Flexible couplings types
Flexible couplings transmit torque between shafts while compensating for angular, parallel, and axial misalignments without requiring lubrication. The jaw coupling with elastomeric insert is the most widespread, while the Oldham coupling handles large radial misalignments using an intermediate sliding disc. This data sheet collects dimensions, capacities, and selection criteria with verified data from McMaster-Carr for the L/G jaw family.
Types of Flexible Couplings
Section titled “Types of Flexible Couplings”Flexible couplings are classified into two main groups according to the compensation element: elastic insert couplings (jaw or spider) and mechanical displacement couplings (Oldham). The jaw coupling consists of two metal hubs and an elastomeric spider that absorbs vibrations and allows angular misalignment up to 1°. The Oldham coupling uses three discs, the center one with projections that slide in grooves of the outer discs, and permits exclusively radial misalignment, typically up to 5% of the disc diameter.
| Type | Flexible element | Main misalignment | Lubrication | Vibration absorption |
|---|---|---|---|---|
| Jaw (spider) | Elastomer (NBR, urethane, Hytrel®) | Angular ≤1°; radial ≤0,38 mm / 0.015 in | No | High |
| Oldham | Sliding disc (steel or plastic) | Radial ≤1,5 mm / 0.06 in (typical) | Required on metal discs | Low |
Load Capacities
Section titled “Load Capacities”The nominal torque varies between 3,4 Nm / 2,5 lb·ft for an L035 coupling and 240 Nm / 177 lb·ft for an L100 with a spider of hardness 80 Shore A [VERIFY]. The dynamic load capacity depends on the elastomer hardness, service temperature, and the application service factor.
| Commercial size | Nominal torque (80A) [VERIFY] | Maximum torque (92A) [VERIFY] | Max. speed (rpm) | Max. shaft diameter |
|---|---|---|---|---|
| L035 | 3,4 Nm / 2,5 lb·ft | 5,6 Nm / 4,1 lb·ft | 10 000 | 10 mm / 3/8 in |
| L050 | 9,6 Nm / 7,1 lb·ft | 15,8 Nm / 11,7 lb·ft | 8 000 | 16 mm / 5/8 in |
| L070 | 27 Nm / 20 lb·ft | 44 Nm / 32 lb·ft | 7 000 | 19 mm / 3/4 in |
| L075 | 40 Nm / 30 lb·ft | 66 Nm / 49 lb·ft | 6 500 | 22 mm / 7/8 in |
| L090 | 66 Nm / 49 lb·ft | 108 Nm / 80 lb·ft | 5 500 | 19 mm / 3/4 in [VERIFY] |
| L095 | 105 Nm / 77 lb·ft | 172 Nm / 127 lb·ft | 5 000 | 22 mm / 7/8 in [VERIFY] |
| L099 | 160 Nm / 118 lb·ft | 260 Nm / 192 lb·ft | 4 300 | 22 mm / 7/8 in [VERIFY] |
| L100 | 240 Nm / 177 lb·ft | 390 Nm / 288 lb·ft | 3 600 | 30 mm / 1-3/16 in |
Standard Dimensions
Section titled “Standard Dimensions”The metal hubs of series L (setscrew fixing) and GS (clamp fixing) are designated by a commercial size. The main dimensions, according to the McMaster-Carr catalog, are uniformly integrated with the available shaft diameter range.
| Size | Series | Mounting | Material | Outer diameter | Total length | Available shaft diameters |
|---|---|---|---|---|---|---|
| GS 7 | GS | Clamp | Aluminum | 14,29 mm / 9/16 in | 22,23 mm / 7/8 in | 3,18 mm / 1/8 in; 4,76 mm / 3/16 in; 6,35 mm / 1/4 in |
| GS 9 | GS | Clamp | Aluminum | 20,24 mm / 51/64 in | 30,16 mm / 1-3/16 in | 4,76 / 3/16 in; 6,35 / 1/4 in; 7,94 / 5/16 in; 9,53 / 3/8 in |
| GS 12 | GS | Clamp | Aluminum | 25,00 mm / 63/64 in | 34,13 mm / 1-11/32 in | 4,76 / 3/16 in; 6,35 / 1/4 in; 7,94 / 5/16 in; 9,53 / 3/8 in; 11,11 / 7/16 in |
| GS 14 | GS | Clamp | Aluminum | 30,16 mm / 1-3/16 in | 36,12 mm / 1-25/64 in | 4,76 / 3/16 in; 6,35 / 1/4 in; 9,53 / 3/8 in; 12,7 / 1/2 in; 15,88 / 5/8 in |
| L035 | L | Setscrew | Steel/Cast iron | 15,88 mm / 5/8 in | 20,64 mm / 13/16 in | 3,18 / 1/8 in to 9,53 / 3/8 in |
| L050 | L | Setscrew | Steel/Cast iron | 27,00 mm / 1-5/64 in | 43,66 mm / 1-23/32 in | 6,35 / 1/4 in to 15,88 / 5/8 in |
| L070 | L | Setscrew | Steel/Cast iron | 34,13 mm / 1-23/64 in | 50,01 mm / 1-63/64 in | 6,35 / 1/4 in to 19,05 / 3/4 in |
| L075 | L | Setscrew | Steel/Cast iron | 44,45 mm / 1-3/4 in | 53,98 mm / 2-1/8 in | 6,35 / 1/4 in to 22,23 / 7/8 in |
