Grease fitting (Zerk) thread, hex and overall height — straight and angled, button head, drive and metric DIN 71412 — where two makers’ tables agree.
A grease fitting is named by its thread (1/4-28, 1/8″ pipe, M6×1 …) and its angle — straight, 45°, 65° or 90° between the head and the thread. The head the grease gun coupler snaps onto is standard (SAE J534 inch, DIN 71412 metric); the hex and the height are the maker’s. The thread data comes from our thread pitch, metric thread and pipe thread charts.
| Thread | Type | Angle | Hex | Overall height |
|---|---|---|---|---|
| 1/4-28 | Standard | Straight | — | — |
| 1/4-28 | Standard | 45° | 3/8″ | — |
| 1/4-28 | Standard | 65° | 3/8″ | 25/32″ |
| 1/4-28 | Standard | 90° | 3/8″ | 3/4″ |
| 1/4-28 | Thread forming | Straight | — | — |
| 1/4-28 | Thread forming | 45° | 3/8″ | — |
| 1/4-28 | Thread forming | 90° | 3/8″ | — |
| 1/4-28 | Flush | Straight | — | — |
| 5/16-24 | Standard | Straight | — | — |
| 5/16-24 | Standard | 90° | — | — |
| 3/8-24 | Standard | Straight | — | — |
| 3/8-24 | Standard | 90° | — | — |
| 1/8″ NPT | Standard | Straight | — | — |
| 1/8″ NPT | Standard | 30° | — | — |
| 1/8″ NPT | Standard | 45° | 7/16″ | 57/64″ |
| 1/8″ NPT | Standard | 65° | — | — |
| 1/8″ NPT | Standard | 90° | 7/16″ | — |
| 1/8″ NPT | Button head | Straight | 5/8″ | 3/4″ |
| 1/8″ NPT | Thread forming | Straight | 7/16″ | — |
| 1/8″ NPT | Thread forming | 45° | 7/16″ | — |
| 1/8″ NPT | Thread forming | 90° | 7/16″ | — |
| 1/8″ NPT female | Standard | Straight | — | — |
| 1/4″ NPT | Standard | Straight | 9/16″ | — |
| 1/4″ NPT | Standard | 45° | — | — |
| 1/4″ NPT | Standard | 65° | — | — |
| 1/4″ NPT | Standard | 67-1/2° | — | — |
| 1/4″ NPT | Standard | 90° | — | — |
| 1/4″ NPT | Button head | Straight | 5/8″ | — |
| 1/4″ NPT | Giant button head | Straight | — | — |
| 3/8″ NPT | Standard | Straight | — | — |
| 3/8″ NPT | Button head | Straight | 3/4″ | — |
| 1/2″ NPT | Giant button head | Straight | — | — |
| Thread | Type | Angle | Hex | Overall height |
|---|---|---|---|---|
| M5×0.8 | Standard | Straight | — | — |
| M5×0.8 | Standard | 45° | — | — |
| M5×0.8 | Standard | 90° | — | — |
| M6×0.75 | Standard | 45° | — | — |
| M6×0.75 | Standard | 90° | — | — |
| M6×1 | Standard | Straight | 7 mm | — |
| M6×1 | Standard | 45° | — | — |
| M6×1 | Standard | 90° | — | — |
| M8×1 | Standard | Straight | 9 mm | — |
| M8×1 | Standard | 45° | 9 mm | — |
| M8×1 | Standard | 90° | — | — |
| M8×1.25 | Standard | Straight | — | — |
| M8×1.25 | Standard | 45° | — | — |
| M8×1.25 | Standard | 90° | — | — |
| M10×1 | Standard | Straight | 11 mm | — |
| M10×1 | Standard | 45° | 11 mm | — |
| M10×1 | Standard | 90° | 11 mm | — |
| M10×1.5 | Standard | Straight | — | — |
| M10×1.5 | Standard | 45° | — | — |
| M10×1.5 | Standard | 90° | — | — |
| M12×1.75 | Button head | Straight | — | — |
| Thread | Type | Angle | Overall height | Hex |
|---|---|---|---|---|
| 1/4-28 | Standard | Straight | 17/32″ | 5/16″ |
| 1/4-28 | Standard | Straight | 35/64″ | 5/16″ |
| 1/4-28 | Standard | Straight | 11/16″ | 5/16″ |
| 1/4-28 | Standard | Straight | 15/16″ | — |
| 1/4-28 | Standard | Straight | 1-39/64″ | — |
| 1/4-28 | Standard | 45° | 13/16″ | 3/8″ |
| 1/4-28 | Standard | 65° | 25/32″ | 3/8″ |
| 1/4-28 | Standard | 90° | 3/4″ | 3/8″ |
| 1/8″ NPT | Standard | Straight | 1-1/4″ | 7/16″ |
