The Locking Grease Coupler is a lock-on end for a grease gun hose or rigid extension. Four spring-loaded jaws clamp onto the fitting head mechanically, so the operator keeps both hands free at line pressures up to 12,000 PSI (827 bar).
Lock-On vs Standard Push-On Couplers
A standard push-on coupler stays on the fitting only through friction and constant hand pressure. It attaches fast, but at higher line pressure it can be pushed off the head.
This locking coupler divides the work differently: press the thumb lever to retract the jaws, slide the head over the fitting, and release the lever so the jaw spring clamps on. The coupler then holds itself in place and keeps grease directed into the fitting for better spill control. To disconnect, press the lever and pull straight back; never bend the coupler sideways.
Key Specifications
| Specification | Value |
|---|---|
| Working pressure | 12,000 PSI (827 bar) |
| Gun-side thread | 1/8″ NPT male |
| Jaw mechanism | 4-jaw, spring-loaded, thumb lever release |
| Fitting head sizes | 6 mm, 8 mm, 10 mm, 1/4″-28 UNF, straight and angled |
| Body material | 420 stainless steel, phosphate coating |
| Jaw material | Heat-treated 4140 alloy steel, HRC 45 – 50 |
| Overall length | 4.2 in (107 mm) |
| Weight | 5.2 oz (147 g) |
| Flow rate | 150 – 200 g/min at 1,000 PSI |
| Radial clearance needed | approx 25 mm |
| Seal options | NBR (installed), FKM, EPDM; all replaceable |
Seal Options: NBR, FKM, or EPDM
The coupler ships with an NBR seal installed. NBR covers -40°C to +93°C (-40°F to +200°F) and suits petroleum-based greases NLGI 000 – 3. The FKM option is rated -23°C to +204°C for synthetic oils and chemical media. The EPDM option is for water-based fluids; for machinery in washdown or hygienic areas, confirm the EPDM option when ordering. All three seals are replaceable.
Fitment, Thread, and Clearance
The gun-side connection is a 1/8″ NPT male thread that fits most manual, pneumatic, and battery grease guns. Install it hand-tight plus 1/4 turn; confirm the thread form and sealing arrangement when ordering.
The head needs approx 25 mm of radial clearance for the jaws to open. The body is 420 stainless steel with a phosphate coating, and the jaws are heat-treated 4140 alloy steel at HRC 45 – 50. The coupler is rebuildable with replacement seals and a jaw spring.
What Is Supplied
Each order includes the locking coupler assembly with the NBR seal preinstalled and an instruction card. FKM and EPDM seals and jaw springs are ordered separately.
Honest Limitations
- The jaws grip the outside of a standard fitting head, so the coupler cannot hold concave or flush-type fittings; for recessed fittings see our concave grease nipples and plan for a needle or adapter-style end.
- The head needs approx 25 mm of radial clearance; tightly shrouded fittings may not give the jaws room.
- It fits common 6, 8, 10 mm and 1/4″-28 heads – confirm damaged or non-standard heads before use.
- The seal is a wear item; a coupler that weeps grease at the fitting usually needs a new seal, not a new coupler.
Not sure a locking coupler suits your grease points? Send us your fitting details for a quick check.
Frequently Asked Questions
Should I choose a locking coupler or a standard push-on coupler?
Choose the locking coupler when you grease at higher line pressure, want a free hand, or service fittings you cannot hold steady; a push-on coupler suits quick, low-pressure jobs on easy-access fittings.
Will this coupler fit my grease gun?
It has a 1/8″ NPT male thread and fits most manual, pneumatic, and battery grease guns. Confirm the thread form and sealing arrangement when ordering.
What is the maximum working pressure?
The coupler is rated up to 12,000 PSI (827 bar). Flow is 150 – 200 g/min at 1,000 PSI, suiting hand and air-operated guns.
How do I release the coupler while the line is still under pressure?
Press the thumb lever to retract the jaws, then pull straight back off the head; do not bend sideways. The jaws need approx 25 mm of radial space to open.
Can I use it on concave or flush-type grease fittings?
No. The four jaws grip the outside of a standard fitting head and cannot latch onto recessed heads. For those fittings, see our concave grease nipples range.
Which fitting head sizes can the jaws grip?
The jaws grip 6, 8, and 10 mm heads plus 1/4″-28 UNF heads, on straight and angled fittings such as our DIN 71412 grease nipples; for corrosion-prone equipment, pair with stainless steel grease nipples. Confirm damaged or non-standard heads before use.
Which seal should I order: NBR, FKM, or EPDM?
NBR covers petroleum-based greases NLGI 000 – 3 from -40°C to +93°C. FKM runs -23°C to +204°C for synthetic oils and chemical media. EPDM is for water-based fluids and washdown or hygienic machinery.
Why is grease escaping around the fitting head?
Usually one of three causes: jaws not fully seated, a burr or damage on the fitting head, or a worn seal. Reseat the coupler, inspect the head, and replace the seal if it still weeps.
How long will the coupler last?
There is no fixed service life; wear depends on pressure, lubricant, and attachment frequency. Seals and the jaw spring are replaceable, so ask us about rebuild parts when performance drops.
Who supplies this coupler and how do I order?
IsoHiTech Lubrication Systems supplies this coupler; the team was founded in 2023, engineering since 2006. Send your fitting sizes, grease type, and gun model to inquiry@isohitech.com for a quotation.
