Removing Stuck Grub Screws by Bill Fitzgerald
I have had considerable success using this method to remove grub screws that are stuck fast in threaded brassware. I presume that this problem occurs to others and it not just my lack of skill in removing them by mechanical means. Anyhow, soak the brass part in hydrochloric acid or spirits of salts. It is commonly used to remove mortar stains from new brickwork and is available from hardware stores or suppliers of building materials. About 24 hours seems to be needed after which time the steel grubscrew will have dissolved enough to be pushed out. My experience is that the brass is little affected and there is no apparent discolouration.
Needless to say, this technique is unsuitable if there are any steel components in the part.
Bill Fitzgerald. Copied from spanner.