I am trying to install a bath shower door . I need to drill holes into my tub and I am using a Milwaukee Drill with Dewalt titanium drill bit set. I am not sure what sort of bath tub mine is (fiber glass or metal) but I am having a hard time drilling 2 pilot holes. I held the drill for 20 secs and still nothing. Do I hold it for longer? What is the correct drill bit I use? Full View of bath tub

Pilot hole attempt

  • 2
    Now you've done it. Normally sliding shower doors hang from an upper track that spans and sits on the side rails which are anchored to the walls on either side. Since the lower rail really only serves as a splash guard and door guide it seems to me that it can easily be held in place by embedding it in a bead of silicon sealer. This removes any need to drill into the tub and keeps from disfiguring it should at some future time the door wants to be taken away.
    – Michael Karas
    Jun 16, 2016 at 3:28
  • Ok you have a metal or cast tub, it takes a bit more pressure and time if the drill bit is sharp. The goal is not to burn the bit (two fast) and to make progress with a small metal shaving (just right speed) . Give it some more pressure and time and you will punch through. Remember to seal the screws with RTV / rubber grommets so the rail is sealed.
    – Ed Beal
    Jun 16, 2016 at 4:23
  • Thanks for responses. I prefer to drill instead of just putting silicon sealer but if it becomes too hard I will just put the sealer. Jun 16, 2016 at 10:39
  • 2
    If the silicon sealer is used on clean oil free surfaces to place the lower rail that are about 60" long it is not going to "move around" at all once the silicon dries.
    – Michael Karas
    Jun 16, 2016 at 11:47

3 Answers 3


It looks like you're starting with a pretty large bit. I like to use the smallest bit I have (don't apply too much pressure, as skinny bits break easy) and work up. You're drilling more holes overall, but each one goes a lot quicker.


These are all good points. I'm going to provide some comments.

Your tub is made of an enamel coated steel. It's thin sheet steel so it's easy to work with, however it's not a ten second per hole job of fiber glass or acrylic. You should gauge down your bits (start with a small bit, and work to larger bits) until you hit the goal.

Also, don't use ice water, a room temperature, oil base lubricant is a better idea due to thermal dynamics and such (you can potentially have the bit violently explode, not fun). This can be cleaned up with dish detergent.

Lastly, your instructions should say to seal the screw holes and the bars with silicon (that is, before you put in the plug/screws you clean out the hole, and shoot a dab of silicon in to the holes, followed by applying it to the back of the framing parts before securing them to the wall/tub, again, cleaning the surface before applying). This avoids wicking and diffusion of moisture in to your surrounding structure (avoids mold from developing due to water infiltration).

  • I think my statement of using ice might have (rightly) miscontrued. I have used lubricants or ice... they work about the same. The ice is just a quick cool down for tub/bit. It isn't meant to "freeze" anything but can be used for 10 seconds to cool things down while you give your bit a rest.
    – DMoore
    Jun 16, 2016 at 20:03
  • I understood what you meant DMoore, I was hoping to avoid someone directly interpreting what you said, that's my reason for clarifying.
    – Chris
    Jun 24, 2016 at 4:23

Well titanium bits are OK for thin sheet metal but note that the titanium is just a coating on the bit. Once the coating is worn off they are really just your run of the mill cheap steel bits. Which is the situation you have here. The only reason your drilling is prolonged is because basically your bit is toast now. You are basically just rubbing the metal off, which is not good as this could make the hole slight wider than you have intended.

You really just need to buy a Cobalt bit. I would just get the size you need. Starting small and working your way up isn't something I have had too much success with for metal (although I would use this for tile or ceramic or stone). Your larger bits will catch on the hole that is already there and jam or possible drill off-center. You already have a decent size dimple in the one, so just use the right bit.

When drilling something this tedious I make sure that I am not applying too much pressure. About 20-30 pounds of pressure is enough - let the bit do the work. Also don't drill for more than 20-30 seconds at a time. The last thing is get a cup of ice. Lower the temperature of both the drill point and the bit itself in intervals will make the process faster and keep your bit working longer.

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