powertoolstools
I have a Hitachi NR90AC5 framing nailer that still functions correctly, but some air leaks from around the trigger. Sometimes, after firing a few nails, it doesn't leak air anymore. Then later after more nails are fired, it goes back to leaking again. The performance of the gun is unaffected, but I'm concerned something may be wearing out.
It hasn't been used that heavily and I oil it every day.
What part needs replaced to make it stop occasionally leaking from the trigger?
As others have said, a framing hammer is a specialty claw hammer.
So what makes it different? First, weight. A framing hammer is typically 20-32 oz, compared with 10-16 oz for a "normal" household claw hammer. That helps it pound large nails in only a few blows. Related to that is the much longer handle on a framing hammer.
Second is the face of the head: it's waffled to prevent slipping off the nail head, helping prevent bent nails. A regular claw hammer will sometimes have a textured face but not nearly as pronounced, and the face may also be smooth. A regular claw hammer often also has a domed face to allow a skilled hand to sink a nail below the surface with minimal surface damage: that's a feature you won't see on a framing hammer.
Third, the claw is straight since it is optimized for prying boards apart. A regular claw hammer is optimized for pulling nails.
If you're only building a garage, I'd recommend using your regular hammer rather than buying a framing hammer. (Or best of all, just go rent a nail gun!). For inexperienced carpenters, the time spent hammering will probably not be what slows you down. Also, the framing hammer is tiring enough that after a couple hours you may actually be faster with a smaller, regular claw hammer.
If you do get a framing hammer I recommend a lighter one. You'll work faster when you use it, you won't lose much power over a heavier hammer, and you'll feel much better on the second day. In 2010 if you hammer enough that a 32oz hammer makes a difference versus a 24oz hammer, you have a nail gun anyhow.
Gauge is the thickness of the drive tangs on the saw chain. Chain gauge must match the groove width on the bar.
The only effect chain gauge will have on standard spur sprockets is the contact area it presents on the spur teeth, thicker gauge = wider contact area.
Rim Sprockets use a pocket that must be wide enough to allow the drive tangs to seat.
Pitch is the length of the links that make up the chain, basically the distance spanned by three rivets divided by 2 and chain pitch must match the sprocket pitch so the chain is properly driven.
The reason for measuring over the span of three rivets and taking the average to calculate pitch is that the drive link has the rivets closer together than the tooth and span links.
Where the pitch matters, as shown on the simpler spur sprocket chain drive mechanism on an electric pole saw. Chain drive tangs must be the right distance apart to engage the sprocket teeth properly.
This leaves the remaining variable which is the number of links. More links, longer chain which must of course be accommodated by having a longer bar. Since the chain is seven links longer (81-74), the chain will be about 2.3" longer. If the bar nose radius on the new bar is equal to that of the old bar, your new bar should be about 1" longer.
Also, there are different geometries on saw bars that can be used to take up that extra length which only can be seen by comparing the old bar against the new bar.
Best Answer
I have repaired all the internal parts for the trigger assembly multiple times. Works for a while then begins to leak again. Adding grease to the o rings helps but it’s just a junk trigger assembly.