Probably, but they'll come around. Could I get fired? Sure, but I'll deal with that when the time comes. But, until that time comes, I'll have to carry a large chest back and forth I guess. That'll make it easier to avoid such conflicts that you mention. Thanks again.
Bottom line, if you take tools home with you that you don't already own, to make money "on the side" in your profession, you're stealing from the person who you work for who actually owns the tools.
People wonder why some larger business can be more expensive than smaller businesses, and one reason is the right tool for the right job costs money. That money has to come from somewhere.
If he asks I'll be up front with him.
Sorry, but if you can't be up front with him (your boss) from the get go, you know you're doing something wrong.
Sometimes competing on the side with your boss can be very dangerous.
From my expereince, if you're competing with your boss in your profession or trade, it's not "can be very dangerous" but "is very dangerous".
Make sure you have a backup plan.
Other than being in the unemployment line.
My suggestion is to be honest and upfront with your boss. What do you honestly think your boss is going to say?
Not sure about the auto mechanic industry, but my trade is a pretty "small world" and sooner or later, someone will find out what you're doing if you're trying to keep it a secret and don't want anyone to know what you're doing other than potential customers.
You mentioned that you lived 40 miles away from the shop where you currently work. Unless this guy (or you) does wonders with anything that comes into the shop at the absolute lowest price "around", how much business do you think you can "take" from him due to the drive time? I just don't see people in your boss's "business territory" driving out to see you for you to do work unless you tell them you do side work.