Tricky spinning nut on bolt....

I'd carefully try a coupling nut with thread cutting oil on the stud instead of a die to straighten the threads-out. a nut will try to “move” material to reshape the threads and a die will “remove” material.
When testing the thread you should probably use a torque wrench and torque it to where a 6mm bolt should be (70-80 Ft Lbs) because it would be easy to over tighten a 6mm nut and strip the remaining area of the stud.

If the stud turns-out to be unsalvageable here are a couple choices.
1) Remove the stud, drill a tap drill size hole into the stud and tap it 6mm. The welded-in head of this stud is probably strong enough to hold a bolt.
2) . Drill a clearance hole where the stud is and you could probably weld-up some kind of a caged type of thing-nut and lower it into the big hole on the top of the box to catch a bolt inserted into the stud hole?
3) Additionally, because of that big hole in the top of that “Box” so it may not be a real high stress area you could get a piece of 6mm thick steel about 12mm x 30mm and tap a 6mm hole into one end and cut a hole in the top of that box and lower it to where the hole from the stud is and epoxy it into place on the inside of that box.

 

Forget using a die, you'll do more damage. If you want to repair threads ( probably unnecessary) the proper tool is a re-threader. The size there is M6x1.00. It looks like a 6mm nut and takes a 10mm wrench or socket. As I have recommended before, just put a few washers on and a new nut. It's really that simple.

 

Drill a hole slightly smaller than the tap, then just lock the back end of the tap tightly in a pair of vice grips and you can usually cut new threads like that. Use cutting oil. If it gets tough to turn stick a screw driver in a space in the vice grips for leverage.

 

Correct! You might have overlooked this in my related post?

 

This bolt appears completely ruined. Even the remaining thread is reduced in diameter and only maybe two turns are left. Imagine how low the torque has to be for avoiding to kill the remaining thread. And then imagine how easily the new nut may then come loose again.

There is, I believe, no alternative to either replace the bolt or to cut a new thread of lower diameter onto the remains of the bolt. Replacement of the bolt might be done by drilling out and positioning a rivet nut instead of the bolt in the chassis sheet. Then instead of a nut a bolt is screwed in, obviously.

In any case, do not overtorque again ...

 

Unbelievable: 7 pages and 133 posts for one stinkin' bolt.

Get a Dremel and a life, dudes.

 

Glad you got it resolved

If you don't have one you may want to get a in pound torque wrench. It is amazing how little torque those 6mm nuts can take. The typical torque for a 6mm nut is 80 inch pounds and that is only about 6 ft pounds.

Even though it is OBE, you had a question about how to tap the hole. Taps can be driven with an opened-end wrench and a many of them have a center hole on the back of the shank. This center hole is used when the tap is made and can be used to hold a tap straight while you are driving a tap-in with a a tap wrench or an open end wrench. A point like a center punch or another tap can be used to hold the tap in-line. The most effective way is with a pointed center in a drill-press chuck or a milling machine, but a center punch in your hand can be better than nothing.

 

Love to see some photo's of the
process, and the completed repair....

 

Well done again.

Certainly no waste of time in terms of the post count from my point of view. Interesting to see/read the various solutions offered.

 

If you have not already done it......

Next time you "service" that area,
you might want to consider some
strong LOCTITE to hold things well.

 

Just my opinion--if the nyloc's work fine?? how did this happen in the first place??

I have progressively reduced the diameter of a small bolt by use smaller and smaller dies and then used a external threaded insert as the conection between nut and bolt

 

It was overtightened. I don't know if the OP directly mentioned that but this type of problem/failure is most always indicative of that. Due to how nuts and bolts have differing properties for them to function as designed, in general the bolt will almost always loose the fight and it's threads get stripped or the bolt shears.