I need to put glass shelves in a frameless 42" upper dish cabinet but I am nervous about their weight-bearing capacity. What thickness of glass would you recommend and is support at only the two ends sufficient?
From contributor A:
That would depend on how wide the case is and what will be put on it. You should plan for the worst possible scenario with the weight.
Their chart demonstrated how the weight bearing capacity decreases as the span widens. (i.e., a 12-inch wide shelf at 1/2" thick can bear 345 pounds, the same shelf at 2' wide can bear 81 pounds and a 3' span can only bear 33 pounds). These measurements are for annealed glass only supported at the two far ends. Your example, being 42" wide, means that you're probably at the (pardon the pun) break-even point. A 3/8" piece of glass that long will look nice and light but will likely only be able to bear a maximum of 3-5 pounds of weight.
I'd figure out how to get a center support in there somewhere, or build a wood or metal picture framework and use that to buttress the glass. Your 42" is an awful long area to trust to just glass.