (SWO) 23.9 372.63
SE-300-0235-0473-0575 3 mm 23.51 mm 17.51 mm 47.3 mm 10.431 Beryllium Copper (QBe2) 5.4 56.02
SE-500-0392-1324-0564 5 mm 39.2 mm 29.2 mm 132.36 mm 7.745 301 Stainless Steel 17.4 182.77
SE-250-0212-0527-0547 2.5 mm 21.2 mm 16.2 mm 52.68 mm 4.854 Music Wire (SWP-A) 12.2 48.19
SE-250-0268-1545-0521 2.5 mm 26.75 mm 21.75 mm 154.49 mm 0.575 Music Wire (SWP-B) 47.2 25.62
SE-050-0053-0133-0562 0.5 mm 5.28 mm 4.28 mm 13.32 mm 0.372 Inconel X-750 15.2 1.47
SE-060-0035-0159-0428 0.6 mm 3.5 mm 2.3 mm 15.86 mm 2.518 304 Stainless Steel 18.2 10.9
SE-015-0013-0105-0540 0.15 mm 1.29 mm 0.99 mm 10.48 mm 0.065 65Mn Spring Steel 52.1 0.33
SE-300-0369-1752-0437 3 mm 36.88 mm 30.88 mm 175.24 mm 0.383 304 Stainless Steel 46.9 18.18
SE-120-0074-0825-0476 1.2 mm 7.44 mm 5.04 mm 82.54 mm 1.513 Inconel X-750 55.7 20.82
SE-500-0379-2502-0487 5 mm 37.86 mm 27.86 mm 250.16 mm 2.572 Beryllium Copper (QBe2) 41.1 143.9
SE-250-0153-0457-0498 2.5 mm 15.31 mm 10.31 mm 45.69 mm 20.035 301 Stainless Steel 8 128.32
SE-020-0012-0111-0444 0.2 mm 1.2 mm 0.8 mm 11.11 mm 0.21 Phosphor Bronze (QSn4-0.3) 39.1 0.92
SE-100-0057-0671-0461 1 mm 5.73 mm 3.73 mm 67.11 mm 1.495 316 Stainless Steel 54.5 27.96
SE-030-0026-0128-0475 0.3 mm 2.63 mm 2.03 mm 12.85 mm 0.106 Phosphor Bronze (QSn4-0.3) 30.9 0.49
SE-050-0045-0378-0457 0.5 mm 4.52 mm 3.52 mm 37.77 mm 0.164 Oil-Tempered Spring Wire (SWO) 58.1 1.78
SE-300-0166-0713-0517 3 mm 16.61 mm 10.61 mm 71.34 mm 25.383 60Si2MnA Spring Steel 12.5 312.83
SE-060-0080-0416-0495 0.6 mm 7.97 mm 6.77 mm 41.55 mm 0.03 Phosphor Bronze (QSn4-0.3) 55 0.25
SE-200-0160-0375-0513 2 mm 16.05 mm 12.05 mm 37.49 mm 5.026 304 Stainless Steel 9.9 21.29

Rate: N/mm; maximum load: N. Dimensions are in millimeters.

Engineering Data

Typical Dimensions & Design Data

Use these data points to compare geometry, material and working parameters when defining your custom spring. Final values are reviewed and confirmed for the actual assembly before production.

ConfigurationData typeKey parametersMaterial / basis
Engineering Data 01 Engineering Data
  • Reference parameter: German-Hook Extension Spring
  • Data use: Engineering reference
 Per drawing / published type
Engineering Data 02 Manufacturing Range
  • Reference parameter: 0.0508 mm
  • Reference parameter: 15.875 mm
  • Status: Custom made
 Common spring steels, stainless steels and alloys
Engineering Data 03 Design Input
  • Key field 1: Wire diameter
  • Key field 2: Body OD
  • Key field 3: Free length / initial tension
 Per drawing
Typical Configuration 04Data point Typical Configuration
  • Wire diameter: 2.2 mm
  • Outside diameter: 15 mm
  • Free length: 74.2 mm
  • Spring rate: 4.4626 N/mm
  • Maximum Length: 123.8446 mm
  • Maximum force: 255.41078 N
 Music wire
Typical Configuration 05Data point Typical Configuration
  • Wire diameter: 1.9 mm
  • Outside diameter: 16 mm
  • Free length: 102 mm
  • Spring rate: 1.11439 N/mm
  • Maximum Length: 230.296 mm
  • Maximum force: 161.0078 N
 Music wire
Typical Configuration 06Data point Typical Configuration
  • Wire diameter: 1.5 mm
  • Outside diameter: 9.2 mm
  • Free length: 70 mm
  • Spring rate: 2.85998 N/mm
  • Maximum Length: 111.8376 mm
  • Maximum force: 139.66881 N
 Music wire

