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Grease Nipple Thread Identifier
Identify the correct Zerk fitting for your fleet or plant machinery — metric, UNF and BSP standards.
Log lubrication points and service intervals against every asset — free.
Select Your Nipple Type
Thread Standard
1/4"-28 UNF
OD (mm)
6.35 mm
Hex AF
10 mm
Common on
Most UK & European fleet & plant machinery — JCB, Case, New Holland, Massey Ferguson (post-1985), Claas
The most common grease nipple worldwide. Fits a 10 mm AF spanner or 10 mm hex socket.
Full Size Reference — All Standards
Click any row to select it above
| Type | Thread | OD (mm) | Pitch / TPI | Hex AF | Common |
|---|---|---|---|---|---|
| Imperial (UNF) | 1/4"-28 UNF | 6.35 | 28 TPI | 10 mm | Common |
| Metric | M6 × 1.0 | 6.00 | 1.0 mm | 9 mm | Common |
| Metric | M8 × 1.0 | 8.00 | 1.0 mm | 11 mm | – |
| Metric | M10 × 1.0 | 10.00 | 1.0 mm | 14 mm | – |
| BSP | 1/8" BSPP | 9.73 | 28 TPI | 14 mm | – |
| Imperial (UNF) | 7/16"-20 UNF | 11.11 | 20 TPI | 11 mm | – |
| Metric | M5 × 0.8 | 5.00 | 0.8 mm | 8 mm | – |
How to Identify Your Grease Nipple Standard
1
Measure the hex size
Use a spanner or vernier caliper across the flats:
- 8 mm — M5 metric
- 9 mm — M6 metric
- 10 mm — 1/4" UNF (most common)
- 11 mm — M8 or 7/16" UNF
- 14 mm — M10 or 1/8" BSP
2
Count the threads
Use a thread pitch gauge against the thread flank.
- 28 TPI — 1/4" UNF or 1/8" BSP
- 20 TPI — 7/16" UNF
- 1.0 mm pitch — M6, M8 or M10 metric
- 0.8 mm pitch — M5 metric
3
Machine brand & era
Use the manufacturer and build year as a guide:
- Most machinery — 1/4" UNF
- Modern EU (post-2010) — likely M6
- Older British (pre-1985) — 1/8" BSP
- American imports — 7/16" UNF
Frequently Asked Questions
Most Massey Ferguson tractors built from the mid-1980s onwards use the 1/4"-28 UNF (standard Zerk) grease nipple. Older UK-built models from the 1960s and 1970s often used 1/8" BSP, which takes a 14 mm AF spanner. Measure the hex across the flats: 10 mm = 1/4" UNF, 14 mm = 1/8" BSP.
Both are around 6 mm at the thread OD but are not interchangeable. The 1/4" UNF uses an imperial thread (28 TPI) and a 10 mm AF spanner. The M6 × 1.0 uses a metric thread (1.0 mm pitch) and a 9 mm AF spanner. Installing the wrong nipple damages the threads — use a thread pitch gauge to confirm: 28 TPI = UNF, 1.0 mm pitch = metric.
Apply penetrating oil and leave for 10–15 minutes. Use a correctly sized spanner to avoid rounding the hex. If rounded, use grease nipple removal pliers or an extractor socket. For a nipple broken flush, drill through the centre with a left-hand bit and extract with a screw extractor, then clean the threads with a tap before fitting the replacement.
No — despite sharing 28 TPI, BSP and UNF have different thread diameters and forms and will not fit each other's holes. To convert from BSP to UNF, re-tap the hole with a 1/4"-28 UNF tap or fit a BSP-to-UNF adaptor plug.
Always check the manufacturer manual first. As a general guide: linkage pins and pivots every 50–100 hours, front axle king pins every 50 hours, PTO shafts every 8 hours in use, loader pivot pins every 10 hours in use, and universal joints every 50 hours.
A grease nipple (Zerk fitting) is a one-way valve — a spring-loaded ball sits against a seat. Pressing a grease gun onto it pushes the ball off its seat, letting grease flow through; releasing the gun lets the spring reseal it. A nipple that will not take grease usually has a stuck ball — try tapping it with a centre punch or replace it.
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