What a Metric Grease Fitting Is
A metric grease fitting is a threaded nipple that lets a grease coupler push lubricant past a spring-loaded ball check into a bearing housing. The ball reseats after each dose and keeps contamination out. Thread match decides everything: a wrong thread starts, then binds or strips, costing both the fitting and the housing.
Metric Size Chart
Eight thread sizes cover most machines, from M6x1.0 up to M16x1.5. Hex width across flats runs 6-10 mm by size, and these are 10000 PSI class fittings.
| Metric thread | Typical pairing |
|---|---|
| M6x1.0 | light housings |
| M8x1.0 | light housings and compact machines |
| M8x1.25 | compact machinery |
| M10x1.0 | general machinery |
| M10x1.5 | general machinery |
| M12x1.5 | heavy equipment |
| M14x1.5 | heavy equipment |
| M16x1.5 | large frames |
Single-size pages cover the M8 grease nipple, the M10 grease nipples, and a 12 mm 1.25 mm metric zerk variant for less common pairings.
Head Forms in Plain Words
Conical is the standard ball-check head that most grease guns fit. Button is a low domed head that sits below the surrounding surface and shrugs off knocks. Flush sits protected inside a countersink. The coupler must match the head form, not only the thread, so check the head before ordering. Full head-form geometry lives on the metric grease nipple family page.
Body Angles and Materials
Bodies come straight, 45 degree, or 90 degree so the fitting points where a grease gun can actually reach; choose by access, not preference. Zinc-plated carbon steel suits dry plant, stainless steel suits washdown and corrosive sites, and brass suits softer housings and marine air. The stainless steel grease nipples page covers the washdown range.
Identify an Unknown Fitting
Work through four steps before you order a replacement:
- Measure the major diameter with calipers.
- Count crests over 10 mm to gauge pitch: about ten crests means 1.0, eight means 1.25, and six or seven means 1.5.
- Check the head form: conical, button, or flush.
- Test-fit a known coupler by hand before you wrench anything.
Near-Miss Traps: Metric vs UNF
Some UNF threads are close enough to metric to start, then bind or cross-thread. The classic pairs:
| Metric | Commonly confused UNF | Why it almost fits |
|---|---|---|
| M6x1.0 | 1/4-28 | near-identical major diameter |
| M8x1.25 | 5/16-24 | diameter within a few hundredths |
| M10x1.5 | 3/8-24 | threads engage 1-2 turns then bind |
| M12x1.5 | 1/2-20 | starts, then cross-threads |
British pipe threads also look close to metric sizes and are not interchangeable, so measure instead of assuming. If you are unsure after measuring, contact us for a quote with your identification notes and we will confirm the thread.
Frequently Asked Questions
What is a metric grease fitting?
A threaded nipple with a spring-loaded ball check that lets a grease gun push lubricant into a housing. The ball seats after dosing and keeps contamination out.
How do I identify a fitting on a machine?
Measure the major diameter, then count crests over 10 mm to gauge the pitch. Check the head form and test-fit a known coupler by hand before ordering.
Is M8x1.0 the same as M8x1.25?
No, they are not interchangeable. The diameter matches but the pitch differs: about ten crests over 10 mm means 1.0, and eight means 1.25.
Is metric the same as UNF?
No. Several pairs are near-misses that start and then bind or cross-thread; check the 1/4 UNF grease nipple reference before mixing threads.
Will a standard coupler fit every head form?
Conical heads take the standard coupler, but button and flush heads need matched couplers. Match the coupler to the head form, not only the thread.
Straight, 45 degree, or 90 degree?
Pick by access, not preference. Choose straight where the gun reaches head-on, and angled where clearance is tight.
Steel, stainless, or brass?
Zinc-plated steel suits dry plant, stainless suits washdown and corrosive sites, and brass suits softer housings. See the stainless range for washdown duty.
Do M14 and M16 sizes exist?
Yes, both are heavy-equipment sizes for large frames. Confirm availability and hex size at ordering.
How do I order the right fittings?
List thread size, pitch, head form, material, and body angle for each position, then ask our team to confirm. Send the list through contact our team for a quote and we reply with a matched set.
Who builds these metric grease fittings?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
