# Spring pins

Slotted and coiled spring-pin retention, duty classes, supplier dimensions, and the limits of shear-test ratings.

Reviewed: 2026-10-30

Tags: components, fasteners, pins

SPIROL lists minimum double-shear strength for its nominal **3 mm** standard-duty coiled pin as **5.50 kN** for the carbon/alloy/chrome-stainless group and **4.20 kN** for nickel stainless. The cited test uses nominal-size holes in members of at least **700 HV**, with no more than **0.15 mm** clearance between support and loading members. Use installed joint evidence for the actual host and load path. [SPIROL coiled guide, PDF page 19, printed 17](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=19), [SPIROL coiled guide, PDF page 8, printed 6](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=8).

Spring pins compress radially in the hole. Slotted designs narrow an open gap, while coiled designs flex their wrapped section. [SPIROL coiled guide, PDF page 3, printed 1](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=3), [SPIROL slotted guide, PDF page 2](https://www.spirol.com/assets/files/sltp-slotted-spring-pin-design-guide-uk.pdf#page=2).

## Construction and retention

The free pin exceeds the intended hole diameter. Installation reduces it elastically. [SPIROL coiled guide, PDF page 4, printed 2](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=4).

Solid pins belong to a separate construction category. SPIROL contrasts spring-pin compression with interference-retained solid pins that displace the host material, including knurled solid pins whose knurls engage the hole wall. This comparison concerns those retention arrangements; it does not assign every solid dowel, taper pin, or clearance-fit locating pin the same retention mechanism. A pin's locating function alone does not identify it as a spring pin. [SPIROL coiled guide, PDF page 4, printed 2](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=4)

SPIROL also distinguishes its own **Standard Slotted** family from its **ISO 8752** slotted offering. Its Standard Slotted construction has a slot narrower than the wall thickness. The named supplier family matters alongside the general word “slotted”; the two catalogue tables have different free diameters and wall dimensions. [SPIROL slotted guide, PDF pages 2, 5 and 6](https://www.spirol.com/assets/files/sltp-slotted-spring-pin-design-guide-uk.pdf#page=2)

## Coiled duty classes and host material

SPIROL offers light, standard, and heavy coiled duties as different combinations of flexibility and strength at a nominal diameter. “Heavy” is not a general quality grade. The guide relates duty to the host material, applied loading, and available diameter: an overly stiff pin can damage a hole, while an overly flexible pin can fatigue prematurely. [SPIROL coiled guide, PDF page 3, printed 1](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=3)

The supplier associates standard duty with nonferrous and mild-steel components, while also discussing its use in hardened components for shock absorption. It associates heavy duty with hardened materials where space prevents a larger standard-duty pin, and light duty with soft, brittle, or thin hosts and holes near edges. These are SPIROL's application categories, not a universal host-hardness threshold or a completed joint design. [SPIROL coiled guide, PDF page 9, printed 7](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=9)

## Exact nominal 3 mm catalogue examples

The table compares selected **SPIROL metric nominal 3 mm** entries. Dimensions are in millimetres. D is the free pin-body diameter, not the installed hole diameter. The coiled tables expressly state that dimensions apply before plating; the Standard Slotted table carries the same condition. The ISO 8752 entry is SPIROL's supplier table, rather than a transcription of the full ISO standard. [Coiled standard duty, PDF page 19](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=19), [coiled heavy duty, PDF page 20](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=20), [coiled light duty, PDF page 21](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=21), [slotted tables, PDF pages 5–6](https://www.spirol.com/assets/files/sltp-slotted-spring-pin-design-guide-uk.pdf#page=5)

| SPIROL family / duty | Free diameter D, min–max | Recommended hole, min–max | Additional dimension in that table |
| --- | --- | --- | --- |
| Coiled, light duty | 3.15–3.35 | 3.00–3.10 | Chamfer diameter B: 2.90 max; length C: 0.90 REF |
| Coiled, standard duty | 3.15–3.30 | 3.00–3.10 | Chamfer diameter B: 2.90 max; length C: 0.90 REF |
| Coiled, heavy duty | 3.12–3.25 | 3.00–3.10 | Chamfer diameter B: 2.90 max; length C: 0.90 REF |
| Standard Slotted, metric | 3.14–3.25 | 3.00–3.10 | Nominal wall S: 0.65; chamfer length C: 0.20–1.00 |
| ISO 8752 Slotted, metric | 3.30–3.50 | 3.00–3.10 | Nominal wall S: 0.60; chamfer length C: 0.50–0.70 |

