So I have an impact driver (uses hex bit attachments) and would like to know if anyone has found any bits that go directly to sizes to say 21mm. I've broken too many of the 1/2 socket adapters and Home Depot is on to me now.

I have been using these but they snap at the thin part.

 

When you buy bits they need to be for impact tool's even Phillips head tips has to be for an impact or they just break

 

I have two battery powered impact drivers. The one that takes the adapters like in your picture isn't strong enough to brake anything socket relater. It's more for driving screws, the impact effect giving it a little more power than a regular drill/driver.

What brand and model driver are you using?

 

while those small impact drivers are handy 21 mm is to big for that sizeof driver, you should be looking at least a 1/2" drive.

 

I have one of the drivers you speak of but I also have a Makita cordless impact wrench works great worth the money. Never let me down.

 

I would also recommend getting a bigger impact for bolts that size.
That being said, I have used the dewalt impact (1/4" hex to 1/2" square drive) many times and have yet to break one.

 

Just break torque with standard wrenches and then hit it with what u got. Don't expect to break/set torque with that. But it can make quick work of unthreading bolts!!!

 

My philosophy, too.
I never use an impact to set or break torque; only to run fasteners off, or on after starting by hand.

 

I agree with the others here, you will end up breaking more adapters or burning up the motor before you either accept that it won't be breaking or setting fasteners or buy an impact wrench and use it for what it was designed for....I also use my impact driver to make running the threads a little quicker and easier

 

There are multiple 1/2" cordless guns under 300 that will do everything you need.

A 1/4" inch lbs. gun with a half inch shank adapter is not the right tool for the job.