I recently had cause to "save" a bunch of collets that came with my Rivett lathe, at first glance they looked a bit beyond it and if it hadnt been for the fact that they were made by Rivett I might not have troubled, but in truth I am glad I did, as first impressions are not always the best ones.
I just thought it might benifit someone else with a similar situation if I documented how I went about it. First I cleaned out all the usual muck from the slots and blew them through with an air line, then I took them to a wire wheel, I know that sounds a bit excessive, but in this case there really wasnt an alternative, anyway this kind of steel is so hard that it was quite a safe operation and in no way did it scuff the steel, it removed the surface rust leaving the collet dirty and revealing any pits. From there I then went through them again this time on a polishing bob with a little fine polishing soap, this was just enough to remove the gunge from the first operation and revealed just how good or bad each one was. In point of fact I believe that they are all usable and this quite surprised me when I remember how they looked before.
The thing to bear in mind here is that you now have a clean collet with a few pock marks, and provided that there is still a high proportion of the original surface still in tact there should not be a problem.
I then took a stick of fairly course mahogany stuck it in the lathe and turned it to fit the main bore of the collets from behind, this enabled me to stick each one in turn on it and with a small amount of metal polish remove the last traces of the polishing soap and give them each a shine up. After this they all needed cleaning again as the polish gets into the slots.
So far so good, but now came the inside, especially the gripping surface, these were all more tarnished than rusty with the exception of perhaps three or four of the bigger ones. What ever I did here I didnt want to damage or reduce the material, so how to do it. What I went for in the end was to turn down the mahogany to suit the largest and slip it on whilst the lathe was running, then turn it down for the next one repeating the process right down to the size of a match stick and I can say it worked extremly well. They all came up as new with out the need for any abrasive or polish.
I think it was a wothwhile project, although I wont deny it took quite a while to do it, but as they say the proof of the pudding is in the eating so take a look at the before and after shots for yourself.