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Shaft Coupling Attributes & Specifications

A shaft coupling connects two rotating shafts and transmits torque, usually while absorbing some misalignment. The category runs from rigid sleeve and flange couplings through elastomeric jaw and tire types, gear, grid, disc, and diaphragm couplings, to the Oldham, bellows, and beam couplings used in servo work. Buyers are MRO planners replacing a failed spider, design engineers specifying to a service factor, and pump and gearbox rebuilders matching an existing frame.

The data is hard for three structural reasons. The SKU is often not the product: an "L095 coupling" may be a single hub, a spider, a spider cover, or a complete assembly, and manufacturers sell all four under near-identical descriptions. One size code then explodes into hundreds of bore and keyway variants across inch and metric, which suppliers spell four different ways. And the numbers buyers actually select on — misalignment limits, element temperature range, unbalance class — live in a rating table inside a handbook PDF, not in the line-item file the supplier sends.

Core

Every SKU needs these. Without them the record is not a product, it is a row.

Coupling Type
enum
Jaw (elastomeric insert)

First cut on every filter rail. Jaw, gear, grid, disc, and rigid solve different misalignment and shock problems and are not substitutes.

Coupling Size / Series Designation
identifier
L095

The size code governs which hubs, spiders, and covers interchange. Buyers search it directly and it is how the aftermarket is ordered.

Bore Dia. 1
number · in or mm
0.625 in (5/8 in)

The driving-side shaft diameter. Wrong bore means the part is unusable — no adapter fixes it.

Bore Dia. 2
number · in or mm
0.875 in (7/8 in)

Couplings routinely join two different shaft sizes. A single 'bore' field forces buyers to open the PDF to confirm the second end.

Bore Type
enum
Finished bore, keyed

Separates finished keyed bores from rough stock hubs the buyer must machine, and from keyless taper and clamp fits. Different buyer entirely.

Keyway Size
text
3/16 x 3/32 in

The key must match the shaft's existing keyway. Dimensions follow AGMA 9002 (inch) or DIN 6885 / AGMA 9112 (metric).

Nominal (Rated) Torque
number · Nm (or in-lb)
16.3 Nm (144 in-lb)

The selection number once a service factor is applied. Determines whether the coupling survives the drive it is bolted into.

Max. Speed
number · rpm
9,000 rpm

Hard ceiling set by hub material, element, and balance. A bronze insert caps near 250 rpm; the same size in NBR runs to 9,000 rpm.

Manufacturer Part Number (MPN)
identifier
68514411087

The join key for interchange, punchout catalogs, and supplier price files. Buyers paste it straight into search.

Differentiating

What buyers actually compare on. This is where catalogs win or lose the filter.

Insert / Element Material
enum
NBR (Buna-N)

Sets torque, temperature, chemical resistance, and reversing suitability. Hytrel carries roughly 3x NBR torque but dislikes frequent reversing.

Hub Material
enum
Sintered iron

Drives speed rating, corrosion suitability, inertia, and price. Stainless and aluminum hubs are washdown and low-inertia plays.

Max. Parallel (Offset) Misalignment
number · mm (or in)
0.38 mm (0.015 in)

What the buyer checks against their laser alignment reading. Published per size and element, and the reason flexible couplings exist.

Max. Angular Misalignment
number · degrees
1°

Rated separately from parallel offset and usually the tighter constraint on close-coupled pump and gearbox installs.

Compliance & identifiers

Standards, regulatory data, and the identifiers channels reject you for missing.

Bore & Keyway Standard
enum
ANSI/AGMA 9002-C14 (inch)

Tells the buyer the bore tolerance and keyway fit are commercially standard, not special. Cited on OEM and API-spec'd RFQs.

Potential Unbalance Class (AGMA 9000-D11)
enum
Class 9

Needed above ~1,800 rpm: Class 10 for 1,800–5,000 rev/min, Class 11 above 5,000. Absent, the SKU is unquotable on rotating-equipment specs.

