dismanteling tools with the table and applying fire clay on it will make it pristine.

[Lancemaker]

steps on recreating the bug :

1 - get a very used tool
2 - take off the head on a crafting table
3 - apply fire clay on it
4 - check the durability, it will be like a new one.
5 - mount it back.

Conclusion, applying fireclay to tools makes them pristine. also its quencheable.