Doc Dan wrote:It may not be the tang of the knife. It might be in the pivot or between the scales and the tang. If you have a jeweler close by who has a sonic jewelry cleaner, see if you can put your knife into it for a bit. Once it comes out all the grime will be gone and you will need to immediately re-lubricate your knife. It should be smooth, then.
+1 on this suggestion, I'd add that if it's the Ti/Elmax version, have them blow it out with the gem steamer, until the whole knife is hot, that will not only blast out any remaining grit, but speed evaporation of residual cleaning solution. If it's an FRN model, light steaming is still fine, but I'd use only moderate heat on the plastic scales.
Another thing to remember about slipits is that the backspring has a notched depression that can hold grit in a spot that isn't easily seen or cleaned, at least not without disassembly. Working the blade through its range of motion while using external cleaning measures can often help clear that area.