ATEX Marking
enum
II 2GD c T4

Required for EU explosive atmospheres under 2014/34/EU. Ex SKUs use conductive inserts and carry de-rated torque, so they are distinct parts.

GTIN / UPC
identifier
00685144110870

Marketplace and punchout gate. Amazon Business and most contract catalogs will not list a SKU without one.

Country of Origin
enum
United States

Drives duty, Buy American / TAA eligibility on government and utility contracts, and customs paperwork on export orders.

The fields that aren't in the schema at all

What most shaft couplings catalogs are missing.

The table above is the schema most catalogs already have. These are the attributes that usually aren't in it — each one surfaced by a signal from the live market rather than by an audit of what's already there. This is what Anglera's Schema Foundry does on a real catalog, in this category.

Marketplace signal
+ Sold-As / Assembly Completeness

McMaster's spider coupling pages state that two hubs, a spider, and a cover are each sold separately. Most distributor catalogs list 'L095 Coupling' with no field saying which piece the SKU is.

Buyer orders one line expecting a coupling and receives a single hub. Return, reship, and a machine that stays down through the second shipment.

Supplier signal
+ Element Operating Temperature Range

Manufacturer handbooks publish spider limits by material — NBR -40 to 100 °C, Hytrel to roughly 121 °C, bronze far higher. SKU records carry the material name and no temperature field.

A standard NBR spider goes into a hot pump or compressor, hardens, and fails early. Comes back as a warranty claim against the distributor.

Search signal
+ Interchange / Competitor Cross-Reference

Buyers search 'L095 equivalent' and 'TB Wood's to Lovejoy cross' because size codes are near-universal across brands. Most catalogs have no interchange field to match those queries against.

Zero results on a part you stock under another brand. The buyer assumes you don't carry it and calls whoever ranks for the cross-reference.

Competitor signal
+ Torsional Stiffness / Backlash

Servo coupling filter rails expose torsional stiffness and zero-backlash construction. The same catalogs' industrial coupling records carry neither, so positioning applications cannot filter.

Motion-control RFQs go to a specialist. The stock is technically suitable but invisible to the only filter that buyer uses.

Supplier signal
+ Max. Finished Bore (rough stock hubs)

Rough stock and pilot bore hubs are sold to be machined, but the maximum bore they can be finished to sits in the catalog rating table, never on the SKU.

Shop bores past the limit and scraps the hub, or over-buys the next size up. Either way the line can't answer 'will this fit my shaft'.

How Schema Foundry finds these

Messy in, governed out.

The same value, spelled every way power transmission & bearings suppliers spell it. A filter only works once they agree.

Coupling Type
JawJaw TypeL-TypeSpider CouplingCurved JawElastomeric Coupling
Jaw (Elastomeric Insert)

McMaster sells them as Spider Couplings, Lovejoy as L Type, Grainger as Jaw Couplings. One part, four names, four broken filters.

Bore Dia. 1
5/8.6250.625 in5/8 in15.88mm16mm
0.625 in (15.88 mm)

5/8 in is 15.88 mm, not 16 mm. A supplier who rounds describes a hub that will not hold the shaft to the AGMA 9002 fit.

Insert / Element Material
NBRBuna-NBuna NNitrileSOXRubber
NBR (Buna-N)

Lovejoy prints SOX on the box for its NBR spider. Loaded literally it becomes a separate material value and splits the filter.

Nominal (Rated) Torque
144 in-lb144 in.lbs12 ft-lb16.3 Nm16.3 N-m1.66 kgf-m
16.3 Nm

in-lb and ft-lb differ by 12x. Mixed unit strings in one torque column silently mis-size couplings and defeat range filters.

What buyers ask

Every one of these should be answerable from the attributes above. If it isn't, that's a gap.

