Overview
The M12 x 1.25 grease nipple is a metric zerk fitting: a 12 mm ISO metric thread with a 1.25 mm pitch, a 14 mm hex, and a spring-loaded ball check valve that opens under gun pressure and seals when the coupler is removed. It gives a grease gun a secure connection point on machinery built to metric threading.
The standard configuration is a straight body in zinc-plated carbon steel, 17.5 mm long with a 3.5 mm bore. Angled (45°/90°), swivel, and stainless versions are options – confirm at order. Declared working pressure is 10,000 PSI (689 bar); the DIN 71412 head accepts a standard hydraulic coupler.
Specifications
| Parameter | Specification |
|---|---|
| Thread | M12 x 1.25 (ISO metric) |
| Hex size | 14 mm |
| Overall length | 17.5 mm (straight body) |
| Internal bore | 3.5 mm |
| Minimum thread engagement | 8 mm |
| Working pressure (declared spec) | 10,000 PSI (689 bar) |
| Burst pressure (declared spec) | 15,000 PSI (1,034 bar) |
| Check valve opening pressure | 50-75 PSI |
| Flow | 2-4 cc per pump stroke (standard grease gun) |
| Tightening torque | 15-20 Nm (do not exceed 25 Nm) |
| Installation tool | 14 mm socket or wrench |
| Temperature range | -40°C to +204°C |
| Material | Zinc-plated carbon steel (standard); stainless steel option – confirm at order |
| Body variants | Straight (standard); 45°, 90°, swivel – confirm at order |
| Head form | DIN 71412 hydraulic type |
M12 x 1.25 or M12 x 1.5: Check the Pitch Before You Order
M12 x 1.25 and M12 x 1.5 share the same 12 mm diameter but are not interchangeable: the pitch differs, and forcing a mismatch cross-threads both parts and leaves a leak path. If your port is M12 x 1.5, that variant is confirm at order.
To identify your thread: measure the major diameter (12 mm for M12), then verify the pitch with a thread pitch gauge. No gauge at hand? Measure across 10 thread crests: 12.5 mm means a 1.25 mm pitch, 15 mm means a 1.5 mm pitch.
| Thread | 10-crest measurement | Status here |
|---|---|---|
| M12 x 1.25 | 12.5 mm | This page |
| M12 x 1.5 | 15 mm | Not interchangeable – confirm at order |
Applications
- Industrial machinery: bearing housings, gearboxes, and motor lubrication points on metric-threaded equipment.
- Construction and agricultural equipment: pivot points, pins, and bushings on machines built to ISO metric threads.
- Automotive and fleet: chassis and linkage points tapped M12 x 1.25.
- Hydraulic equipment: cylinder pivots and valve blocks with metric ports.
- General maintenance: replacement fittings – verify the pitch first.
Installation
- Confirm the port thread is M12 x 1.25 (see above); never force a mismatched pitch.
- Clean the threaded hole and remove burrs or old grease so the fitting seats squarely.
- Thread the nipple in by hand; if it does not start smoothly, stop and re-check the pitch.
- Tighten with a 14 mm socket or wrench to 15-20 Nm. Do not exceed 25 Nm.
- Pump grease and confirm the check valve opens and the thread joint stays dry.
For angled, swivel, or stainless versions, request a quote with your thread and body requirements.
Maintenance
Inspect regularly: keep the head clean so the coupler seats fully, clear a blocked bore, and replace the nipple if the ball check stops sealing, the threads strip, or the hex rounds off. Replacement is condition-based, not calendar-based; frequency depends on environment and grease cleanliness.
FAQ
What is an M12 x 1.25 grease nipple?
A metric zerk fitting with a 12 mm thread at 1.25 mm pitch and a built-in ball check valve. A grease gun coupler clips onto its DIN 71412 head to deliver grease into the lubrication point.
What does M12 x 1.25 mean?
M12 is a 12 mm ISO metric thread; 1.25 is the pitch in millimeters between thread crests. Both numbers are needed – the diameter alone is ambiguous.
Is M12 x 1.25 interchangeable with M12 x 1.5?
No. Same diameter, different pitch. A mismatched fitting cross-threads and leaks. Measure the pitch before ordering; if your port is M12 x 1.5, that version is confirm at order.
Why choose M12 instead of M10?
The larger thread gives more holding strength in the port and suits heavier housings – it does not mean more grease flow, since flow is set by the bore (3.5 mm here). For smaller points see our M10 grease nipples.
Is this a standard grease gun head?
Yes. The head follows DIN 71412 hydraulic type, so standard grease gun couplers clip on without adapters.
What is the difference between working and burst pressure?
Working pressure is the declared continuous rating: 10,000 PSI (689 bar). Burst pressure is the declared failure point: 15,000 PSI (1,034 bar). Convention treats burst as design margin, not permission to run above the working rating; the real limit is set by your gun and hose.
What does 2-4 cc per pump stroke mean in practice?
With a standard grease gun, each stroke pushes roughly 2-4 cc of grease through this fitting, so ten strokes deliver about 20-40 cc. Count strokes, not time, when relubricating.
Which body variant should I choose?
Straight is standard and suits head-on coupler access. 45° and 90° bodies help where clearance is tight; swivel eases coupler alignment; stainless suits corrosive environments. All variants are confirm at order. For other fitting styles, see our grease fitting types guide.
How tight should an M12 grease nipple be?
Hand-start the thread, then tighten with a 14 mm socket to 15-20 Nm. Do not exceed 25 Nm – over-tightening can strip the port or crack the fitting body.
How do I confirm my thread or order a variant?
Measure the 12 mm diameter, verify the 1.25 mm pitch, and check clearance for a straight or angled body. For smaller metric points, see the M6 DIN 71412 nipple. To confirm thread, material, or body variant, contact our team for a quote – IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006; inquiry@isohitech.com.
