I have run into this problem a few times. It all depends on how a plate is made. Some have a shallow rim that doesn’t clear the screw head. Some plates are completely flat on the bottom. So here’s the solution. When this happens, I just drill the second plate as well and insert a longer screw/bolt. OR use a spacer in between.
The perfect spacer plate is a smaller, shallow plate turned upside-down so the rise in the plate covers over the screw head. Then I use silicone to affix the next plate or dish to the spacer. Make sure the spacer plate is smaller in diameter so as not to really show and minimize the degree of space in between. Sometimes this technique presents a kind of 3-D effect to the art piece. It helps if the spacer plate doesn’t detract from your colors. Sometimes a clear plate accomplishes this beautifully. I always keep an eye out for good spacer plates when I’m out shopping for dishes.

Go with a 20. It’ll get the job done faster. I personally use a 12v only b/c it was lighter weight and fit my small hand comfortably. I use my drill a lot, so comfortable fit was important to me. But it does take longer to drill my holes. A 20v will cost more than a 12v, but you’ll appreciate the voltage for other uses, as well. Have fun with your project, I’m always available to answer any further questions!

Thanks for your feedback. I try to write the best, most helpful articles, so it’s nice to know I’m hitting the target! Congrats on drilling! I’d be more concerned with harsh weather, a rock flying from a snow blower, or getting hit by a plow truck etc. Yes, you certainly can seal around the joints where dishes come together. You can even apply a thin layer around the inside of the hole using a toothpick. I typically recommend bringing the flower heads indoors over the winter (they detach from the post so the post can be left in place). However, I did experiment and leave some plates out during our cold, snowy winter in AK. They were ceramic plates and didn’t break. That’s not to say they can’t break! Most regular dinner plates are sealed; they can take the microwave or oven or freezer (as can most glass). I just haven’t left my stuff outdoors enough in winter to be able to advise. What I would do is two test pieces. One with the silicone and one without and see what happens. I did leave a teacup garden stake out one winter. The cup filled with rain water and froze. With a few freeze/thaw cycles, the ice eventually cracked the tea cup…but I will say it lasted a long time until that happened.

Some plates cannot be drilled b/c they cannot withstand the pressure. So a more delicate or ornate plate—one with thinner glass will break. ‘Correlle’ is a brand that cannot be drilled. I had to learn this myself! So only drill a thicker, heavier glass or ceramic plate. But you could use the more ornate plate as the middle plate in a dish flower which I glue. (I only drill the rear plate) Also…if you are just learning to drill, get yourself a few “practice” plates…ordinary ceramic plates to experiment with until you get the hang of it.

In my research, I have not seen makers use them. The plate does not spin…it’s stationary sculpture. So, while someone could use a grommet, a hole larger than 1/4″ would probably be necessary. (I don’t know how small grommets come). In my experience, 1/4″ diameter hole is sufficient. Interesting idea, though.