Broken bolt extraction - how would you handle this?

[widebody911]

Both lower engine mounting studs on my Type III motor snapped off. Long-story-short, the threads on the originals were getting haggard, so I replaced both studs. I don't think I got as much as 10 ft/lbs on them before the snapped, and they snapped about 1/8" or so inside the case. Tried drilling them with a brand new bit, but it barely scrapes the surface. I suspect the metal was too hard and brittle, so when the threads were cut it created a stress riser - they were probably toast before I even installed them.

Oh, and I used blue LocTite when I installed them.

[crustychief]

Try a saturated alum mix. you would have to get creative building a dam to hold it in there though, plus it would take a day or two.

[manbridge 74]

I would get about 3 cobalt bits, a punch and a torch (MAPP gas would be safest to start). Get the punch mark DEAD center. Start with small bit and go in a very small amount. Check that your hole is centered and angle over slightly if not. Once center is assured keep drilling upping size of bits until almost stud size is reached. You will need a third eye during all this to make sure drill is level on up/down plane. Now that your hole is perfect use the torch to heat case outside of stud melting Loctite. Stick the largest easy out that fits in hole and tap in with hammer. I'd actually try left handed drill bit during last drilling size but assuming you don't have them. Don't use a ton of force turning easy out or it will break. Should start turning easy if it's going to come out at all.

It is also essential to have a large amount of wherewithal on hand....

[widebody911]

Get the punch mark DEAD center. Start with small bit and go in a very small amount

I've done this much already. Even a brand new cobalt bit won't do much but scratch the surface - this stud is very hard. I'm using cutting oil, too.

[billybek]

I have used a dremel tool and a combination of carbide cone bits to centre the hole on extremely hard broken bolts and once centred, used a ton of drill bits to drill and enlarge the hole in the hole in the bolt.
Or
Take it to a machine shop.

[manbridge 74]

Hmm, maybe try a different brand of bit? Or dremel with a small stone to get down through work hardened area then drill.

[sc_rufctr]

Do you have small masonry drills?

[John Rogers]

I had that happen many, many years ago. Since I was working in my garage at home I took the engine to a well know VW engine race shop which mentioned this happens a lot on the engines used in off road race cars. It took them about 10 minutes to get both broken studs out and they took a grade 8 bolt slightly smaller then the broken ones and used the bolt as a welding electrode and welded it to the piece of stud. Waited a couple minutes and backed then both out. I had not used any Locktite but the heat would have loosened it anyways.

I would not try this but find a shop, either a VW repair shop or machine shop that could do it. Back then my fix cost $5.00!

[Charles Freeborn]

Carbide tipped masonry bits are intended for hammer drills - not what you want here.
Google "Diamond Grinding Burrs", and be prepared to heli-coil the holes when you're done.

[javadog]

I would use a really small torch, emphasize the really small part, to aggressively heat the very center of the studs. Get them hot enough to kill the Loctite and to also anneal the studs themselves. While the area is smoking hot, melt some candlewax to use as a penetrating agent. Obviously, this works if you have the thing standing on end and you can puddle the paraffin on top of the holes. Then use the best quality, left handed drill bit you can find to drill through the studs, and enlarge the holes until you can use some sort of easy out to back them out.

[908/930]

How fast are you spinning the drill bit? should be slow approx 300rpm with lots of pressure and sharp bit. If you have a industrial supplier near you can pick up a small solid carbide drill bit, that will get through but they are very brittle, and you don't want to break one of those in there.

Once you get a hole in, there are easy outs that are fluted they work quite well, some heat to release the lock-tite.

[908/930]

I just looked at what they want for a solid carbide drill bit now, a little pricey, you can sharpen up the tip of a good quality 3/16 masonry bit and that should get you through if it is only the surface that hardened, keep the drill sharp though even if you have to resharpen every 5 or 10 seconds, the heat from drilling can be work hardening the material in front of the drill bit.

[Por_sha911]

I know this is heresy to some but;
How much would it cost to have a machine shop extract those for you?

[widebody911]

I went out and bought a bunch of masonry bits. The only one that seems to be effective is the Bosch "Blue Granite Turbo" bit. It's almost deep enough to break off an EZ-Out in it.

[herr_oberst]

I'm with John Rogers. Find someone who does this.

And then buy ARP studs to replace the broken parts.

[CBRacerX]

Now that you have gotten this far, it's time for the high quality left hand bit just a few thousands smaller that's the hole. It will probably remove the remaining stud bits. Worst case, you drill too big and have to time-sert the hole.

[widebody911]

Originally Posted by Por_sha911

I know this is heresy to some but;
How much would it cost to have a machine shop extract those for you?

I do not know, but I would probably have to dismember the motor to do so.

[racerabbit]

easiest and best way to remove a broken bolt, especially in an aluminum case, is grab a nut the same size as the stud, grab your handy welder,and build up a weld on the end of the broken stud, slip the nut over the weld nib, and weld it into the nut. serves two purposes... puts lots of heat into the stud to loosen it up, and gives you something to turn. works every time.

[porsche tech]

^^^^What he said. Have done this many times removing broken studs/bolts from aluminum with a mig welder. Like racer says, works every time.

[widebody911]

I have done that many times, but in this case, the stud was about 1/4" "below grade" and there is a flange that would prevent turning the newly-created bolt.

Originally Posted by racerabbit

easiest and best way to remove a broken bolt, especially in an aluminum case, is grab a nut the same size as the stud, grab your handy welder,and build up a weld on the end of the broken stud, slip the nut over the weld nib, and weld it into the nut. serves two purposes... puts lots of heat into the stud to loosen it up, and gives you something to turn. works every time.