Good morning Scott,
Do you have to work on those or do they just keep coming naturally??
Anyway, no, there is no 90%. Now, don't remember all of earlier post, look at 7.7.1.3 in the 2010 edition: "Flash Requirement. Studs shall exhibit full 360° flash with no evidence of undercut into the stud base.
Combine that with some of other references made already on repair and replace look at the commentary for 7.8. We can bend any number of studs we want to a 15° angle to verify soundness. If we don't like the looks of them, no matter how many their people have already 'rung', bent, or whatever, we can bend more.
So, bend them. If they don't come loose or at least tear, they are good to go.
Now, the flash is made up of molten metal that is pushed out from under the stud and comes from both the stud and base metal (I'm sure you know but thought I would start at the beginning and walk through the process). With the shields in place the 'spray' of the metal is controlled and contained to produce the flash around the base of the stud. That spray will often exhibit discontinuities if you will that if it were a weld would be unacceptable. Things like the appearance of lack of fusion- nonfusion on legs, porosity, small shrink fissures, etc. Most of these are acceptable as long as the flash is complete for the full 360°. It may be higher in one area and lower in another. Some may term it incomplete because of these discontinuities but did it produce flash all the way around? If so, it is good. But, if you are unsure, bend it. Don't just ring it, bend it to a 15° angle. Code says you as the Verification Inspector can do that. If you are the contractors in house, you can too. At least smack that baby good and hard and see if she burps. You would be surprised how many I have had go flying that had a 360° flash. I often grab a 4 lb and ring all of them on a member with a pretty good smack.
Bottom line, the flash doesn't have to be a perfect, defect free, ring of tightly adhered metal around the base of the stud. But it does have to be present for the full 360° circle.
All of us have slightly differing views of the gray area between a perfectly sized fillet weld and undersized, between repairable overlap and leave it alone it is acceptable, etc. There are those repair areas that are no brainers. There are welds that are beyond question for acceptance. But there are areas where one of us would accept and another reject and/or even we ourselves would call it one way one time and the opposite the next time. So also with studs. You won't get a perfect solution for some of those in that area. It is a judgement call even if we don't like to admit that we make those. 'It either meets the code or it doesn't!' YEAH RIGHT. Good luck with that one.
But there is no wiggle room for 90%. The code says a full 360° or repair or replace. The question is if the 360° flash is 'pure' enough? Usually so. I look mainly for those that go into the stud. Sometimes you can look at the base and even with a 360° flash you can see under the edge of the stud. OOPPS. Not good. Even if it stands up to my hammer blow it needs repair.
Don't know what else to say. Studs are a different animal. Horses I think. Some men think they are, studs that is.
He Is In Control, Have a Great Day, Brent