How it connects
Coupler jaws are pushed over the ball head and grip behind it; grease pressure unseats the internal spring-loaded check ball. The mounting end is a separate male thread (taper or straight) into the part.
Male and female halves
The fitting is the male half (nipple); the grease gun coupler is the female half. This port is the male nipple.
Usually connects to
- Standard grease-gun hydraulic coupler, including four-jaw clip-on, lock-on and push-on types
- Grease-gun needle adapter
Common sizes
- Standard hydraulic grease heads are roughly 6.5 mm (1/4 in class) diameter for common gun couplers.
- Mounting threads include 1/4-28 taper/SAE-LT/UNF descriptions, 1/8-27 NPT/PTF, 1/4-18 NPT, 10-32, 5/16-24, 1/8 BSP, M5 × 0.8, M6 × 1, M8 × 1, M10 × 1 and M12 × 1.5.
- Bodies may be straight, 45° or 90°; match mounting threads separately from the head.
Where it is used
Machinery, bearings and pivotsAutomotive suspension/steering/drivelineValve stems/bodiesCasters/wheel bearingsFarm/construction equipment
Variations
- Straight, 45° or 90° nipple
- Drive-in/press-in
- Thread-forming
- Flush type
- Larger button-head (different coupler)
How to recognise it
Small hex body with a short neck and a rounded ball head about 6.5 mm across, with a tiny hole and visible check ball at the tip; male thread below the hex. The sample's head OD 6.5 mm / neck 4 mm fits the standard hydraulic head.
Often confused with
| Confused with | How to tell them apart |
|---|---|
| Button-head / flush-type grease fitting | Button-head has a large flat round head (about 5/8 in) and needs a slide-on button coupler, not a jaw coupler. Button-head fittings have a large flat head, and flush types sit level with the surface. Each needs its own coupler. |
| Flush-type grease fitting | Flush type sits level with the surface and needs a pointed needle/flush adapter; no protruding ball head. |
| Bleeder / drain valve | Bleeders have a conical tip with a side hole and no ball head with check ball; they're opened by turning. |
| Button-head grease nipple (DIN 3404) | It has a large flat round head (about 16 or 22 mm) and needs a slide-on button-head coupler. The hydraulic type has a small domed ball head of about 6.5 mm. |
| Flush-type grease fitting (DIN 3405) | It sits flush with the surface and has no protruding head. It needs a pointed needle or flush-type adapter. |
Also called
Zerk fittingAlemite fittinghydraulic grease fittinggrease zerklubrication fittingDIN 71412 grease nippletype H grease nipple; hydraulic grease nipplelubrication nipple
Good to know
This is the lubrication interface (grease nipple head). The fitting's mounting thread into the valve body is a separate interface and was not specified for the sample part; don't classify the port as an NPT branch based on the head alone.
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