In my assembly, how can I scale one of the components and cut paste it ("C" casting)?
We can't open the assembly without the Part files.
SolidWorks has a Scale tool. I don't believe I've ever used it, but you can probably use it to scale your Part, then create a separate configuration so the Scale feature is suppressed in your first configuration. Then insert it into your assembly and choose the new configuration for the second instance of the Part. All this about configurations is assuming that you don't want to scale both instances.
If I understand you correctly, you want to have one version of the part at the current size, and another version of the part that is scaled? I'd suggest making a second configuration in the part that has a Scale feature added, and have the Scale feature suppressed in the default configuration. Then in the assembly you can have some instances of the component in each configuration.
I want to scale the tray part to the "C" casting, then cut & paste the casting for the other side of the tray.
To scale the tray you'll need to open the tray part file and add a Scale feature (Insert > Features > Scale). There you can set the scale value.
To make a copy of the C casting, you can simply hold ctrl, click on the casting in the graphics area, and drag off to the side and another instance of the casting should appear. You can also hold ctrl and click on the part name in the tree and drag over into the graphics area.
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