What Mechanical Grease Cups Are
A mechanical grease cup is a small unpowered reservoir that screws directly onto a bearing housing or lubrication point and feeds grease by simple mechanics. No power supply and no compressed air are involved: a screw-down cup is advanced by hand, and a spring-loaded cup is driven by its own internal spring. Both families suit points a worker can see and stay engaged with.
Screw-down cups hold a charge of grease under a hand cap, and each turn of the cap pushes a controlled quantity toward the point. Spring-loaded cups hold a larger charge that the spring presses toward the point as a small steady feed. A third family, the ball-type cup, works on a different principle and has its own page.
The stated capacity of any cup is the grease volume it holds, not the dose per turn or per day. On screw-down models the dose depends on how far and how often the cap is advanced; on spring models it depends on grease stiffness and temperature.
Screw-Down and Spring-Loaded Capacities
The table states the declared envelope for both families. Anything outside it needs confirmation before ordering.
| Specification | Screw-down cups | Spring-loaded cups |
|---|---|---|
| Capacity | 1/4 to 4 oz (10-120 ml), by model | 2 to 18 oz (60-530 ml), by model |
| Feed principle | operator advances the cap by hand for a controlled quantity per turn | spring keeps a small steady feed on the point |
| Spring discharge pressure | not applicable | 2-65 psi (0.14-4.5 bar) |
| Operating temperature | -20°C to +120°C | -20°C to +120°C |
| Grease grades | NLGI 0 to 3 | NLGI 0 to 3 |
Spring discharge pressure is the gentle push the spring applies to the grease charge, not a system working pressure. A transparent body lets the operator watch the charge level without opening the cup.
Choosing Between the Two Types
The choice turns on one question: can a worker reach the point and stay involved with it? A screw-down cup suits points a worker can reach and inspect, because dosing is deliberate: the operator decides when to advance the cap and how far. A spring-loaded cup suits bearings that want a continuous trace of grease and spots that are inconvenient to re-visit often, because the spring keeps feeding between refills.
Neither family needs power or air, which is why cups persist on presses, conveyors, crushers, mixers, and farm machines. The trade is operator attention: a screw-down cup only feeds when someone turns it, and a spring-loaded cup feeds whether or not anyone is watching. The feeding rate of a spring cup also drifts with grease stiffness and temperature, so the same model moves soft grease faster than stiff grease.
Threads, Materials, and Filling
Mounting threads come in three forms. NPT is a tapered thread that wedges into a matching tapered port as it tightens. BSP is a parallel thread that seats against a flat face rather than wedging. Metric threads run from M6 to M16. Tapered and parallel forms are not interchangeable: forcing one into the other damages the port or leaves a gap, so confirm the exact thread on the machine when ordering. Metric-ported machines pair with the metric grease fittings range.
Bodies come in steel, brass, or cast iron, and transparent models are offered for watching the grease level at a glance. Filling happens in place on most models: open the filler, add grease of the same grade, and close it. Fillers and caps vary by model, so confirm the filler arrangement when ordering, and confirm seal compatibility with the fluid data sheet before ordering. The grease fitting types guide shows the common filler patterns.
If the thread form or filler pattern on the machine is unclear, send a photo of the installed point through the contact page before ordering.
Where Cups Stop Being the Right Tool
Cups earn their keep on points that are few, visible, and easy to reach. Once a machine carries many lubrication points, walking the line with cups stops making sense: a centralized lubrication system meters each point from one supply. The FAQ below covers when to make that move.
Temperature swings are the second limit. Both families are rated from -20°C to +120°C, but a spring cup’s feeding rate still drifts as grease stiffness changes with temperature, and stiff grades feed slowly in cold weather. For widely swinging temperatures, a different lubrication method serves better.
The third limit is vibration. Heavy vibration can back a screw cap off its threads, and it can disturb the settled feed of a spring cup. Machines under constant vibration are better served by a fixed lubrication method than by either cup family.
Checking Cups in Service
Condition checks replace schedules. Look at the grease level during rounds and refill when the charge runs low; transparent models show the level directly, while metal bodies are opened for a look. On screw-down cups, re-check cap tightness after exposure to heavy vibration, since screws can back off. On spring-loaded cups, watch for the feed trace at the point and confirm the cup still holds charge.
Refill with the same grease grade as the charge, and clean the filler area before opening so nothing enters the cup. Keep spare caps and fillers from the lubrication accessories page on hand for models that see frequent service.
Frequently Asked Questions
What is a mechanical grease cup?
A mechanical grease cup is an unpowered reservoir screwed onto a bearing point, feeding grease with no power or air supply. The operator or an internal spring pushes grease toward the point.
How do screw-down and spring-loaded cups differ?
A screw-down cup gives a deliberate, operator-controlled dose each time the cap is advanced by hand. A spring-loaded cup pushes a small continuous feed without attention between refills.
What capacity should I choose?
Screw-down cups hold 1/4 to 4 oz (10-120 ml); spring-loaded cups hold 2 to 18 oz (60-530 ml), by model. Capacity is the volume held, not the dose per turn or per day.
Which mounting thread do I need?
Cups are offered with NPT tapered threads, BSP parallel threads, or metric threads from M6 to M16. Tapered and parallel forms are not interchangeable, so confirm the exact thread when ordering.
Will a cup feed NLGI 2 or 3 grease in winter?
Stiff grades move slowly at best in cold weather, and the feed of a spring cup drifts with grease stiffness and temperature. Favor softer grades in winter; NLGI 0 is the softest grade these cups handle.
What happens under heavy vibration?
Heavy vibration can loosen screw caps, so re-check cap tightness as a condition check during inspections. For constant vibration, a different lubrication method serves better than either cup family.
Can a grease cup be refilled in place?
Most models refill in place, so the cup stays mounted on the point during a refill. Confirm the filler arrangement for the chosen model when ordering.
How does the ball-type cup compare?
The ball-type cup is the third sibling family, holding grease behind a spring-loaded ball check at the point. See the ball cup page for its working pattern and capacities.
When should I move to a centralized system?
When a machine carries many lubrication points or hard-to-reach spots, a centralized lubrication system feeds each point from one supply. Send the point count and layout through our contact page and we will size the route with you.
Who builds and supports these grease cups?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
