A Guide to Grease Guns and Grease Nipples

Lubrication is essential to maximise the safety, efficiency and functionality of any type of machinery with moving parts. But how can you properly lubricate those hard to reach areas? 

In this guide from The Hosemaster, we’ll explain what grease guns are and how they can help you care for, and operate, your machinery. Keep reading to learn more…

What is a grease gun?

But first, what exactly is a grease gun?

In short, a grease gun is a tool used to apply grease to different types of machinery joints and bearings.

Grease guns use a pressurised system to force lubricant through a grease nipple that’s attached to the joint in question (see more below). This is much easier, and cleaner, than other methods of lubricating the area.

They’re usually used when manual application of the lubricant would be difficult to do without completely disassembling the mechanisms involved - which can be highly impractical.

That’s why grease guns are an essential piece of equipment to ensure your machinery is functioning efficiently. Applying a lubricant reduces friction between moving parts, which helps to prevent premature wear and tear within your systems and extend its lifespan. 

It also reduces heat building up, ensuring your machinery is safer to use for prolonged periods of time.

Grease gun terminology

In the diagram below, we’ve labelled the most important parts of a grease gun for your reference. We’ve also explained what the different parts do, so you can understand how a grease gun works.

Coupler: this is where the grease gun directly connects with the grease nipple, so it’s important to ensure it’s kept clean and clear to avoid blockages.

Extension pipe: this extension pipe connects the coupler with the body of the grease gun, and can also be called a fixed tube.This design makes it easier for the grease gun to fit in small gaps and connect with hard-to-reach areas. 

Extension hose: the additional hose extends the reach of the grease gun, and offers more flexibility when necessary.

Grease gun head: the grease gun head holds the primary mechanisms, and is where the barrel is screwed into.

Handle/Pump lever: this provides the power for this type of grease gun. In this case, pushing the lever pumps the grease through the hose and out the coupler.

Barrel: also known as the grease tube, this is where the grease is stored. The grease is normally stored in a pre-filled cartridge, or directly in the barrel.

End cap: the end cap is used during filling when you need to lock the plunger rod in place.

Plunger rod handle: the plunger rod, or follower rod, is what puts pressure on the grease within the barrel. This is spring-loaded, and moves when the lever/trigger is pumped.

Whilst not highlighted, many grease guns come with an air release valve to help air escape before use.

Note: the majority of these parts are universal across different models of grease gun. However, the pump lever may look different depending on how the grease gun is powered.

Where would you use a grease gun?

Grease guns are primarily used by mechanics and engineers, but they can be a valuable investment for hobbyists looking to maintain their machinery.

They’re often used on larger machines that have several moving parts that need lubrication, where it can be difficult to apply grease under normal circumstances, like:

• Agricultural machinery and equipment.
• Vehicle maintenance, in garages or at home.
• Gardening and landscaping tools.

What is a grease nipple?

Also known as grease zerks or fittings, grease nipples are a type of fitting attached to bearings or other mechanisms that need internal lubrication. 

For example, they’re commonly seen on suspension rigs where it’s otherwise impossible to manually apply lubricants to the internal systems.

Within a grease nipple, there is a small ball bearing on a spring, which is compressed when lubricant is pushed through via a grease gun. This acts as a valve to allow grease through, without allowing it to double-back or leak out.

Alongside making it easier to lubricate machine elements, grease nipples and guns are a cleaner and more efficient lubricant delivery method.

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Types of grease nipple

Grease nipples can come in several different designs depending on the needs of your machinery. The simplest have a straight design, and can be attached wherever there is a need.

Alternatively, angled grease nipples can make tighter or awkward gaps more accessible, which combined with a flexible extension hose means you should be able to attach the coupler of your grease gun firmly.

Where it could be dangerous to have an external fitting, some grease nipples are designed to sit flush to the surface. These usually require a cone-shaped grease gun coupler, as they’re installed differently.

Button head grease nipples are flatter, and allow for a higher volume of lubricant to pass through. This is ideal for more heavy-duty applications where you need to supply a large amount of grease quickly.

Types of grease gun

The overall construction of a grease gun is largely the same, whichever model you choose. However, the design does change depending on the power type of the grease gun. In this section, we’ve highlighted the four main types of grease gun, and how these can be used.

Pneumatic grease guns

Pneumatic grease guns use air to put pressure on the grease and force it out though the coupler. 

Instead of a lever or pressure grip, pneumatic grease guns use a trigger to work. This means they’re easier to use over an extended period of time, or if you have decreased grip strength.

However, the air needs to come from somewhere. Pneumatic grease guns have to be attached to a source via cord, which can limit their range of use.

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Pistol grip grease guns

A pistol grip grease gun works by compressing the handle to force the liquid out.

This is a popular design because they’re smaller than other levers, and you can use them one-handed. However, this can get tiring if used over long periods of time, so this type of grease gun is better for routine maintenance or short bursts of activity.

One benefit of the design however is that you can use this tool with more dexterity because they’re cordless, and reasonably light. This makes it perfect for close quarter use, like when you’re underneath a car.

Side lever grease guns

As you’ve seen in the diagram above, some grease guns use a side lever, which is raised and compressed to put pressure on the grease.

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These are the most efficient manual grease guns in terms of volume per stroke, which is ideal for when you need to move a larger supply of lubricant at once.

However, the downside is that these require two hands to operate, which limits where and when you can use them.

Battery-powered grease guns

Battery-powered grease guns are ideal for those who want an easier power system than a pump lever, as they’re trigger operated. This means you can use them one-handed.

