The 1/16 inch NPT grease fitting is the smallest taper pipe thread size in the NPT family, at 27 TPI on a 1:16 taper. It serves small hydraulic components, instrument housings, and European-built machinery with NPT ports. A 1/4″-28 UNF straight-thread port takes a different fitting; the systems do not interchange. For 1/8 inch NPT, see the 1/8 inch NPT grease fitting; for metric threads, the DIN 71412 grease nipple family.
Thread Specification and Identification
The thread runs 27 TPI on a 1:16 taper, a 3/4 inch diameter change per foot. Minimum engagement is 4 full threads; drive with an 8 mm (5/16 inch) hex. The OD is 0.3125 inches, against 0.405 inches on 1/8 NPT. NPT and BSP threads do not interchange; a BSP port needs a BSP grease nipple. The taper wedges flanks metal to metal, needing no gasket, and holds against vibration.
Head Styles and Clearance
Pick straight for clear axial access; 90 degrees when an adjacent part blocks the front; 45 degrees for partial blockage; and the button head where the lowest profile avoids snagging near rotating parts. See the grease fitting types guide for head-style basics.
| Head Style | Overall Length | Head Diameter | Minimum Clearance |
|---|---|---|---|
| Straight | 0.50″ | 0.25″ | 1.5″ |
| 90 degree | 0.65″ | 0.28″ | 1.2″ |
| 45 degree | 0.60″ | 0.27″ | 1.3″ |
| Button | 0.45″ | 0.31″ | 1.0″ |
Tolerance is +/-0.02 inch on length and +/-0.01 inch on head diameter.
Materials and Working Pressure
Three body materials are offered at different working pressures. Service temperature runs from -40°C to +204°C continuous, peaking at +232°C for up to 30 minutes. A spring-loaded ball check with a 440C stainless ball at HRC 58 opens under gun pressure and reseats when the gun comes off.
| Material | Working Pressure |
|---|---|
| Carbon steel, zinc plated | 3,000 PSI (207 bar) |
| 316 stainless steel | 3,500 PSI (241 bar) |
| Brass | 2,000 PSI (138 bar) |
Installing a 1/16 NPT Grease Fitting
- Clean the port with a thread chaser to remove old sealant, rust, and chips.
- Wrap 2 – 3 turns of PTFE tape clockwise, keeping it off the first thread so no debris enters the grease path.
- Tighten by hand plus 2 – 3 turns on the 8 mm hex to 10 – 15 ft-lb (13.5 – 20.3 Nm), never past 15 ft-lb; soft aluminum and cast iron housings crack or strip.
- Plan angled head orientation before final tightening: backing off breaks the taper seal, so a wrong angle means removal, new tape, and reinstall.
- Run one gun stroke: grease should flow freely, and none should seep at the threads.
Grease Compatibility
The ball check passes mineral and synthetic greases in NLGI grades 0 – 3; match grade to duty below.
| NLGI Grade | Typical Use | Temperature Range |
|---|---|---|
| 0 – 1 | High-speed bearings, centralized systems | -40°F to +250°F |
| 2 | General purpose | -20°F to +350°F |
| 3 | Heavy load, low speed | 0°F to +400°F |
When to Replace a 1/16 NPT Grease Fitting
Replace when the ball check stops resetting, grease seeps past a clean installation, the body or hex cracks, or the threads are damaged. A clogged fitting is usually replaced whole; the small passage is hard to clear.
Where This Size Fits and Where It Does Not
- Not interchangeable with 1/4-28 UNF straight threads.
- Working pressures are fitting ratings; confirm system pressure when ordering.
- A small fitting for compact grease points, not high-flow distribution lines.
- Angled head orientation must be set before the final torque pass.
To confirm thread, head style, and material, get a quote for your 1/16 NPT fittings.
Frequently Asked Questions
How is 1/16 NPT different from 1/4-28 UNF?
NPT is a taper pipe thread sealing metal to metal as the flanks wedge under torque; 1/4-28 UNF is a straight thread sealing at the port face with a gasket or O-ring. They do not interchange.
How do I tell 1/16 NPT from 1/8 NPT?
Measure the thread OD: 0.3125 inches versus 0.405 inches; both run 27 TPI, so diameter is the check; the 1/8 inch size is on the page linked above.
When should I choose 1/16 NPT?
When the port is already cut 1/16 NPT, as on small hydraulic parts, instrument housings, and some European machinery; when the housing is too compact for a 1/4-28 UNF body; or when replacing an existing part.
Does 1/16 NPT need PTFE tape?
Yes: 2 – 3 turns clockwise, kept off the first thread so no debris enters the grease path; metric DIN 71412 fittings go in dry instead.
What torque should I use?
10 – 15 ft-lb (13.5 – 20.3 Nm), hand-tight plus 2 – 3 turns on the 8 mm hex, never past 15 ft-lb; aluminum and cast iron crack or strip easily.
Can I back off an angled fitting?
No. Backing off breaks the taper seal; remove the fitting, apply new tape, and reinstall to the correct orientation.
Which material should I pick?
Zinc plated steel covers 3,000 PSI (207 bar), 316 stainless 3,500 PSI (241 bar) for corrosive or washdown exposure, and brass 2,000 PSI (138 bar) where a softer thread is preferred.
Which grease grades work?
Mineral and synthetic greases in NLGI grades 0 – 3 pass the ball check; match grade to temperature above.
What if the fitting clogs?
Stop when the gun feels abnormally hard, then remove and inspect; the small passage is hard to clear, so clogging usually means replacement.
Who supplies this fitting?
IsoHiTech Lubrication Systems is a lubrication equipment supplier founded in 2023, engineering since 2006. Send port thread, head style, and material requirements to inquiry@isohitech.com or contact our sales team for a quote.
