To add to the “greatest website of all time” aspect, they provide STEP files of a ton of those parts (maybe all of them?). When you’re drawing up a project like the OP’s in CAD, you can import the STEP file of the parts from McMaster and verify fit right there. If you’re using Fusion 360, there’s a button right in the app to browse McMaster and download the model!
And... if you need a part with a particular shape but not necessarily the strength of metal... shhhh... you can just 3D print it yourself from the STEP file.
And... if you need a part with a particular shape but not necessarily the strength of metal... shhhh... you can just 3D print it yourself from the STEP file.