This comparison shows that a common nominal size and recommended hole range can coexist with different free diameters, wall dimensions, and chamfer definitions. A reference chamfer length is also different from a minimum–maximum tolerance. The table does not establish interchangeability, insertion force, retention force, or equivalence at a particular stock length. [SPIROL coiled guide, PDF pages 19–21](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=19), [SPIROL slotted guide, PDF pages 5–6](https://www.spirol.com/assets/files/sltp-slotted-spring-pin-design-guide-uk.pdf#page=5)

## Material condition is family-specific

SPIROL's high-carbon material tables identify UNS G10700 / G10740, also listed as C67S / C75S, but specify different Vickers hardness ranges: **HV 420–545** for its coiled family, **HV 458–560** for Standard Slotted, and **HV 420–520** in the slotted guide's ISO 8752 column. Both guides describe their high-carbon spring pins as heat treated. The shared grade names do not erase these family-specific condition ranges. [SPIROL coiled guide, PDF page 13, printed 11](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=13), [SPIROL slotted guide, PDF page 8, printed 6](https://www.spirol.com/assets/files/sltp-slotted-spring-pin-design-guide-uk.pdf#page=8)

The same guides distinguish work-hardened austenitic stainless pins from hardened martensitic stainless pins. SPIROL specifically cautions against austenitic stainless coiled or slotted pins in hardened holes and against their use for high shock and vibration. Thus “stainless” alone does not specify heat-treatment condition or host compatibility. These statements are supplier-specific material guidance, not a corrosion or service-life qualification for an unspecified environment. [SPIROL coiled guide, PDF page 13](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=13), [SPIROL slotted guide, PDF page 8](https://www.spirol.com/assets/files/sltp-slotted-spring-pin-design-guide-uk.pdf#page=8)

## What the shear ratings measure

For its nominal 3 mm **standard-duty coiled** entry, SPIROL lists minimum double-shear strengths of **5.50 kN** for the carbon/alloy/chrome-stainless grouping and **4.20 kN** for nickel stainless. These are the table's material-group ratings, not allowable forces for an arbitrary assembly. The page identifies ASME B18.8.3M and ISO 8749 as the shear-test procedures. [SPIROL coiled guide, PDF page 19, printed 17](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=19)

SPIROL's accompanying ISO 8749 test description uses support and loading members with nominal-size holes and hardness of at least **700 HV**, a support-to-load-member clearance no greater than **0.15 mm**, shear planes at least one pin diameter from each end and at least two diameters apart, and a test speed no greater than **13 mm/min**. For pins too short for double shear, the description instead uses two pins tested simultaneously in single shear. The reported double-shear strength is the maximum load at or before fracture. These are conditions in the manufacturer's test description, not recommended production-hole or assembly dimensions. The full ISO standard and its edition were not independently inspected here. [SPIROL coiled guide, PDF page 8, printed 6](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=8)

The slotted guide explicitly identifies host hardness, loading rate, shear-plane spacing, and end distances as reasons application results differ from catalogue shear tests. It also describes slot orientation as affecting measured shear behaviour. Accordingly, a catalogue fracture rating does not by itself establish fatigue endurance, host-hole bearing capacity, axial retention, or an assembly's usable load. Catalogue fracture ratings likewise do not establish insertion force, reuse suitability, or the performance of a nested-pin assembly. [SPIROL slotted guide, PDF page 10, printed 8](https://www.spirol.com/assets/files/sltp-slotted-spring-pin-design-guide-uk.pdf#page=10), [SPIROL coiled guide, PDF pages 8–9](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=8)

## Source versions and coverage

Both cited SPIROL guides carry **© 2026** and a **05/26** issue marking on their final pages. They were accessed on **October 30, 2026 (PDT)**. The coiled guide is the US file and the slotted guide the UK file; the selected examples above use their metric tables. The dated guide issue, retrieval date, and the unspecified editions of standards named within the guides are separate identifiers. [Coiled guide, PDF page 24](https://www.spirol.com/assets/files/cldp-coiled-spring-pins-design-guide-us.pdf#page=24), [slotted guide, PDF page 16](https://www.spirol.com/assets/files/sltp-slotted-spring-pin-design-guide-uk.pdf#page=16)

These sources establish manufacturer construction descriptions, catalogue dimensions, material conditions, and stated test contexts. They do not establish a current controlled drawing for an individual supplied part, lot certification, universal spring-pin interchangeability, or customer-specific assembly qualification.

## Related reference

[Hardware and component references](../index.md) covers the broader assembly-process context.