Tuthill 1L519 Three-Piece Coupling for L Series Lubrication and Transfer Pumps
The Tuthill 1L519 is the three-piece drive coupling used to tie an electric motor shaft to the shaft of a Tuthill L Series internal gear pump. It is a simple assembly by design: two hubs and a center element that transmits torque between them. That center element is what does the quiet work, taking up the small linear and angular offsets that exist between any two shafts once a pump and motor are bolted to a common base. Without it, that offset lands squarely on the pump's bearings and mechanical seal, and it shortens the life of both.
L Series pumps show up in a wide spread of equipment, and very little of it has anything to do with boats. They circulate oil through machine tool spindles and gearboxes, feed burners on industrial oil-fired heating systems, move fuel and light oils in transfer service, and keep lubrication loops running on compressors, presses, and reduction drives. They handle fluids from roughly 32 SSU up to 5000 SSU, run to 500 PSI, and tolerate temperatures well above what most pumps see in service. Whatever the installation, the coupling is the piece that stands between the motor and the pump, and it is the piece most often replaced during a rebuild.
Because the 1L519 is a wear item rather than a permanent component, it is worth keeping one on the shelf alongside a spare seal kit. The center element eventually hardens, cracks, or wears from continuous duty, vibration, and heat, and the symptom is usually noise, a visible wobble, or a pump that no longer holds pressure. Replacing the coupling is a short job with basic hand tools and restores the drive train to correct operation without touching the pump internals. Ordering by the 1L519 part number ensures you receive the correct three-piece assembly for the L Series frame rather than a generic substitute that may not match hub bore or overall length.
Key Features
- Three-piece coupling assembly consisting of two hubs and a replaceable center drive element
- Accommodates slight linear and angular shaft misalignment between motor and pump
- Protects pump bearings and mechanical seal from side loading and vibration
- Genuine Tuthill part number 1L519 for correct fit on L Series pump frames
- Field replaceable with basic hand tools, no pump disassembly required
- Dampens torsional shock at motor start-up and during pressure surges
- Recognized under National Stock Number 3010-00-408-7963 for defense and government procurement
- Compact overall length suits close-coupled motor and pump base arrangements
Applications
- Machine tool spindle and slideway lubrication systems
- Gearbox and reduction drive oil circulation loops
- Industrial oil burner feed and fuel oil supply systems
- Light oil and fuel transfer service
- Filtration and oil conditioning skids
- Compressor and press lubrication packages
- Hydraulic power unit charge and circulation duty
- Process heating and heat transfer fluid circulation
- General industrial pump and motor drive replacement and rebuild work
Specifications
- Manufacturer: Tuthill Pump Group
- Part Number: 1L519
- Product Type: Flexible shaft coupling, three-piece assembly
- Pump Series: Tuthill L Series internal gear pumps
- Design Type: Internal gear flex
- Overall Length: 1.000 in nominal
- Outside Diameter: 1.250 in nominal
- Function: Motor shaft to pump shaft torque transmission
- Misalignment: Accommodates slight linear and angular offset
- NSN: 3010-00-408-7963
- CAGE Code: 61178
- Sold As: Each, complete three-piece assembly
- Shelf Life: Non-deteriorative
Frequently Asked Questions
Q: How do I know when the 1L519 coupling needs to be replaced?
A: Listen and look. A worn coupling usually announces itself with a knocking or chattering noise at the pump end, a visible wobble in the drive when the unit is running, or rubber debris collecting inside the coupling guard. Loss of pressure or intermittent flow can also point to a center element that is slipping rather than driving.
Q: Can I install the coupling without pulling the pump off its base?
A: In most installations, yes. The motor is loosened and backed away far enough to expose the coupling, the old assembly comes off the two shafts, and the replacement goes on. Check shaft alignment with a straightedge before retightening the motor feet, since a coupling forgives small offset but will not correct a badly seated motor.
Q: Does the 1L519 fit every model in the Tuthill L Series range?
A: It is the standard three-piece coupling for L Series frames, but bore size varies with the motor shaft diameter on your particular unit. Confirm the motor shaft diameter and the pump shaft diameter against your pump's parts breakdown before ordering, especially on older or rebuilt assemblies.
Q: What happens if the coupling is installed with the hubs too tight against each other?
A: The hubs need a small gap so the center element can flex and so neither shaft is loaded axially. Butting the hubs together transfers thrust directly into the pump bearings and defeats the purpose of a flexible coupling. Set the gap per the pump manual and lock the setscrews on the shaft keyways.
Q: Should I keep a spare on hand?
A: For any pump in continuous or critical duty, it is sensible. The coupling is inexpensive relative to the downtime a failed drive causes, it does not degrade in storage, and it pairs naturally with a spare mechanical seal so a single planned shutdown can cover both wear items.
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