On a current model (2005) Shimano 105 Rear Derailleur: I opened up my rear derailleur plate to better access my chain for a thorough cleaning. When I am reassembling the tension pulley, I noticed that when tightening the pulley bolt, it can be so tight that the pulley itself does not spin freely. But I had to tighten it that much in order to get it as tight as it felt when I uncrewed it. Am I missing something? Am I supposed to use some loctite on the pulley bolt threads so it stays in place without having to be torqued down so much that it restricts the spin of the pulley? Thanks in advance for the assistance...I did a search but couldn't find advice on something this specific and I am a newbie at repairs and maintenance.

See: https://www.parktool.com/repair/readhowto.asp?id=76

The article mentions the installation torque as 30 in-lb (not much), and recommends a thread locking compound. Originally, the screw probably had a thread locking compound on it so you had to exert quite a bit of torque to break it free and the residue on the threads offered some resistance as you removed it.

Note, there are various grades of thread locking compounding. For bicycle component, the "serviceable" (such as Loctite #242 blue) type is sufficient. Serviceable means you can remove the fasterner at a later time with a little effort. Some compounds are more permanent and may require the use of heat to remove - not good for bikes.

In general, the Park site is a good resource for wrenching.

Welcome to the world of wrenching!

You didn't mix the pulleys up did you? The one for the center and the one for the bottom are different. I bet this is your problem. I have the exact same derailluer and had mine apart last weekend to grease the pulleys. If they are installed right you can tighten them up with no problems. You will notice when you take them back apart that they are stamped with different names on their sides.

Tightening the bolt should never sieze the pulley. Make sure the bushing is in there. It's the little cylinder shown in this pic from Park Tool's link above:

Thanks a bunch for all the tips. mechBgon was right on - the little cylinder had fallen to the floor and I had not noticed it. Luckily I found it, cleaned it up, and I am back in business. Also used the Loctite 242 on the bolts. Everything feels good and I have already been out for a test ride; all shifting was awesome. Nothing like clean parts - so nice and shiny!!!!! Thanks again folks!