anyone got more info on this technique?

one of my old coworkers was an ex-airforce mechanic and i remember he mentioned that they would drill holes into the tips of cracks to stop the crack from propagating. iirc he called it 'stop drilling' but i'm having trouble finding more info on this.

we're currently repairing efini's original s4 SE and i've noticed a few cracks on the chassis. i was thinking about how to go about repairing or stopping them from spreading. i want to try stop drilling the tip, filling in the hole and then welding the crack. anyone have any experience with this?

No, but you could try this:

http://www.fatiguetech.com/coldEX_stop_crack.html

Yep, I've done it a few times.

One of the worst was a crack in the bellhousing of a Corolla. It certainl stopped the crack.

The main thing is to make sure you drill out the head of the crack, sometimes it's not even visible.

JB Weld it.

glad its been done and it works. i wasn't sure if i was remember it right since i haven't talked to the guy in years.

i think i'm going to drill out a relatively large hole beyond the tip of the visible crack to make sure i get the tip.

nice link dak. it looks to be a variation of stop drilling with a plug that does something to the drilled hole. can't find it for sale though. no biggie. i'm probably going to just RTV the hole. i'm a little wary about filling it with something solid...

why RTV the chassis? Get something stronger.

Haha, RTV wont do squat.

If it's a crack in the chassis, break out the welding gear.

He could make due with a metallic based chemical composition such as Apoxy, JB Weld or Welding Putty. Welding putty I found to be the strongest, but it takes a while to cure.

any time I've dealt with cracks in chassis stuff, all I did was weld it and it was fine.

anyone got more info on this technique?

one of my old coworkers was an ex-airforce mechanic and i remember he mentioned that they would drill holes into the tips of cracks to stop the crack from propagating. iirc he called it 'stop drilling' but i'm having trouble finding more info on this.

we're currently repairing efini's original s4 SE and i've noticed a few cracks on the chassis. i was thinking about how to go about repairing or stopping them from spreading. i want to try stop drilling the tip, filling in the hole and then welding the crack. anyone have any experience with this?

Stop-drilling cracks works but sometimes the crack continues on past the drilled hole, so you have to keep an eye on it for a while.
Usually, the hole you drill doesn't have to be that big, but you do have to make sure you hit that magic spot at the very tip of the crack. Sometimes, the metal is weakened beyond what you can see with your eye and your drill hole could be of no effect because the crack will continue in it's line after the hole. Normally, it's because you thought you drilled at the end of the crack but didn't see where the crack truly ended. Checking the area with a magnifying glass should give you a better view of the area and just where the crack ends.

I usually drill the smallest hole I can get away with while still getting the job done. Anything bigger is just a waste, and could end up weakening the structure if it's in a critical spot that carries a heavy load.

Keep in mind that stop-drilling is usually a quick fix until you can either replace the part or put a good weld in there to fix the area more permanently. In many cases, it will stop the crack in it's tracks, but in the end, you still have a crack in the part.

I can't really say much about filling the stop-drilled hole because I usually don't do it. I like to keep an eye on the drilled hole to see if the crack has really stopped or not. I'm guessing now, but I would think that if the crack doesn't continue after a few weeks, I guess you could call it fixed and go ahead and fill the hole with something.

One more key point: I'm basing my answer on aircraft repair and not auto repair. I'm not sure if that would make much of a difference as the intent of the stop-drilling is the same, just different metals most likely.

thanks for the info guys

im not RTV'ing the crack. that would obviously do nothing .lol

i was going to rtv the hole i drill just to keep water from getting in, and because im wary about filling the hole with something since the filler material and the metal around it will have different expansion properties

and i'm still going to get the crack welded