  • Is this a complete coupling or just one hub?
  • Do I order the spider separately, and which one fits an L095?
  • Will this handle 3 HP at 1,750 RPM with a 2.0 service factor?
  • Can I get this size with a 24 mm bore instead of 7/8 in?
  • What's the max temperature for the NBR spider? My pump housing runs hot.
  • My laser alignment reads 0.010 in offset — will this coupling take it?
  • What's the Lovejoy equivalent of a TB Wood's L095?
  • Is the rough stock hub big enough to bore out to 1-1/8 in?

What channels require

The same SKU, different mandatory fields per destination.

Distributor's own faceted catalog
Coupling TypeCoupling Size / Series DesignationBore Dia. 1Bore Dia. 2Bore TypeNominal (Rated) Torque
Amazon Business
GTIN / UPCManufacturer Part Number (MPN)BrandCoupling TypeBore Dia. 1Country of Origin
SAP Ariba / Coupa punchout & CIF catalogs
Manufacturer Part Number (MPN)UNSPSC codeGTIN / UPCCountry of OriginUnit of measureCoupling Type
OEM rotating-equipment RFQ (API 671, ISO 14691)
Nominal (Rated) TorqueMax. SpeedPotential Unbalance Class (AGMA 9000-D11)Bore & Keyway StandardMax. Angular MisalignmentATEX Marking

Shaft Couplings data, in practice

Should I filter on nominal torque or peak torque?

Neither alone. Nominal torque is HP x 63,025 / RPM in in-lb — that is the application torque, not the selection torque. Multiply it by an AGMA service factor: roughly 1.0–1.5 for steady loads like centrifugal pumps and fans, 2.5–4.0 for reciprocating compressors, jam-prone conveyors, and frequently reversing drives. Grainger splits the spec three ways — Max. Torque, Dynamic Torque (Reversing), and Dynamic Torque (Non-Reversing) — because a coupling that survives 144 in-lb steady will not survive 144 in-lb reversing. Carry all three when the manufacturer publishes them; a single 'Torque' column forces the buyer to guess which one they are looking at.

Why do bore dimensions cause so many returns here?

The same hub gets described in two measurement systems and three formats. 5/8 in is 15.88 mm; a supplier who rounds it to 16 mm has described a hub that will not hold a 5/8 in shaft to the fit AGMA 9002 specifies. Add fractional (5/8), decimal (.625), and unit-suffixed (0.625 in) spellings across a multi-brand catalog and a bore filter returns partial results — the buyer concludes you do not stock it and leaves. Normalize to one governed value per bore, carry both measurement systems on the record, and cite AGMA 9002 (inch) and AGMA 9112 (metric) as the tolerance reference rather than restating tolerances per SKU.

Does an ATEX rating change the published torque?

Yes, and this is the trap. Qualifying a coupling to ATEX 2014/34/EU typically de-rates published torque and misalignment capacity by around 30 percent, and jaw couplings need conductive urethane inserts rather than standard ones to guarantee a path to ground for electrostatic charge. The ATEX version of a size is therefore not the standard version with a certificate attached — it is a different part with different ratings and a different insert. A catalog that carries one torque number per size plus an ATEX boolean will over-promise on every Ex SKU it lists, and the error only surfaces when a specifying engineer checks the number against the manufacturer's Ex datasheet.

What separates a general-purpose from a special-purpose coupling record?

Scope and speed. ISO 14691 covers general-purpose flexible couplings — gear, metallic flexible-element, and elastomeric types — for stiff-shaft machines at speeds up to about 4,000 r/min. API 671, co-published as ISO 10441, covers special-purpose couplings for continuous-duty, high-speed service in petroleum, petrochemical, and gas plants. The catalog consequence is concrete: API 671 SKUs have to carry balance and unbalance data that general-purpose SKUs never need. AGMA 9000-D11 is the usual vocabulary — above 1,800 up to 5,000 rev/min calls for Class 10, above 5,000 rev/min Class 11. With no unbalance class field, the SKU cannot be quoted against those specs at all.

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