We have received some antique cutlery-most is one piece metal which we can kosher. The knives are two piece but, if done professionally, the blades can be removed and replaced. We have been given two scenarios as to procedure. One says-take the blades out, then hagala for everything, replace the blades and then tevila [alternative tevila and then replace the blades]. The second opinion we received was, no need to remove the blades-soak the whole object in a caustic poison, or spray with a strong roach spray or something equally nasty. This renders anything as lo achilat kelev. Then proceed as before. I would like an opinion and also some sources to understand where the two approaches come form.
For Toiveling: Handles do not have to be detached and you can toivel them with the handle. (Responsa of Maharam Rothenberg 3;184, Shulcham Aruch YD 202;4, Aruch Hashulchan ibid 7 and more.) For Kashering: clean cutlery only needs Hagala and if the set you have is such – there's nothing more than that to do. The only issue is, if it's not clean - how to clean the knives. If it can be perfectly cleaned without removing there's no need to do so what so ever, if not - first prize will be to remove the blades; if difficult it's equally kosher to soak in caustic poison or burn the grime so there's nothing really left. (Shulchan Aruch OC 451;3, ibid YD 121;7, Mishnah Brura on both sources, Hagalat Kelim 6;4, ) in any event I will recommend you to go over the process of Hagala with a competent rabbi since there's more to it than what you and I wrote.