When it comes to chrome most manufacturers make their sockets as thin as they dare to withstand the force necessary to apply required torque for the size of fastener the socket may encounter. Cheap brands made of inferior alloys and hardening procedures will be thicker than the known brands. if you need thinner the lathe is the way to go but chucking it in a drill and running it against a file will work too. Steel will fail at a fault or stress riser in it's composition. In this case that is the deepest scratch the file made on the surface. If you need to apply heavy force with a thinned down tool you should smooth the surface with fine emery cloth to remove all scratch marks (stress risers). This is why a lathe is superior, it is concentric, not always what you achieve when hand filing. For carbs hand grinding should be fine.
Here's a shot of a socket that has been turned on a lathe and then polished to remove stress risers. It's next to another thin walled snap-on socket but it's now about 3/8 the thickness at the very tip and tapers to about 5/8 of the thickness 1/2 way up at the end of the broaching. It still withstands torquing 35 ft lbs.
I am just looking for a regular thinwall socket (5/16") or a set of thinwalls. I need a thinwall to take apart the needle seats on a snowmobile carb. 
