Grease Nipples

Grease Nipple Quick Reference — Thread & Configuration

Grease nipples (Zerk fittings) are the inlet valves through which grease enters a bearing or lubrication point. Selection requires matching THREAD (to the tapped hole in housing), CONFIGURATION (straight, 45°, 90°, drive-in) and STANDARD (SAE J534 for Zerk, JIS for Japanese equipment). AIMS stocks all common combinations for industrial, automotive and agricultural applications.

Configuration options: Straight (most common, vertical access), 45° angled (restricted access), 90° angled (sideways access on flat surfaces). Always match the coupler on your grease gun to the nipple — see grease couplers. For full background on nipple identification, see our grease nipple & Zerk fitting guide. Companion ranges: grease guns, lubrication.

Grease Nipples

Grease nipples — also known as Zerk fittings, lubrication fittings, or grease fittings — are the inlet valves through which grease is injected into a bearing, joint, or lubrication point. The nipple contains a spring-loaded ball check valve that holds grease in the fitting until the grease gun coupler is attached and pressure applied; when the coupler seals on the nipple head and grease pressure builds, the ball lifts off its seat and grease flows into the lubrication cavity. AIMS Industrial supplies grease nipples in straight, angled, and drive-in configurations for all industrial and automotive lubrication applications.

Thread Types and Sizes

Grease nipple threads must match the tapped hole in the housing or fitting. The most common thread sizes in Australian industry are:

• 1/8" BSP (G1/8): The most common size in general industrial and agricultural equipment. Australian metric housings are typically tapped to this size for standard hydraulic nipples.
• 1/4" BSP (G1/4): Larger fittings for higher-capacity grease points on heavy industrial equipment, truck hubs, and large bearings.
• M6, M8, M10 metric: Common in European-designed equipment and machinery. Not interchangeable with BSP threads of similar size — confirm thread type before ordering.
• Drive-in type: Press-fit nipples without threads — pushed into a drilled hole and retained by knurled barbs. Used where threading is impractical or where the fitting must be replaceable without thread engagement.

Head Angles

Straight (0°) nipples are the standard for grease points with direct access. 45° and 90° angled nipples point the grease gun connection away from the bearing housing, allowing coupler access in confined locations where a straight nipple head would be blocked by adjacent structure. The correct angle is determined by the available access space — a 90° nipple on a bearing that is accessible from above may allow a straight-down coupler approach when a straight nipple would require working from the side.

Material Selection

Standard steel nipples suit most applications. Stainless steel nipples are specified for marine, food processing, and chemical environments where the standard steel nipple would corrode. For grease nipple selection by thread type, angle, and material, contact our team.

Grease Nipple Standards and Compatibility

The three most common grease nipple standards encountered in Australian industry are metric (M6, M8, M10 thread), imperial UNF (1/4-28 UNF being most common), and BSPT for older British-made equipment. Before ordering replacement nipples, confirm both the thread size and the head type — hydraulic, standard, and button-head nipples are not interchangeable with standard grease gun couplers. Flush-fitting nipples are specified where protruding heads create a snagging hazard or where guard clearances are tight. Having an assortment kit covering the main types and sizes is standard practice for maintenance workshops handling diverse equipment fleets.

People Also Ask — Grease Nipples

Q: What is a grease nipple?

A grease nipple (also called a Zerk fitting or lubrication fitting) is an inlet valve fitted to a bearing housing, joint, or lubrication point. It contains a spring-loaded ball check valve that holds grease in the fitting until a grease gun coupler is attached and pressure applied, allowing grease to flow into the lubrication cavity.

Q: What thread sizes do grease nipples come in?

The most common Australian industrial size is 1/8" BSP (G1/8), which suits most general industrial and agricultural equipment. Larger points use 1/4" BSP. European equipment uses metric threads — M6 × 1.0, M8 × 1.0 or 1.25, or M10 × 1.0 or 1.5. US and automotive imports often use NPT (1/8" or 1/4" NPT) or SAE J534 (5/16") threads. Drive-in types press into unthreaded holes.

Q: What head angles are available for grease nipples?

Grease nipples come in three configurations: straight (the most common, for unobstructed vertical access), 45° angled (for restricted access from above), and 90° angled (for sideways access on flat surfaces or confined spaces). The angle of the nipple has no effect on grease flow — it is chosen purely for access.

Q: Are BSP and NPT grease nipples interchangeable?

No. BSP (British Standard Pipe) and NPT (National Pipe Taper) use different thread forms, pitches, and taper angles. A BSP nipple may partially engage an NPT-tapped hole but will not seal correctly and will leak under grease gun pressure. Always confirm the thread type and standard before ordering replacement fittings.

Q: When should stainless steel grease nipples be specified?

Stainless steel grease nipples should be used wherever standard carbon steel fittings will corrode — marine, food and beverage, chemical, and outdoor agricultural equipment. Stainless fittings are also recommended where corrosion could block the ball check valve and prevent grease flow to the bearing.