Is your excavator bucket still rattling and pounding out your pin bosses? If your pins and bushings have been run loose too long they can end up enlarging the pin boss on the backside of the bushing. This means no matter how many times you try to replace the bushing it will always be sloppy and have play in it. 

This will leave you with several options for the repair. 1) You can replace the whole piece, usually this is not even an option. 2) You can cut the boss off of the machine and have a new one made to the correct spec and then weld it back on. Usually this is fairly time consuming and involves more work than necessary. 3) You have it line bored! 

What is line boring? Line boring is a multi step process to bring your pin boss back to its original spec to properly hold a bushing. The first step is to setup the jig on your machine, then an initial cut pass is made to bring the assembly back to round. After the jig is trued up and the first cut is made then it is time to make some weld passes on the boss. Now if this isn't badly out of shape then then next and final step would be to cut the bore to the proper size. If the unit needs a lot of build up it is done in several steps of weld & bore to achieve the correct size.