Before everyone piles on with the insults and ridicule:
This method of "defretting" a bass by filing the frets down flush was a fad for a while. I think it was in the '80's. Some famous bassist did it to their Fender and then a bunch of people rushed to their tech and had it done to one of their Fenders. It was usually done with a big flat file, not by grinding. It was a quick, inexpensive way to convert a bass to fretless. It allowed you to try playing fretless, and it was reversible. It wasn't too expensive to convert back to fretted if you didn't like it.
These basses with the filed off frets weren't bad to play. You wouldn't get a pure fretless sound, because there was a slight clicking as you slid over the metal strips. But you could learn to play fretless on it while you saved up to buy a real fretless bass.
The problem was that, after a while, the tangs would start lifting up out of the slots. Then they were sharp as little razor blades. Particularly if the ends lifted up. You could cut yourself on them.
Un-de-fretting one of these necks wasn't really a problem....Once you figured out the trick of prying the tangs up with a little wedge from the end. Then it was about like a normal refretting job. Fix a few chips, resurface the fingerboard, put the new frets in. No permanent damage to the bass.
Remember that, 40 years ago, there wasn't this big flood of cheap import aftermarket necks or used necks that we have today. Getting a replacement neck for your Fender was pretty expensive. Like, nearly half the cost of a new bass.
This method of "defretting" a bass by filing the frets down flush was a fad for a while. I think it was in the '80's. Some famous bassist did it to their Fender and then a bunch of people rushed to their tech and had it done to one of their Fenders. It was usually done with a big flat file, not by grinding. It was a quick, inexpensive way to convert a bass to fretless. It allowed you to try playing fretless, and it was reversible. It wasn't too expensive to convert back to fretted if you didn't like it.
These basses with the filed off frets weren't bad to play. You wouldn't get a pure fretless sound, because there was a slight clicking as you slid over the metal strips. But you could learn to play fretless on it while you saved up to buy a real fretless bass.
The problem was that, after a while, the tangs would start lifting up out of the slots. Then they were sharp as little razor blades. Particularly if the ends lifted up. You could cut yourself on them.
Un-de-fretting one of these necks wasn't really a problem....Once you figured out the trick of prying the tangs up with a little wedge from the end. Then it was about like a normal refretting job. Fix a few chips, resurface the fingerboard, put the new frets in. No permanent damage to the bass.
Remember that, 40 years ago, there wasn't this big flood of cheap import aftermarket necks or used necks that we have today. Getting a replacement neck for your Fender was pretty expensive. Like, nearly half the cost of a new bass.