Originally Posted by The Machine

Sorry to read this before you ruined the threads. The answere to a cross threaded hole is always to drill out the first few threads with the full diameter drill (5/8-11 thread 5/8 drill). You must go slowly until you get good threads. Once you have good threads the bolt will go in easily and the drilled out section will act like a guide to prevent future cross threading. If you are concerned with strength you can tap the hole a little deeper and use a longer bolt but in most cases you would be fine without the longer bolt. Any time you cross thread a hole the odds are one in a million that you would start a tap at the right point to match the old threads and in the worst case you could be 180 degrees off which would cut your threads in half and almost guarantee a striped thread.
Now that the damage is done, the easiest repair is a helicoil, but I would have one concern. This thread is going into a tube which is welded into this frame. If this is correct, you must be sure that the helicoil will be supported by enough material. The OD of a 5/8-11 helicoil is .742 min .767 max. If for example the tube where 7/8 dia, you would have only .054 wall left((.875-.767)/2) which would be too weak to safely be used especialy for a suspension support piece. I would think you would be safe from 1.062 OD tube and up. That would give you a minimum wall of .145. Remember that part of the strength of a helicoil is the force which is applied outward on the helicoil which both locks it in to keep it from comming out but also keeps it from stripping. This force is what would concern me as the preasure exerted could cause the pipe to crack and or yield enough to allow the helicoil to spread out too much and let the bolt pull out. There is some good news, in that there is a section of the frame that the tube is welded to that will give some added support but remember that a 5/8-11 thread has a pitch of .0909 which means that if the frame is 1/8 thick you have just over one full thread engaged in the farme section itself. I would be glad to give any other info that would help. BTW, the drill size for a 5/8-11 helicoil tap is 21/32 (.656). Good luck.

Originally Posted by 1961TUX

Mr. Machine it's 5/8-18 not 11.