I'm sure eveyone is familiar with the Harbor Freight 93458 pneumatic rivet puller. I just preformed it's third rebuild.

The first is the one everyone should perform when buying anything from HF. Take it apart and clean out all the metal chips and shavings left over from manufacturing. Give the parts a visual inspection. It gives you a chance to familiarize yourself with how the thing works, too.

The second one will be when what you missed the first time bite you. For me there was a tiny burr inside the pulling head cylinder, It cut the O-ring and allowed the fluid to gradually leak out through the nose piece. I polished it out, replaced O-rings and got back to work with it.

My third time, came after another couple hundred rivets pulled. It started short stroking, to the point I had to pull the trigger 5 times to finish a rivet. This time the O-ring at the top of the pneumatic piston, where it drives fluid had worn out, allowing the fluid to blow out the exhaust port. I didn't use the HF replacement spare, but chose an O-ring with the same ID but fatter in cross section from an O-ring replacement kit. Topped up the fluids (I'm using a very light hydraulic bearing oil with a viscosity of 32).

I also found that the stems were starting to hang up inside. I moved the spring loaded griping head out a few hundredths of an inch. It is longer then the gauge length of the HF multi tool, but now everything is working.

We'll see how long this lasts.