Custom Round-Hook Extension Springs Manufacturer

About Custom Round-Hook Extension Springs

Round-hook extension springs are a practical starting point for return and pull-back functions because the end connection is easy to understand and inspect. The hook geometry still matters: hook diameter, opening, transition into the body and alignment with the pull direction all influence fit and local stress.

Key Design Characteristics

The spring body normally starts under initial tension, so installed load is not determined by rate alone.
Hook opening and bend radius must fit the mating pin or tab without forcing the hook sideways during assembly.
The two hooks should be oriented to match the actual mounting planes.
The end transition is often more highly stressed than the body and deserves its own life review.

What to Specify for a Custom Quote

Wire diameter, body OD and body length
Free length measured between defined hook points
Initial tension and load at one or more extended lengths
Hook inside diameter, opening and relative orientation
Maximum extension, cycles, environment and quantity

Manufacturing Review

For repeatability, the body rate, initial tension and hook position should be controlled separately. A drawing that defines how free length is measured prevents confusion when the hooks are not perfectly circular or lie in different planes.

Common Assembly Roles

Simple latch and lever return
Pull-back between two pins or tabs
Tensioning where a conventional hook connection is acceptable

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.

Model	Wire dia.	OD	ID	Free length	Rate	Material	Coils	Max load
SE-250-0257-0489-0465	2.5 mm	25.7 mm	20.7 mm	48.91 mm	3.854	304 Stainless Steel	7	27.81
SE-040-0038-0099-0481	0.4 mm	3.83 mm	3.03 mm	9.94 mm	0.336	316 Stainless Steel	16.3	1.07
SE-500-0477-2512-0478	5 mm	47.73 mm	37.73 mm	251.22 mm	2.28	65Mn Spring Steel	34.7	118.27
SE-120-0073-0651-0494	1.2 mm	7.32 mm	4.92 mm	65.08 mm	1.853	316 Stainless Steel	42.1	23.6
SE-100-0062-0548-0550	1 mm	6.16 mm	4.16 mm	54.77 mm	1.539	60Si2MnA Spring Steel	46.7	28.21
SE-400-0470-0707-0431	4 mm	46.96 mm	38.96 mm	70.69 mm	4.001	Music Wire (SWP-B)	8	47.07
SE-020-0018-0041-0532	0.2 mm	1.85 mm	1.45 mm	4.06 mm	0.338	Inconel X-750	10.4	0.71
SE-400-0208-1132-0432	4 mm	20.79 mm	12.79 mm	113.15 mm	27.122	316 Stainless Steel	17.2	567.11
SE-020-0024-0107-0553	0.2 mm	2.44 mm	2.04 mm	10.68 mm	0.036	65Mn Spring Steel	39	0.1
SE-015-0014-0099-0582	0.15 mm	1.44 mm	1.14 mm	9.89 mm	0.048	Oil-Tempered Spring Wire (SWO)	48.8	0.21
SE-060-0052-0376-0485	0.6 mm	5.22 mm	4.02 mm	37.61 mm	0.265	Music Wire (SWP-A)	49.2	1.87
SE-200-0194-1213-0526	2 mm	19.37 mm	15.37 mm	121.26 mm	0.624	Music Wire (SWP-A)	48.5	19.13
SE-250-0159-1530-0443	2.5 mm	15.93 mm	10.93 mm	153.04 mm	2.844	304 Stainless Steel	48.9	93.16
SE-100-0057-0335-0548	1 mm	5.74 mm	3.74 mm	33.47 mm	4.067	Inconel X-750	22.8	26.14
SE-050-0069-0132-0512	0.5 mm	6.92 mm	5.92 mm	13.23 mm	0.159	Inconel X-750	14.7	0.66
SE-030-0037-0167-0558	0.3 mm	3.73 mm	3.13 mm	16.72 mm	0.047	Carbon Spring Steel Wire (SWC)	42.3	0.23
SE-100-0067-0308-0516	1 mm	6.74 mm	4.74 mm	30.82 mm	2.869	Inconel X-750	18.2	20.54
SE-250-0189-1072-0456	2.5 mm	18.89 mm	13.89 mm	107.15 mm	1.712	Beryllium Copper (QBe2)	31.1	47.55