| 1/8″ NPT | Standard | Straight | 1-3/4″ | — |
| 1/8″ NPT | Standard | Straight | 2-5/8″ | — |
| 1/8″ NPT | Standard | 30° | 2-3/32″ | — |
| 1/8″ NPT | Standard | 45° | 57/64″ | 7/16″ |
| 1/8″ NPT | Standard | 65° | 1-7/32″ | 7/16″ |
| 1/8″ NPT | Standard | 90° | 27/32″ | 7/16″ |
| 1/8″ NPT | Button head | Straight | 3/4″ | 5/8″ |
| M6×1 | Standard | 45° | 13/16″ | — |
| Hole | Angle | Overall height |
|---|---|---|
| 1/8″ hole | Straight | — |
| 5/32″ hole | Straight | — |
| 3/16″ hole | Straight | — |
| 3/16″ hole | 65° | — |
| 1/4″ hole | Straight | — |
| 1/4″ hole | 65° | 49/64″ |
| 5/16″ hole | Straight | — |
| 5/16″ hole | 65° | — |
| 3/8″ hole | Straight | — |
Good to know
Who sets the size. Inch hydraulic grease fittings (the Zerk type) are made to SAE J534; metric ones to DIN 71412. The head that the grease gun coupler snaps onto is the same; the thread, hex and height are the fitting’s own. (Alemite, G.L. Huyett)
The 1/4-28 fitting. The common 1/4-28 fitting has the SAE-LT taper thread and goes into a 1/4-28 UNF (class 3B) straight tapped hole. (Alemite, Lincoln, G.L. Huyett)
Drive fittings. A drive fitting has no thread: it is driven into a plain untapped (drilled) hole and is sized by that hole — a 3/16″ drive fitting goes into a 3/16″ hole. It goes in with a drive fitting tool — the makers sell one for straight and one for angled drive fittings. (Alemite, Lincoln)
Thread forming fittings. A thread forming (self-tapping) fitting cuts its own thread as it is spun into an untapped hole. It can later be replaced by a standard fitting of the same thread. (Alemite, Lincoln)
Button head fittings. Button head fittings have a large flat head for heavy equipment — construction and earth-moving machines — and take a button head coupler, not the standard grease gun coupler. (Alemite, Lincoln)
Height and hex by model. Makers sell each thread and angle in several heights, and some in more than one hex. Where the makers’ tables do not all agree, the chart shows a dash: measure the fitting across the flats and from the tip of the head to the end of the thread. (Alemite, Lincoln)
Ratings come from the maker. Working pressure depends on the fitting and its maker — use the maker’s rating for that fitting. (Alemite, Lincoln)
Quick answers
- What size wrench fits a 1/4-28 grease fitting?
- An angled (45° or 90°) 1/4-28 grease fitting has a 3/8″ hex. Straight 1/4-28 fittings come in more than one hex — measure across the flats.
- What thread is a standard grease fitting?
- The common inch threads are 1/4-28 (SAE-LT taper, into a 1/4-28 UNF tapped hole) and 1/8″ pipe (1/8-27); metric fittings to DIN 71412 are M6×1, M8×1 and M10×1 and others.
- What standard covers grease fittings?
- SAE J534 for inch hydraulic (Zerk-type) grease fittings; DIN 71412 for metric grease nipples.
- How is a drive grease fitting sized?
- By the drilled hole it is driven into: a 3/16″ drive fitting goes into a 3/16″ hole. It has no thread.
- What hex is a 1/8 NPT 45 degree grease fitting?
- A 1/8″ pipe thread 45° grease fitting has a 7/16″ hex (Alemite and Lincoln agree).
- How do you measure a grease fitting?
- Thread size, the hex across the flats, the angle between head and thread (straight, 45°, 65°, 90°) and the overall height from the tip of the head to the end of the thread.