The M4 x 0.7 grease nipple is the smallest common metric thread size for hydraulic-type grease nipples, built for precision instruments, small assemblies, and compact machine parts; this page covers dimensions, materials, torque, and mounting. If your port is M5 x 0.8, see the M5 grease nipple; larger threads sit on the M6 grease nipple page. The DIN 71412 grease nipple overview covers the full size range.
Specifications and Dimensions
Confirm the thread against your port before choosing materials or heads.
| Parameter | Specification |
|---|---|
| Thread | M4 x 0.7 metric fine |
| Wrench size (hex across flats) | 7 mm |
| Overall length, straight Form A | 14 – 16 mm |
| Thread engagement | 5 – 6 mm |
| Head diameter | 6.0 – 6.5 mm |
| Ball diameter | 2.5 – 3.0 mm |
| Bore diameter | 1.5 – 2.0 mm |
| Injection pressure compatibility | up to 400 bar |
| Installation torque, zinc-plated steel / stainless steel | 3 – 5 Nm |
| Installation torque, brass | 2 – 4 Nm |
How the Fitting Works
A spring-loaded ball check seals the head: coupler pressure opens it, and the spring closes it when the coupler pulls off, keeping dirt out of the grease path.
Materials and Temperature Limits
Zinc-plated carbon steel uses free-cutting steel 1.0718 (11SMnPb30+C); the head is case-hardened to 550 HV minimum and the body sits at 60 – 85 HRB, under clear or yellow chromate passivation, rated -40°C to +120°C. Stainless 304 (1.4301) and 316 (1.4401 / 1.4404) rate 85 – 95 HRB, -40°C to +200°C with the standard spring. Brass CuZn39Pb3 (CW614N) rates 55 – 75 HRB across -50°C to +200°C, and stainless 316 and brass give the widest chemical compatibility.
Choosing a Configuration
Form A is straight at 14 – 16 mm for axial access; Form B comes at 45° or 90° within +/- 2° with 1.5 mm minimum wall at the bend, and the 90° form adds 5 – 10% pressure drop. A DIN 3404 button head swaps the ball for a flat head, flows 2 – 4 x more, and needs its own coupler. See the grease fitting types guide and the grease line fittings range; a flush head 0 – 2 mm proud belongs to DIN 3405 on the concave and flush-type page.
Mounting Procedure
Clean the port, remove burrs or old sealant, and confirm the pitch with a thread gauge; metric and inch series cannot be mixed. Start by hand for 2 – 3 turns, then torque per the table. Skip PTFE tape or anaerobic sealant: metric threads seal at the flanks, and fragments can foul the bore or jam the ball check. Inject one gun stroke, confirm the ball check seats, and check the flank for seepage.
Replacement Signals and Honest Limitations
The M4 x 0.7 fitting serves small cavities and tight access; a main bearing supply line is beyond a 1.5 – 2.0 mm bore, so step up to M5 or M6 there. The 90° variant adds roughly 5 – 10% pressure drop, which long runs or cold grease can expose. Confirm the coupler type and wrench clearance at order stage; if unsure, tell us about your fitting application. Replace the nipple when grease seeps from the head after the gun pulls off, when the thread is damaged or slips, when the head cracks or deforms, or when it loosens at correct torque. In corrosive environments, inspect for coating breakdown, pitting, and discoloration.
Frequently Asked Questions
How do I tell M4 x 0.7 from M5 x 0.8 and M6 x 1?
Use a thread gauge: M4 x 0.7, M5 x 0.8, and M6 x 1 are not interchangeable, and M4 is the smallest common metric size; larger threads sit on the M5 and M6 pages.
Which head form do I pick: straight, 45°, 90°, or button?
Match head form to access space: straight Form A for axial access, 45° or 90° Form B for angled access, button head for high-volume points.
Why will a standard hydraulic coupler not fit a button head?
A DIN 3404 button head is a 10 mm flat head that only a dedicated button-head coupler grips, not a standard one. These rate up to 1,034 bar (15,000 PSI).
What wrench size and torque does an M4 nipple need?
The hex is 7 mm; torque to 3 – 5 Nm in steel or stainless and 2 – 4 Nm in the more fragile brass.
What injection pressure can an M4 grease nipple take?
DIN 71412 sizes cover injection pressure up to 400 bar; the M4 x 0.7 is no exception.
When is zinc-plated steel not enough?
Zinc-plated steel suits dry indoor service to +120°C; choose 304 or 316 stainless for washdown or chloride-rich settings, or brass down to -50°C.
Should I wrap the thread in PTFE tape or add sealant?
No: metric threads seal at the flanks, and sealant fragments can jam the ball check or foul the grease line.
Which grease grades work with an M4 nipple?
NLGI #0 through NLGI #3 greases on lithium, calcium, or complex-soap thickeners, mineral or synthetic base oil; NLGI #2 is the most common.
When should I replace the nipple?
Replace it when grease seeps from the head after the gun pulls off, when the thread slips or the head cracks, or when it keeps loosening under torque.
Who supplies the M4 x 0.7 grease nipple series?
IsoHiTech Lubrication Systems is a lubrication equipment supplier founded in 2023, engineering since 2006. For M4 nipples or selection help, request a quote through our contact form or write to inquiry@isohitech.com.