SE-200-0134-1165-0514	2 mm	13.39 mm	9.39 mm	116.54 mm	1.297	Phosphor Bronze (QSn4-0.3)	42.8	30.6
SE-120-0070-0345-0500	1.2 mm	6.99 mm	4.59 mm	34.48 mm	5.328	Inconel X-750	19.8	38.3
SE-500-0519-3765-0492	5 mm	51.93 mm	41.93 mm	376.52 mm	0.535	Phosphor Bronze (QSn4-0.3)	57.9	43.27
SE-050-0026-0130-0474	0.5 mm	2.61 mm	1.61 mm	13.02 mm	3.851	301 Stainless Steel	14.9	11.27
SE-200-0241-0707-0539	2 mm	24.06 mm	20.06 mm	70.72 mm	0.549	Oil-Tempered Spring Wire (SWO)	26.8	5.53
SE-400-0483-1628-0499	4 mm	48.3 mm	40.3 mm	162.83 mm	0.96	Oil-Tempered Spring Wire (SWO)	30.3	21.03
SE-020-0027-0069-0497	0.2 mm	2.71 mm	2.31 mm	6.94 mm	0.045	Inconel X-750	22.3	0.19
SE-060-0075-0211-0505	0.6 mm	7.53 mm	6.33 mm	21.14 mm	0.102	Beryllium Copper (QBe2)	22.9	0.57
SE-200-0165-1049-0471	2 mm	16.51 mm	12.51 mm	104.91 mm	0.823	Beryllium Copper (QBe2)	38.2	18.79
SE-300-0344-1378-0586	3 mm	34.35 mm	28.35 mm	137.83 mm	0.77	Inconel X-750	33.7	17.76
SE-500-0576-2810-0468	5 mm	57.63 mm	47.63 mm	280.95 mm	0.906	Music Wire (SWP-B)	46.9	41.58
SE-300-0328-1834-0502	3 mm	32.85 mm	26.85 mm	183.38 mm	0.614	Oil-Tempered Spring Wire (SWO)	49	23.57
SE-400-0395-1513-0527	4 mm	39.49 mm	31.49 mm	151.27 mm	2.192	Oil-Tempered Spring Wire (SWO)	25.8	58.04
SE-200-0179-0289-0583	2 mm	17.92 mm	13.92 mm	28.9 mm	7.019	Music Wire (SWP-B)	5.6	22.71
SE-040-0026-0156-0458	0.4 mm	2.59 mm	1.79 mm	15.6 mm	0.548	Beryllium Copper (QBe2)	26.7	3.3
SE-250-0201-0462-0469	2.5 mm	20.08 mm	15.08 mm	46.22 mm	9.283	Carbon Spring Steel Wire (SWC)	7.6	72.71
SE-060-0070-0274-0537	0.6 mm	7.03 mm	5.83 mm	27.35 mm	0.146	Carbon Spring Steel Wire (SWC)	32.8	0.85
SE-015-0013-0032-0441	0.15 mm	1.27 mm	0.97 mm	3.23 mm	0.272	Carbon Spring Steel Wire (SWC)	13	0.74
SE-180-0095-0394-0520	1.8 mm	9.48 mm	5.88 mm	39.36 mm	15.375	304 Stainless Steel	13	97.79
SE-060-0045-0317-0507	0.6 mm	4.52 mm	3.32 mm	31.66 mm	0.519	Oil-Tempered Spring Wire (SWO)	40.9	3.71
SE-200-0224-0459-0462	2 mm	22.36 mm	18.36 mm	45.88 mm	1.143	316 Stainless Steel	14.3	10.31
SE-060-0052-0360-0561	0.6 mm	5.24 mm	4.04 mm	36 mm	0.249	316 Stainless Steel	45	2.14
SE-400-0334-2719-0590	4 mm	33.39 mm	25.39 mm	271.93 mm	1.824	Music Wire (SWP-A)	54.8	108.34
SE-060-0048-0294-0470	0.6 mm	4.78 mm	3.58 mm	29.43 mm	0.47	60Si2MnA Spring Steel	37.3	3.96
SE-080-0056-0434-0439	0.8 mm	5.61 mm	4.01 mm	43.36 mm	0.844	Carbon Spring Steel Wire (SWC)	42.8	7.54
SE-080-0076-0161-0489	0.8 mm	7.62 mm	6.02 mm	16.12 mm	1.449	60Si2MnA Spring Steel	8.8	5.28
SE-060-0035-0224-0556	0.6 mm	3.51 mm	2.31 mm	22.36 mm	1.851	304 Stainless Steel	24.5	11.57
SE-300-0265-2259-0482	3 mm	26.47 mm	20.47 mm	225.91 mm	0.908	301 Stainless Steel	59.5	46.36
SE-015-0013-0045-0449	0.15 mm	1.26 mm	0.96 mm	4.5 mm	0.2	Carbon Spring Steel Wire (SWC)	18.2	0.65
SE-040-0034-0104-0523	0.4 mm	3.37 mm	2.57 mm	10.42 mm	0.607	65Mn Spring Steel	15.9	1.65
SE-015-0012-0055-0584	0.15 mm	1.24 mm	0.94 mm	5.47 mm	0.144	Inconel X-750	26.8	0.26
SE-015-0022-0045-0551	0.15 mm	2.22 mm	1.92 mm	4.48 mm	0.013	Phosphor Bronze (QSn4-0.3)	21.8	0.03
SE-080-0054-0474-0445	0.8 mm	5.35 mm	3.75 mm	47.45 mm	1.014	Music Wire (SWP-A)	42.5	6.99
SE-030-0034-0207-0580	0.3 mm	3.39 mm	2.79 mm	20.67 mm	0.048	Oil-Tempered Spring Wire (SWO)	56.4	0.27
SE-180-0200-0899-0538	1.8 mm	19.98 mm	16.38 mm	89.88 mm	0.433	Oil-Tempered Spring Wire (SWO)	39.8	8.02

