This page covers the M8 grease nipple, an M8x1.0 metric grease fitting in straight, 45°, 90°, button-head, and flush configurations. For the full DIN 71412 size family (M6, M10) see the DIN 71412 grease nipple family page; for stainless steel material selection, see the stainless grease nipple page. This page is the M8 thread reference for dimensions, forms, torque, couplers, and replacement signals.
What the M8x1.0 Design Covers
The thread is M8x1.0, the fine metric pitch on most small and mid-size lube points. A spring-loaded ball check opens during injection and self-closes when the coupler is removed, limiting leaks and contamination. Standard hydraulic-type couplers seal on the conical head. The table below lists core dimensions.
| Parameter | Value |
|---|---|
| Thread | M8x1.0 fine metric; minimum engagement 8 mm |
| Hex | 11 mm across flats (typical) |
| Overall length | 15 to 25 mm by configuration; straight 15 to 20 mm |
| Ball diameter | 3.5 to 4.5 mm |
| Bore diameter | 1.8 to 2.5 mm |
| Straight passage | 2.0 to 3.0 mm |
| Installation torque | 8 – 12 Nm |
| Injection pressure | Compatible with grease gun injection pressure up to 400 bar |
| Temperature, plated steel | -40°C to +200°C |
| Configuration | Form | Feature | Dimensional note |
|---|---|---|---|
| Straight | Form A | Axial access for bearings, pivots, and open points | Overall length 15 to 20 mm; internal passage 2.0 to 3.0 mm |
| 45° | Form B | Angled access with +/-2° angle tolerance | Minimum wall thickness 1.5 mm at the bend |
| 90° | Form B | Perpendicular outlet for compact assemblies | Pressure drop about 5 to 10% higher than straight |
| Button head | DIN 3404 | Low profile head for guarded or rotating points | Head diameter 10 to 12 mm; 2 to 4x the flow of a standard ball head |
| Flush | Flush style | Sits 0 to 2 mm proud of the mounting face | Needs a counterbore and a flush or needle-nose coupler |
Choosing the Right Configuration
Straight Form A suits axial access to open bearings and pivots; 45° and 90° forms suit angled and blocked approaches. Button-head fittings need a dedicated button-head coupler; flush fittings need a counterbore plus a flush or needle-nose coupler and protect the head from impact damage.
Material, Temperature, and Grease Compatibility
The standard build is zinc-plated low-carbon steel (C10/C15 grade) with a 5 to 15 micron zinc layer; the plated steel range is -40°C to +200°C. Stainless options in 304 (1.4301) and 316 carry their own pressure and temperature ratings; review the stainless grease nipple page first. The shell is HRB 70 – 85 and the ball is HRC 58 – 62. The fittings accept NLGI #0 to #3 greases on lithium, calcium, or complex soap bases, with #2 the most common; mineral oil-based and synthetic greases both work.
Installation and Verification
A standard wrench fits the 11 mm hex, and installation torque is 8 – 12 Nm. Check the pitch with a thread gauge before ordering: M8x1.25 is special order, and metric and inch threads are not interchangeable. See the grease fitting types guide for a broader comparison of fitting forms.
Replacement Signals
There is no fixed service interval; judge by condition. If grease seeps at the head after coupling, the ball check is no longer seating. Cross-threaded or galled threads will not hold torque. A cracked or deformed head will not seal reliably. In corrosive environments, inspect plated steel for coating breakdown and pitting.
Limitations to Note Before Ordering
Special-order thread: M8x1.25 is special order only; confirm the pitch before ordering.
Dedicated couplers for special heads: Button-head and flush fittings each need a dedicated coupler; a standard hydraulic coupler does not fit them.
Stainless variants follow different ratings: Stainless builds carry their own pressure and temperature ratings; do not apply plated steel figures to them.
Thread system boundaries: Metric and inch threads cannot be interchanged; a thread gauge check is the only reliable identification.
If your application sits outside these limits, contact our team to confirm the right M8 fitting build.
Frequently Asked Questions
How do I tell M8x1.0 from M8x1.25?
Use a metric thread gauge and count the pitch: M8x1.0 is standard, M8x1.25 is special order only. Metric and inch threads are not interchangeable.
Which configuration should I choose: straight, 45°, 90°, button head, or flush?
Match the fitting to coupler access: straight for axial access to bearings and pivots, 45° for a partially blocked approach, 90° for perpendicular access, button head for guarded or rotating points, flush for faces exposed to impact.
Why will a standard coupler not engage a button-head fitting?
Button-head fittings follow DIN 3404 with a larger, flatter head of 10 to 12 mm and 2 to 4x the flow of a standard ball head, so a standard hydraulic coupler cannot grip them.
Where are flush fittings used?
Flush fittings sit 0 to 2 mm proud of the mounting face inside a counterbored hole, keeping external surfaces clear of impacts; they pair with flush or needle-nose couplers.
What wrench size and torque do I need?
A standard wrench fits the typical 11 mm hex; installation torque is 8 – 12 Nm. Stop in that range, since over-tightening can gall the threads.
What grease gun pressure are these fittings compatible with?
They accept grease gun injection pressure up to 400 bar, the family-wide rating; a standard hydraulic coupler seals on the conical head.
When is zinc-plated steel not enough?
In washdown, marine, or other corrosive exposure, plated steel pits and loses coating over time; compare 304 and 316 stainless options on the stainless grease nipple page.
What grease grades work with M8 grease nipples?
NLGI #0 to #3 greases on lithium, calcium, or complex soap bases, with #2 the most common; both mineral oil-based and synthetic greases are accepted.
When should I replace the fitting?
Replace when the ball check no longer seats and grease seeps at the head, when threads are damaged, the head cracks or deforms, or the fitting keeps loosening; in corrosive environments, also check plated fittings for pitting.
Who supplies these M8 grease nipples?
IsoHiTech Lubrication Systems is a lubrication equipment supplier founded in 2023, engineering since 2006. For M8x1.0 or special-order M8x1.25 fittings across all five configurations, see our grease line fittings range, send us your application details, or write to inquiry@isohitech.com.
