Slip gauge question.

I concur with Howard .

Iron oxide (rust) is very hard and an abrasive in itself (rouge) so more damage can be done to the slip gauge if removal is done mechanically. So use phosphoric acid or another mild acid to soften the rust and scrub with a tooth brush. When hardened steel, and I believe slip gauges are, become rusty the rust may form along weakness lines in the crystal lattice so appears as strands or small pockets. Once the rust is softened with the acid and scrubbed check, under a microscope, to see if the rust has gone and if not gently use a pointed stylus to pick it out. Better to use several short acid/scrub sessions than leaving them in the acid too long. Also make sure you dry the gauges after each acid/scrub/rinse session as a film of rust can quickly form. Be sure to clean the slip gauges in isopropyl alcohol or another degreasing fluid as the rust may have formed under the layer of protective oil the gauges should have on them. The oil can soak into the rust making the action of the acid less effective. Cleaning the gauges in a ultrasonic tank may also help liberate stubborn rust but check this on the worst affect gauge before doing it to the rest.

All said and done slip gauges are essential for the Gods of Precision but not so much for us mortals of imprecision.

Clive

Thanks all!

Up to now, I've given them a quick wipe over with a soft cloth and coated them with acf50 until I've got the time (and patience!) to sort them properly!

Even if they won’t wring together they are useful for checking the width of slots for most standard keyways, etc. The error on any couple of blocks used together will be minimal in those situations. You may have noted that one of the responders has multiple sets, ranging from ‘chip tray’ quality to tool room grades. I doubt he is the only one on the forum with more than one set.