I have a PDF chart that shows all the torque parameters for hex bolt fasteners for all the different sizes. And obviously the bigger they get the more torque they can handle tested in lab conditions both dry & with lube. The problem IMO trying to buy large 1/2" sockets is that the torque properties of 40mm-50mm bolts exceed the capability of a 1/2" drive tools. I realise the OP is not necessarily trying to torque to maximum capability. For example max torque for a 24mm hex bolt is 445ftlbs (dry) so a 40mm would be massive! I think tool makers when warranting sockets have to think about these things more than we would think. Not having success loading PDF chart.
^^^^^ This.
It's about product liability. Manufacturers do not want liability for a tool (socket) that will invariably be used beyond design limits of the drive system it's put on. Even if you don't do it, someone, and more than just one, will do it, just because they can do it. Lawyers have a field day with stuff like this. ASME B107 is an industry standard that covers requirements for hand tools and accessories. B107.110-2012 covers socket wrenches and sockets. B107.300-2010 covers torque wrenches (the trailing four numbers are the year it was adopted). ASME is the American Society of Mechanical Engineers. When you buy a hand tool the manufacturer states complies with ASME B107, this is the standard they're using for design and test. These standards limit application of drive sizes. As an example, B107.300 for torque wrenches limits how much torque a given drive size can be designed to measure. The consideration is how much torque a socket put onto that wrench can withstand. I haven't gotten into B107.110-xxxx (for any year) and I'm not about to spend $100 for a copy (these docs are not free) but was able to find a free B107.300-2010. It's how I know there are limits by drive size on how much torque a torque wrench can be designed to measure, and be in compliance. I would not be the least bit surprised if there are limits on how large a socket can be made for a particular drive size, for impact and non-impact use, like B107.300-2010's limits on torque measurement for each drive size.
As others have mentioned, use a drive adapter to size a 3/4" down to 1/2" drive, but do so at your peril understanding the torque limitations of 1/2" drive compared to 3/4" and keep it within those limitations. A post in another thread bragged about putting 1200 ft-lb onto a SO 1/2" drive breaker bar without the breaker bar failing (IIRC "exploding" was the term used). Under ASME B107 that's well into 1" drive territory. Be aware that there is always someone around who will grab onto it and try to use it well beyond design or ASME standards limits, just because they can, and grouse about it to anyone who will listen when it breaks. Regarding the 1/2" breaker bar 1200 ft-lb event, the breaker bar and any 1/2" drive socket or other accessory that was used with it subjected to the same torque should be retired and destroyed or otherwise permanently disposed of. What you don't see on the outside are the molecular changes in the steel on the inside from the strain, which weakens the tool(s). It may appear visually to have suffered only elastic deformation (i.e. it goes back to original shape and condition) but internally at a molecular level (IMHO) there is without doubt plastic deformation (i.e. has new shape and condition). At some point later in its life, if stressed sufficiently again, even within ASME B107 limits, it may fail. IOW, it's a failure waiting to occur, like a land mine with a wonky fuse that might or might not work until triggered a number of times. It's one of the reasons I'm extremely loathe to loan tools to anyone, be they hard line hand tools or power tools, or electrical/electronic measuring instruments. If I do, it's under my supervision to prevent misuse and abuse. Too many do not respect tools they don't own. I see this routinely with monkey wrenches, especially older ones, with jaws no longer parallel and the back bent, from the obvious application of a cheater pipe. Just because the jaws could open 2 inches plus on a 10-12" monkey wrench, someone puts 800 ft-lb of torque on it to remove a 1-3/4" rusted nut and then moans about how the wrench is a pile of ****.
John