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.

Configuration	Data type	Key parameters	Material / basis
Engineering Data 01	Engineering Data	Reference parameter: Semi-Circular / Round-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

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

Music wire is common for economical high-strength extension springs in dry service. Stainless steel is often selected for moisture, washdown or cleaner environments. The hook bend can be the limiting feature, so material ductility matters as well as strength.

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

Engineering Support

Spring Engineering Guides

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

Material data Inconel X-750 Extension Springs Engineering Data 8 matching round-hook extension springs data rows are included in the category. Material data Oil-Tempered Spring Wire (SWO) Extension Springs Engineering Data 8 matching round-hook extension springs data rows are included in the category. Material data Carbon Spring Steel Wire (SWC) Extension Springs Engineering Data 6 matching round-hook extension springs data rows are included in the category. Wire diameter 0.15 mm Extension Springs Engineering Data 5 matching round-hook extension springs data rows are included in the category. Wire diameter 0.6 mm Extension Springs Engineering Data 7 matching round-hook extension springs data rows are included in the category. Wire diameter 1.8 mm Extension Springs Engineering Data 2 matching round-hook extension springs data rows are included in the category.

Compare Designs

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

Product Questions

Round-Hook Extension Springs FAQ

What is initial tension in an extension spring?

It is the force already present in the closed-coil body before the spring begins to extend. It affects the first part of the load curve and should be specified when the starting force matters.

Should the hook be sized tightly around the mating pin?

Usually some clearance is needed for assembly and movement. A hook that binds on the pin can create bending and wear that were not part of the intended axial loading.

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

Spring Type Wire / Thickness (mm) Outside Diameter / Envelope (mm) Inside Diameter / Bore (mm) Free Length / Height (mm) Spring Rate / Torque Load / Torque Coils / Turns / Leaves Quantity * Material Finish Drawing PDF, CAD, image or ZIP; maximum 10 MB.

Contact Information

Company Contact Name * Email * Phone / WhatsApp Country / Region Application

Notes