My combo square that I bought used on ebay, the rule was looking hazy or tarnished, and getting harder to read. I wanted to polish it, but didn't want to remove the black from the tickmarks or numbers. I used to work for Dremel and thus I have a bunch of little Scotchbrite buffs that they now sell. One is coarse(tan) and one is fine(gray). So I tried the gray on my rule and it worked great to remove the haze and brighten up the rule without hurting the ticks or numbers. I then pulled a mortice machine bit out that was all surface rusty and I used the coarser buff on that one. It took about 15 minutes, and one and a half buffs, but man did it polish up almost like new. Since it's a wheel on a shaft, it could get up in the spiral of the bit(1-7/16ths bit). Lo and behold, it's a Jennings bit. It came in the mortising machine I bought. I don't work there anymore, but those small buffs really work well for shining up tools like that. I finished by wiping some gun oil on the bit and rule (like I do with my chisels).