Tuning Up a Pneumatic Nailer - Continued

The new biodegradable degreasers used in the automotive industry work great for cleaning the gunk off pneumatic tools. I fill one spray bottle with full-strength degreaser and another with fresh water for rinsing. To contain the fluids, I work over a large plastic tub while spraying the inside and outside of the tool with degreaser. The degreaser can burn skin, so I wear plastic gloves as a precaution. I wear eye protection, too.

The inside of the tool usually cleans with just a spray and rinse, but tools that haven't been cleaned regularly require a little elbow grease to remove thick gunk. The outside often has caked-on grease that also needs scrubbing to remove. I save old toothbrushes for just this purpose. After a couple of sprays, some brushing, and a rinse, the tools look like new (Figure 7).

Figure 7.A biodegradable automotive degreaser is an effective cleaner, and can be sprayed on both the exterior and interior of the tool (top left). Most tools can simply be rinsed with water afterward (top right). A toothbrush is perfect for removing stubborn dirt (above left). Two cylinders — one clean and one dirty — demonstrate the importance of regular cleaning (above right).

Inspect and replace as necessary. The bumper sits at the bottom of the cylinder. Made of rubber or plastic, it stops the downward motion of the driver piston. When bumpers become worn, the driver may overdrive fasteners or may not return to the top of the cylinder. A bumper needs replacing only when it hardens and starts to chip. To see if it's still resilient, I poke it with a screwdriver. For closer inspection and possible replacement, I use long needle-nose pliers to grab and pull out suspect bumpers. When a bumper hasn't been replaced in a while, I go ahead and put on a new one when I replace a worn driver. That way, I ensure I won't have to do a major overhaul for a while.

Replacing the driver is the only operation where I find it necessary to be in a shop equipped with a bench-mounted vise. Drivers are connected to pistons in several ways: They can be threaded, bolted, or pinned. To disconnect the two parts, I clamp the driver (or extended portion of a piston) in the vise. When I'm reinstalling either a threaded driver or a bolt-on driver, I coat the threads with thread-locking compound. This keeps the driver or nut from accidentally unscrewing during use (Figure 8).

Figure 8.

The author uses a thread-locking compound when reassembling a piston and its threaded or bolt-on driver.

Before putting the nailer back together, I visually check the lining of the cylinder for deep scratches. Tiny scratches aren't a problem, but deep ones can cause O-rings to wear quickly. The only times I've had deep scratches on a cylinder were when a driver broke inside and jammed the piston. On those tools, I replaced the cylinder, piston, and driver all at once. I've never had success honing out deep scratches.

Touching Up the Tip of a Driver My coil roofing nailer was long overdue for an overhaul, and I noticed that the end of the driver was rounding over. But I balked at the $120 price for a new driver, figuring I could buy a new nailer for under $300. So I decided to try grinding the face of the old driver to give it a few more years of life before replacing it. The easiest way to touch up the face of a driver is on a grinding wheel. But since I don't have one, I put a fine belt in my belt sander instead and clamped the sander in a vise. When I put the face of the driver against the belt, I didn't try to take out all the imperfections; that would wear off too much metal. Just a few light presses against the sander were enough to flatten the face sufficiently. Limiting the grind time to 10 seconds and dipping the driver tip into cold water prevented the steel from losing its temper. The driver on my 15- to 16-gauge finish nailer wears quickly. So even though it costs only $10 to replace, I'll occasionally touch up the tip without even taking the tool apart. First, I remove the nails and connect the air. Then, holding back the contact trip nose, I fire the tool and keep the trigger depressed. This exposes enough of the driver tip that I can give it a quick touch-up grind on my belt sander. Instead of being smooth and flat, this driver tip is chipped and worn (inset), causing jams and unset fasteners. To touch it up, the author clamps a belt sander in a vise (a grinding wheel could also be used) and lightly sands the tip with a fine-grit belt until the driver is flat again.

Fitting the Pieces Back Together

Before reassembling the tool, I wipe the inside dry with paper towels or a clean cloth, then spread a thin film of pneumatic lubricating oil inside the cylinder with my finger. (Spray oils are usually too thin and can attack and deteriorate the O-rings.) I pop the new piston O-ring into its groove dry, and then coat it with oil. The trick to reinserting the piston into the cylinder is aligning the driver with its slot or hole. You can't see either the hole or the driver once you place the piston over the cylinder, so it usually takes five or 10 minutes of fumbling before the driver pops into place. To prevent the top edge of the cylinder from gouging the new O-ring, I carefully ease the O-ring into place by working my fingers around it as I press down on the piston. Finally, I push the piston all the way down to the base to make sure it moves freely, then drip five more drops of oil on top before closing up the tool (Figure 9).

Figure 9.Before inserting the piston into the cylinder, the author spreads a thin coat of lubricant on the interior of the cylinder and on the piston's new O-ring (top). After aligning the driver with its slot inside the piston (bottom), he eases the piston back into the cylinder, taking care not to damage the O-ring.

Before mating the cap back on top, I check the gasket or rubber ring. Gaskets can usually be reused, but sometimes they'll stick to both halves of the tool during disassembly and need to be replaced. In that case, I use a fresh razor blade to scrape off the old gasket material. Rather than running back to the repair shop when a gasket tears, I keep a sheet of thin gasket material (available at automotive-parts stores) in my shop and cut a new one. If the old gasket is relatively intact, I use it as a template. If not, I apply a thin coat of oil to the tool's cap and press it onto the gasket material, marking the inside and outside edges of the cap. This makes it easy to trim the new gasket to size.

If the cap is spring-loaded, I'm careful to torque down the screws evenly. And I make sure that the cap seats down evenly to the cylinder as I bring the two together.

Before test-firing the tool, I make one last overall inspection. I check all screws to make sure they're tight, operate the contact trip nose to see that the spring and the trigger mechanism are moving freely, and check that the magazine is functioning properly. Sometimes when I put things back together, I misalign something and parts jam. A good look-over usually catches any problems.

Since air flows through the trigger valve, I deposit a little oil inside it during the regular daily oiling process. But when trigger valves start leaking air, they need replacing. This is a procedure that I hand off to my repair shop.

Also, coil nailers have a second, much smaller piston system that advances the nails into the firing chamber. I don't find that this mechanism needs regular servicing, but I do check and oil it during the final inspection. First, I remove any nails and open the loading door to get a clear view of the advancing pawls, and then I connect the air and dry-fire the tool. The pawls should move back and forth easily during the firing cycle. Next, I drip oil onto the piston connecting the rod and the pawls (this is also part of my daily oiling routine).

When I do notice a problem with the advancing system, I drop the tool off for service. There are far too many tiny parts and springs in this system, and I would rather let someone else mess with them.

Mike Guertin is a builder and remodeler in East Greenwich, R.I., and a member of the JLC Live construction demonstration team.