Object modifiers can only be applied to objects. Therefore when you merge two objects, most modifiers will not work as intended. You'll need to apply the bevel before merging.

HellJumper の投稿を引用：

Object modifiers can only be applied to objects. Therefore when you merge two objects, most modifiers will not work as intended. You'll need to apply the bevel before merging.

Thanks Helljumper (love the tutorial videos you do), but that's what I think I did. The item I am creating is made up into several objects. On most (if not all of them) I used bevel to make it look nice, but when I tried merging some of them, they looked all rough, like the bevel went away.

Have you added hard edges to your model? Once you merge everything, add an edgesplit modifier to the entire object and then mark sharp edges so that the entire object isn't one big smoothing group.

HellJumper の投稿を引用：

Have you added hard edges to your model? Once you merge everything, add an edgesplit modifier to the entire object and then mark sharp edges so that the entire object isn't one big smoothing group.

I figured out what was wrong. I didn't hit apply after setting the modifier.