Question about Hitachi NR83A2 2" To 3 1/4" Full Head Framer with Depth of Drive
I need to repair the plunger rod malfunction in my framing nailer. It will drive a nail but the plunger does not retract .
This can be caused by any number of reasons.
If your piston driver does retract and slowly slides back to the downward position. This is a good indication that your piston o-ring is worn and needs replacing.
However the most common cause of the problem in which the driver will not retract at all, is that an o-ring has broken or has popped off of your piston cylinder. This o-ring is located in the bottom chamber of the gun.
Generally if the tool has not had the o-rings replaced in over a year, and if the tool is used quite often, it is good to have all the o-rings replaced especially when they are in contact with moving parts. Also as a rule, if you are unfamiliar with pneumatic tool repair, remove only the parts necessary to your problem. Often one problem can compound to many if you interfere with parts that are working properly.
To make a quick repair take following steps:
Disconnect the tool from air supply.
Remove the head cap from the body by removing the 4 bolts on the top. Be careful not to tear the gasket if you do not have a replacement.
With a thin tool pop the piston driver out of the top, by pushing upwards from the nose end.
If tool has dirt, excess oil, or grit inside clean it up as much as possible especially around rubber o-rings. Keep in mind that the tool needs oil to remain lubricated, don't leave tool dry around o-rings.
Use two head cap screws to gently remove the cylinder plate that is now exposed around the piston cylinder. Gently pull upwards (friction and an o-ring hold this tightly in place).
Now you can remove the piston cylinder. It may pop up because it is spring loaded, or it may be stuck downward. Carefully work it loose so it can be removed.
Examine the o-rings on the cylinder. Are any out of position? If there are any broken they must be replaced. If one popped out of position, reposition it.
The o-ring that can cause this problem is most likely the large rubber ring that covers a series of smaller holes that are positioned around middle portion of the cylinder.
Replace parts in the reverse manner of removal. Lubricate o-rings with appropriate assembly grease which is best, or pneumatic tool oil.
When the cylinder plate is reassembled, make sure that the cylinder is up. In other words, the spring that is surrounding the cylinder below the plate must be released as much as possible. This will enable flush contact between the cylinder and the parts on the head cap when the tool is assembled fully.
Replace the gasket, head cap, and the four bolts.
Hook tool up to air supply, check for air leaks, test fire tool.
Posted on Apr 18, 2009
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Posted on Jan 02, 2017
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