Just wrapping up my porcelain tile install on my 32x60 shower. I am installing framed sliding shower doors and was researching ahead for that. There are 3 screws installed in each vertical side. The screws provided are 1/8"x1 1/2". The instructions say to use the anchors provided, however when framing out for my shower, I installed studs right where these are going to go. What's the best way to go about doing this and are these screws sufficient? Obviously I won't be anchoring with the studs. 1 1/2" will barely make it through the track, tile, and Hardiebacker. I'm assuming these are meant to be used due to the anchors, so I should look for something longer? Also, I suppose I should predrill 3/8" holes through the ceramic with a diamond bit, huh?
What you were provided with is the standard install hardware for shower doors. Most people don't know exactly where the studs are. You can definitely install the doors as recommended using the provided screws and anchors. Since you know where the studs are, you can use the longer screws but do not drill 3/8" holes, way too big. stick with the diameter of the screws provided, you don't want to have to drill the tracks with larger holes
The weight of the doors is on the tub, and it's hard to find studs behind tile. That's why studs are not normally used for shower doors. However, since you know where the studs are, the benefit of using longer screws is that you can get away with drilling much smaller holes. Go for it. Drill just barely large enough for your screw through the tile and board, and then switch to a smaller pilot drill for the joist. Use screws that won't rust with heads that will not rip through the door frame.