However, unlike pneumatic grease guns, the battery pack ensures these models are cordless, offering you more flexibility in where you want to work.

The main drawback is that you’ll need to remember to charge the battery pack regularly to avoid it dying mid-task, unlike manual units where the only limit is how much grease they have - and how tired your hand is.

How to load a grease gun

Before you can use your grease gun, you need to know how to load it properly. This ensures the grease will be released smoothly, and prevent blockages as much as possible.

Grease guns can be loaded in a few ways. The most common way is to buy a pre-filled grease cartridge that can be inserted into the barrel. This is easy, and much cleaner than the alternatives.

Below are some step-by-step instructions for how to load a grease gun with a new grease cartridge.

1. Loosen the barrel from the grease gun head to break the vacuum.
2. Pull back the plunger rod and lock into place.
3. Unscrew the barrel to separate it from the head.
4. Remove the empty cartridge (if necessary).
5. Prepare your grease cartridge by removing the plastic cap at the bottom, and pulling the metal tab on the top to remove the lid.
6. Wipe the excess grease from the tab as you remove it, then put the metal into the plastic cap for easy disposal.
7. Slot the cartridge into the barrel. The cartridge should rest on the top of the tube.
8. Screw the barrel and head back together.
9. Purge any air that may be between the grease cartridge and the gun head (see more below).
10. Release the plunger rod.
11. Pump the mechanism to push grease through the system.

Top tip - on step 8, make sure you don’t release the plunger before you’ve screwed the barrel in.

Alternatively, you may wish to bulk load your grease gun directly from a larger store of grease. In this case, one option is to do the following.

1. Remove the head from the barrel.
2. Insert the opening into the grease.
3. Pull back on the plunger handle to fill the barrel.
4. Lock the plunger rod into place once the barrel is full.
5. Clean off the excess grease before reattaching the grease gun head.
6. Purge any air from the top, if necessary.

Top top - if you feel a break in the suction, stop and start over. This prevents air pockets from becoming a problem during later use.

You can also fill your grease gun by hand, but this is much messier. This would follow a similar process to pressure loading, but you would instead scoop grease into the barrel by hand.

The issue with both of these methods is that there’s a higher risk of introducing dirt and contaminants into your grease mixture because the bulk container is open.

Instead, many use a specific fitting to bulk load their grease guns. This has a lever and nipple to connect from the grease drum to your grease gun, filling the barrel directly without needing to remove the lid of the drum.

How to purge air from a grease gun

Air pockets are inconvenient and can cause an inconsistent flow of grease during operation. With that in mind, it’s always a good idea to ensure your grease gun is free from unwanted air. 

To bleed air from your grease gun, try some or all of the following steps.

1. Once you’ve loaded your grease gun, loosen the barrel from the head slightly to allow excess air to escape. Pump until grease comes out, and then re-tighten.
2. Push down or unscrew the air release valve. These are increasingly common, and are an easy way for air trapped between the grease gun head and filling to escape.
3. Pull out the follower rod and twist until it locks into place with the metal plate inside. Then you can put the rod handle on a flat surface and push down, whilst the air release valve is open. This puts pressure through the grease to force any air pockets out. Then, release the follower rod back into the grease gun.
   

How to store a grease gun

It’s important to store your grease gun appropriately, as this can help extend the lifespan and ensure your grease gun is safe for use. 

Storing your grease gun horizontally helps to protect the plunger and spring from persistent stress and premature wear. This also means that if the grease does start to split, it does so evenly through the gun and is easier to fix by shaking the tool before use.

You should also keep your grease gun in a cool, dry room, away from direct sunlight. Excess water and heat can cause your grease to oxidise, which is a waste of money and resources.

Can you leave grease in a grease gun?

In short, yes, you can leave grease in a grease gun. 

This is because a grease gun is a sealed system, which should keep contaminants and dirt away from the lubricant.

However, you should be aware that grease will inevitably split over time. This is because the oil and thickeners in the mixture have different densities, so tend to separate if left still.

Top tip - even though you can leave grease in your grease gun, you should make sure you’re cleaning it regularly. This prevents blockages, and will make your life easier when it comes to using your grease gun.

How to use a grease gun

Once it’s been loaded, using a grease gun is actually very simple.

All you need to do is attach the coupler to the grease nipple, and pump the handle (or press the trigger) to release the grease. Then, you just disconnect the coupler and move onto the next fitting.

The amount of grease you need to use varies depending on the size of the joint you’re looking to lubricate, and how frequently you apply the grease.

For example, if you grease the area often, you won’t need to use as much grease every time. As a general guide, if you notice grease leaking from the joint then it’s overfilled. This isn’t necessarily a problem, but it does waste grease and cost you money in the long term.

We’ve put together some of our top tips for how to use your grease gun.

• Clean your grease gun coupler and grease nipple thoroughly before use to prevent any contamination.
• Ensure your grease gun coupler is securely attached to the grease nipple before pumping the handle. This ensures you’re not wasting any lubricant and it’s actually being applied.
• Consider using auto-locking couplers. These are easy to use, and help prevent the coupler from coming loose midway through the job.
• If the grease isn’t flowing into the grease nipple, it’s likely because there is a blockage. Don’t try to force more lubricant through - you should always either replace the fitting or clear the blockage before use.
  

Find grease guns and accessories at The Hosemaster

Our excellent range of high-quality, but affordable, grease guns, grease nipples, and other accessories are perfect for applying lubricants to machinery and equipment whatever the job.

Browse our range today, or get in touch with our friendly team of experts to get more advice and detailed product information. 

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