Pat it would help to see what part you are talking about as I'm not sure either. You can post a picture from your own hard drive by using the Advanced post option and then going below the dialog box and clicking Manage Attachments. Maximize the screen you go to to see all the buttons that will need to be clicked.
Ryobi made the router for Sears so good chance the threads are metric but it was made specifically for Sears so it's possible Sears specified SAE hardware. I've never bothered checking the old one I have to see. I wouldn't put too much into it as there are no parts available anywhere. Especially collets.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.