Design note: dimensions, force / torque, material, tolerances, fatigue life and compliance are finalized against your drawing and operating conditions during quotation.

Next Design Decisions

Next Steps for Your Spring Design

Once the spring style is selected, confirm how it works in the assembly, which material suits the environment, how it will be manufactured and which dimensions and performance points should be controlled on the drawing.

Applications

Where this spring style fits

Review best-fit uses, assembly constraints and situations where another spring style may be a better choice.

View application guidance →

Materials

Choose the material for the environment

Material selection follows the same strength and corrosion needs as other extension springs, but very tight hook bends may narrow the practical choices for hard or low-ductility wire conditions.

Compare spring materials →

Manufacturing

Plan prototype and production

Review forming, heat treatment, secondary operations, inspection and the path from first samples to repeat production.

View manufacturing capabilities →

Engineering Data

Open matching engineering guides

Matching material and wire-diameter pages provide additional design data for material and size selection.

Open Spring Engineering Guide →

Material Direction

Common Material Families to Review

The links below are selection guides, not a claim that every grade is suitable for every size or load.

Carbon & Alloy Spring SteelsSelection guide Copper Alloy Spring MaterialsSelection guide Stainless Steel Spring MaterialsSelection guide Nickel & High-Temperature Spring AlloysSelection guide

Related Spring Design Guides

Review the design and measurement requirements for this spring family.

Engineering Support

Spring Engineering Guides

Use these guides to compare material, wire diameter and standard requirements before finalizing the product drawing.

Material data Oil-Tempered Spring Wire (SWO) Extension Springs Engineering Data 8 matching german-hook extension springs data rows are included in the category. Material data 60Si2MnA Spring Steel Extension Springs Engineering Data 6 matching german-hook extension springs data rows are included in the category. Material data Beryllium Copper (QBe2) Extension Springs Engineering Data 6 matching german-hook extension springs data rows are included in the category. Wire diameter 0.15 mm Extension Springs Engineering Data 2 matching german-hook extension springs data rows are included in the category. Wire diameter 0.6 mm Extension Springs Engineering Data 3 matching german-hook extension springs data rows are included in the category. Wire diameter 1.8 mm Extension Springs Engineering Data 1 matching german-hook extension springs data row are included in the category.

Compare Designs

Use these alternatives when the available space, connection style, travel or force direction changes.

Round-Hook Extension Springs manufactured by CustomSprings

Extension Springs

Round-Hook Extension Springs

An extension spring with simple round hooks for straightforward pin, hole or tab connections where the pull direction stays close to the spring axis.

English-Hook Extension Springs manufactured by CustomSprings

Extension Springs

English-Hook Extension Springs

A compact end-hook extension spring suited to small linkages and constrained connections where the attachment needs to stay close to the coil body.

Offset-Hook Extension Springs manufactured by CustomSprings

Extension Springs

Offset-Hook Extension Springs

An extension spring with an intentionally offset connection point for assemblies where the anchors do not line up with the coil centerline.

Product Questions

German-Hook Extension Springs FAQ

Why choose a German hook instead of a round hook?

The main reason is fit. It can place the contact point differently or fit a more constrained anchor, while the spring body can remain similar.

Can the hook geometry be changed without changing the spring body?

Often yes, but changing the end can alter overall length, local stress and installed alignment, so the full assembly should still be checked.

RFQ

Send the Working Requirement

A drawing is ideal. If you do not have one yet, provide the dimensions, load or torque, travel, environment and expected quantity that matter in the assembly.

CustomSprings Engineering Catalog

Request This Spring

Send your dimensions, quantity and drawing for engineering review.

Request a Custom Quote

Fields marked * are required. A drawing is recommended for accurate review.

Spring Requirements
Contact Information