My HF rivet gun has been requiring 3 or 4 triggers pulls to set a rivet. When I tried to rivet left rib 9 to the the right wing, it would not work at all. I noticed a loose part in the pulled mandrel collector, so I took the rear part of the rivet gun apart. The loose part was a small tube that is held by friction to the oil piston.
I finally realized how the gun functions:
- when the trigger is pulled, compressed air flows into air cylinder, forcing it to move upward - the air piston stem is forced into the oil filled cylinder in the frame - the stem acts like a piston and forces the oil up into the oil cylinder in the top of the frame - the oil forces the oil piston rearward - The oil piston pulls the jaws rearward - As the jaws move rearward, they clamp around the mandrel, setting the rivet
The obvious problem with riveter was that the oil had leaked out of the oil cylinder, so the air piston stem was pushing on air instead of oil, and thus did not move oil piston very far. This problem is mentioned in the manual. I don't know why I have been ignoring it.
I reprimed the gun and then it appeared to set rivets with a single pull. I probably need to reprime it every time I use it.
I will try storing it horizontally to slow down the oil leak.
I put in a new o-ring (1.25" x 1.125" x 0.0625") to replace p/n 10-A which was missing. Perhaps that will reduce the oil leakage between uses.
