Because of effloresence appearing on my porcelain tiled deck after rain events, I am planning to replace the existing grout with epoxy grout which will create a waterproof barrier. But I first need to remove the existing grout joints, which are < 1/8" width. It's my understanding that porcelain tiles can be susceptible to chipping so I'm not certain which method would be most appropriate to perform this work. I was considering using a grout blade on my oscillating tool, but I wanted to get some feedback before proceeding.
There is a Dremel Grout removal attachment, which consists of a fixture to hold the tool at a 45 degree angle, and you can get a 1/16 inch carbide cutter bit.
I've used this setup several times to remove grout for renewal or tile replacement. It can work quite well if the grout is really a sixteenth wide. Its not easy, but you can chip the tiles if you're not careful. I inevitably break the bit, and will always buy at least two.