In the Northeast there are many equipment dealers that sell hydraulic hammer but very few know how to rebuild them. When you rebuild two hammers a year you don't gain very much knowledge. Currently there are a couple companies in the Northeast that all they do is rebuild hydraulic hammers. Large quarries from around the country send them large hydraulic hammers to rebuild. They have invested a large amount of money in equipment like test stands to do the rebuilds. At any time they can have 15-20 hammers being rebuilt in their facility.
If you need any help with a hammer rebuild let me know.