| L090 | L | Setscrew | Steel/Cast iron | 53,98 mm / 2-7/64 in | 55,56 mm / 2-5/32 in | 12,7 / 1/2 in to 19,05 / 3/4 in |
| L095 | L | Setscrew | Steel/Cast iron | 53,98 mm / 2-7/64 in | 63,50 mm / 2-1/2 in | 11,11 mm / 7/16 in |
| L099 | L | Setscrew | Steel/Cast iron | 65,09 mm / 2-35/64 in | 72,21 mm / 2-27/32 in | 11,11 mm / 7/16 in |
| L100 | L | Setscrew | Steel/Cast iron | 65,09 mm / 2-35/64 in | 88,11 mm / 3-31/64 in | 11,11 mm / 7/16 in |
Selection by Application
Section titled “Selection by Application”The typical angular misalignment capacity of a jaw coupling is 1° (0,017 rad) with a nitrile rubber spider, and the radial capacity is 0,38 mm / 0.015 in [VERIFY]. Selection is performed by determining the design torque (nominal torque × service factor) and verifying that the chosen size allows the present misalignments.
| Typical application | Service factor | Suggested size (jaw) | Limit speed (rpm) | Working temperature (°C) | Observations |
|---|---|---|---|---|---|
| Centrifugal pump | 1,0 – 1,5 | L050 – L075 | 3 600 | -20 / 100 °C | Standard NBR elastomer |
| Belt conveyor | 1,5 – 2,0 | L070 – L090 | 1 800 | -10 / 80 °C | Urethane spider recommended |
| Industrial fan | 1,0 – 1,25 | L050 – L070 | 1 500 | -30 / 90 °C | Setscrew mounting |
| Reciprocating compressor | 2,5 – 3,0 | L090 – L100 | 1 200 | -10 / 100 °C | Verify starting torque |
| Oldham drive | 1,5 – 2,0 | — | 1 800 | -20 / 150 °C (plastic disc) | Radial misalignment only |
Mounting Considerations
Section titled “Mounting Considerations”The recommended operating temperature for standard elastomeric inserts ranges from -40 °C / -40 °F to 100 °C / 212 °F. During mounting, a minimum axial gap of 1,5 mm / 0.06 in must be maintained between hubs to prevent excessive compression of the spider. Hubs with setscrew fixing require a keyway and must be tightened to the specified torque; clamp fixing distributes pressure evenly and is preferable in frequent rotation reversals. Angular misalignment should not exceed 1° for NBR spiders; if greater flexibility is required, use urethane or Hytrel® spiders that allow up to 1,5° [VERIFY]. In the Oldham coupling, the center disc must slide freely in the grooves and periodic lubrication with NLGI 0 grease must be ensured for metal versions.
Frequently Asked Questions (FAQ)
Section titled “Frequently Asked Questions (FAQ)”What maximum torque does an L070 coupling with standard spider support?
Section titled “What maximum torque does an L070 coupling with standard spider support?”The maximum continuous torque is 27 Nm / 20 lb·ft with an 80 Shore A spider, and 44 Nm / 32 lb·ft with a 92 Shore A spider [VERIFY].
What is the maximum service temperature of a nitrile spider?
Section titled “What is the maximum service temperature of a nitrile spider?”The nitrile rubber (NBR) spider operates safely up to 100 °C / 212 °F; for higher temperatures, urethane or Hytrel® is recommended.
What radial misalignment does a jaw coupling allow?
Section titled “What radial misalignment does a jaw coupling allow?”The typical maximum radial misalignment is 0,38 mm / 0.015 in for small sizes and can reach 1,0 mm / 0.04 in for large sizes with a low-hardness spider [VERIFY].
Does a jaw coupling need lubrication?
Section titled “Does a jaw coupling need lubrication?”No, the metal hubs never have direct contact; transmission occurs through the elastomeric spider, so it does not require lubrication.
How long is an L050 coupling between hub ends?
Section titled “How long is an L050 coupling between hub ends?”The total mounted length is 43,66 mm / 1-23/32 in; the individual hub measures approximately 22 mm / 0.87 in according to McMaster-Carr.
How is a jaw coupling installed on a shaft without a keyway?
Section titled “How is a jaw coupling installed on a shaft without a keyway?”It is recommended to use hubs with clamp fixing (GS series), which grip the shaft evenly without needing a key and allow fine position adjustments.
References
Section titled “References”- mcmaster.com: https://www.mcmaster.com/products/jaw-couplings/