Yes. We install grab bars on porcelain tiled shower walls quite frequently. It has become much more common for us to encounter this situation. Porcelain tile comes in various durability grades, each one usually a little more difficult to drill through.
 Most experienced grab bar installers have developed their own techniques for working with porcelain tile.
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Regardless of the method used, drilling through porcelain is always more tedious and time-consuming and will quickly wear down any carbide or diamond drill bit.