Another way to do this is to talk to the boss and instead of telling him all sorts of things ask for his advice. Ask him how he would like you to handle this. Let him now you are more than willing to handle this but you want to make sure you do it correctly. This puts him in a strange position, an employee has acknowledged him as the "wise boss", so his ego gets a little stroked and now he has to show you how to handle this situation. It is now his duty to step up and be the shop manager and handle his people and show you he is in control. Let him know that you can not stand for the situation as it is now but you don't want to affect shop productivity with a bunch of drama. Ask him how you should handle this.
My guess is 2 things will happen. One, the problem will be handled by the boss and two, the boss is going to look at you as a team player and he is going to find a reason to promote you sooner than scheduled (if your work is good) because you handled the situation without bringing unnecessary drama to the shop.
Of course he could tell you to shut up and get back to work! Who knows!
Uncle Joe you sound like a very wise man. I bet you have a few years experience under your belt.

Everybody gets what they want with minimum drama.
As far as loaning tools, I don't mind doing it , but I'm very straightforward about my tool rules. If you break it, no big deal, just be sure and let me know. I like to know where my tools are, so ask before you borrow. Other employees can borrow tools, but you better not be borrowing my tool to loan to a customer. Ratchets, screwdrivers, etc are NOT hammers. Only hammers are hammers. So far, in 25 years of turning wrenches, have only had a couple newbies that couldn't follow the rules.
I used to work with a mechanic named Mark, who had a way of helping people remember to bring back borrowed tools. If Mark had to go looking for a tool that was borrowed, he would take something from that person and hide it. It might be car keys, cell phone, a commonly used tool, or whatever. He'd just let that person go through the whole day, wracking their brain wondering where they could have left the "lost" item

. Then, around quitting time Mark would kindly inform that person where he could find whatevever it is he was looking for and proceded to give them a lecture about returning borrowed tools in a timely manner.
Taught 'em a lesson plus had a little entertainment whatching 'em look for their stuff. Hehe
