When I was 12 years old, my father gave me a Ford straight
six-cylinder engine and told me to fix it. I really had no clue
what I was doing, but with his tutoring I stripped it down,
replaced its worn and broken parts, and put it back together.
After 100,000-plus miles, that engine is still going strong
under the hood of a '65 Falcon.
So the first time I explored the innards of a pneumatic roofing
stapler, I felt right at home: There was a piston, cylinder,
rings, intake, exhaust — it was basically a simple motor.
Since then, I've been responsible for maintaining and repairing
the 30 or so pneumatic tools in my company's arsenal, several
of which are themselves antiques. From brad nailers to framing
guns, most pneumatic tools are very similar, inside and
Regular maintenance, which takes only a few minutes, is an
important part of our daily routine. The better we take care of
our tools, the less frequently we have to open them up. And
when the time comes for a more thorough cleaning and parts
replacement, we can do the job on site or in our workshop in 30
minutes or less, which saves us travel time to the tool-repair
shop and downtime on the job.
It's important to keep the inside of your pneumatic tools clean
and lubricated. Cleanliness starts with your air hoses; if
they're handled carelessly, uncoupled quick disconnects can
fall on the ground. And if dirt and sawdust get in a hose
fitting, they'll contaminate your tool the next time you plug
it in. Sand and dust quickly wear out the rubber O-rings inside
— or, even worse, they can scratch the metal cylinder.
Once this happens, power diminishes rapidly.
An easy way to prevent debris from entering hoses is to keep
the male and female ends of each hose connected, disengaging
them only when you're ready to make a connection to another
hose or a tool. Protect a tool's male fittings with plastic end
caps. The inexpensive ones designed to cover the cut ends of
wire shelving fit pretty well (see Figure 1).
prevent moisture and debris from getting into pneumatic tools,
keep hoses connected to each other when not in use and protect
tool fittings with plastic end caps.
Internal lubrication keeps air tools running smoothly. I have
never had good luck with automatic in-line oilers that are
connected to the discharge of the compressor. They may work
fine on shop compressors, but they don't work as well on mobile
compressors, because they tend to snap off and leave the inside
of hoses oily. A daily lubrication ritual is just as
When I take tools out in the morning, I drip six to 10 drops of
lubricant into the air intake (if the manufacturer has a
different recommendation, I'll follow that), using only
lubricants formulated for pneumatic tools. Don't use motor oil
as a lubricant, because it can deteriorate O-rings and bumpers.
On days when I'm driving lots of fasteners, such as during
sheathing operations, I'll usually relubricate at lunchtime
Figure 2.Nailers should
be oiled on a daily basis with lubricants designed specifically
for pneumatic tools.
Moisture diminishes the effectiveness of lubricants and can
accelerate corrosion of the metal parts inside tools. To help
keep moisture out of your pneumatics, drain any water from the
compressors daily, and cover the tools in the rain.
Each time you take a tool out to use, look it over carefully
for loose or missing screws and parts. Check that the contact
tip mechanism is free and not gummed up, and oil it lightly
after every couple of uses.
After plugging in the tool, listen for air leaks. Leaks around
gaskets may indicate loose screws or a damaged gasket, while
leaks around the trigger may signal a malfunction that can
compromise safety. Leaks from the exhaust port or the nose of
the tool may be a symptom of worn O-rings inside.
With the tool connected, look for cracks or small holes in the
housing. Cracks usually are caused by dropping the tool, but
small holes can develop on old tools worn from rough use.
Cracks and holes are serious — a cracked housing can
explode and send fragments flying — and can't be
repaired. If you find a crack or a hole, take the tool out of
service but save it for parts (Figure 3).
Figure 3.An air tool
with a cracked body is potentially dangerous because it can
blow apart. It should be removed from service.
Periodically, pneumatic tools need to be disassembled and
cleaned, and their worn parts replaced. According to at least
one manufacturer's guide, this is a chore that should be done
on a weekly basis, but I doubt this ever happens in the real
world. My framing nailers are used every day, and I disassemble
them every one to two months. I open up my finish nailers once
a year, but they get used only four days each month. I
overlooked a siding stapler for five years until the piston
started sticking, but I don't recommend waiting until that
Check the manual first. Before opening up a tool's motor, it's
a good idea to make an assessment of what parts will need
replacement and round them up ahead of time. I start with the
owner's manual; most have exploded drawings of the tool. That
the piston O-ring will need to be replaced is a given. Most
other O-rings are stationary and will need replacement only if
you damage them while disassembling or reassembling the
Though made of hardened steel, the business end of a driver can
still show signs of wear. You can check the condition of the
driver before disassembling the tool by dry-firing it. First,
empty out the fasteners. Hold back the contact safety nose
while aiming the tool away from you (and others), and then
squeeze and hold the trigger (Figure 4). The tool will fire and
the end of the driver will stick out the nose. Worn drivers
will have rounded or chipped edges that can lead to jams or
Figure 4.To check a
nailer's driver without disassembling the tool, dry-fire it
(with fasteners removed) while keeping the trigger
The bumper also may need replacement, but most of the new ones
are more durable than those used 10 or 15 years ago. I wait
until after I've opened up the tool to run out — if
necessary — and pick up a new bumper from my local tool
shop. Its service department stocks such common replacement
parts as O-rings, bumpers, gaskets, and drivers for most
nailers and staplers. Other parts that don't break often, like
cylinders, nail magazines, and caps, will likely involve
special orders. Some manufacturers bundle parts into "rebuild
kits" that include several O-rings and perhaps a driver. But if
the only part your tool needs is a piston O-ring, these kits
aren't very cost-effective.
Some disassembly required. I work on a large, clean piece of
cardboard that gives me space to spread out parts; when I'm
done I can throw the mess away. With the diagram nearby for
reference, I start taking the tool apart by removing the cap
screws. Some tools have spring-valve assemblies under
compression beneath the cap, so I back the screws out evenly to
avoid jamming (Figure 5).
Figure 5.After carefully
removing the cap screws (left), the author takes off the cap to
expose the cylinder and piston inside (below). Working on a
large piece of clean cardboard makes it easy to keep track of
parts and to clean up afterward.
Sometimes the cylinder and piston are beneath metal or plastic
disks that snap into place, but usually the cap is all that
needs to be removed to see these parts. When there's a nut on
top of the piston, I use a pair of needle-nose pliers to grip
it and pull the piston out (Figure 6). If the top of the piston
is flat, I insert a thin metal rod up the nose to push the
driver and piston out.
Figure 6.Some pistons
have a nut on the top that can be grasped with a pair of
needle-nose pliers, making it easier to pull the piston out of
Because air flows between the cylinder and the body, a lot of
dirt collects there. So, for a complete cleaning, I remove the
cylinder in addition to the piston. Cylinders are held in place
with two or three O-rings between the base or sides of the
cylinder and the body of the tool, and they snap in tightly;
getting them in and out takes some effort.