broken head stud repair?

[shbop]

Well, I've got two broken studs at just a touch over spigot height. Tried using both the tig, and mig yesterday to attach a nut, then a tapered bolt, to get them out. No joy! The divilar remnant just seems to brittle. So I'm left with what feel like harsh options. A local machine shop wants to set the case half up, and drill them out, replacing with a time cert. The other option, is to crate the block and sent it to the west coast where this type of repair is a daily event. Thoughts? Ideas? Thanks in advance!

[jpnovak]

Here is my saga a few months ago.

A friend starts having a strange Putt-putt noise on his engine. Turns out that there is a broken head stud on lower outside #1. Yep, His 83SC had lower dilivar studs

Next thing you know, the engine is out of the car, heads are off and we are pulling studs. Using the usual method of heating the case spigot by the stud using the Oxy Acetylene torch is mostly working. We managed to pull 9 of 12 lower studs with no problem.

One of these remaining was the initial broken stud. I tig welded a nut to the top and with a little heat it came out easily.

Remaining stud #2 broke about 1 cm above the case spigot. Enough room for a welded nut. Again, the tig welder to the rescue, or so I thought. The nut welded easily enough. Then after some heat, the stud started to back out. Next thing, Snap. The stud broke clean below the newly welded nut. I guess it was really time to get these out of the motor. Dilivar bad

This remaining stud material was almost level with the spigot. Time for plan B. Grab a bolt, clean the end. run a TIG bead around the base with no problem. This time, more heat and the remains succumb to a CCW rotation. Yep, out at last.

Remaining Stud #3. Of course, the last stud is the worst. We started with the OA torch heating the spigot. With the double nut on the top we started to turn it out. It went about 1/2 turn and then broke level with the spigot. I thought there was enough room for a nut. I welded a nut. The tiny filler I added to the middle of the nut ran down the side and into the recess in the spigot formed by the diamter of the hole. Crap. The nut held but I could not turn it as it hit the case. We tried anyway. The stud now broke clean at the nut, just like #2. I got a bolt out and started to weld. This stud would not take a bead no mater what I tried. It just would spit and sputter and not melt. I finally got a bolt welded only to have it break off. AFter several cycles I thought we were done. We started getting out the phone book looking for EDM. I thought we would try one last thing.

Drilling these studs is next to useless. Yes, we tried this too and broke 3 bits. Crap.

Using the dremel cleaned up the stud remnants. By this point they were flush with the case. I then laid a bead of weld on top of the stud forming a mushroom. The TIG filler is soft and allowed us to center punch and then drill a small pilot in the soft material. Next we started grinding with the Dremel and a carbide cutting bit. After about 45 minutes we milled down 8mm using small circular motions. This was deep enough for an extractor.

We seated the extractor with the hammer and began heating. The entire case was so hot we could not touch it but stud finally backed out. Victory at last.

Here is the carnage.



For reference, here is the carbide cutter that actually managed to cut the dilivar stud. I was not hopeful when we started but was ecstatic at the end results.




What a fun way to spend a Saturday. Wrenching and burning metal.

[KTL]

You know of a shop that does EDM? It's supposed to be fantastic for removing broken studs w/out having to drill.

Pelican Technical Article: EDM Broken Bolt and Stud Removal - 911 (1965-89) - 930 Turbo (1975-89)

Helluva job by Jamie. Nice perserverance!

[shbop]

Hat's -off Jamie. I went through the same process with the other four. The last two were real problem children. The nut kept breaking off just like the one in your pic. I had a good weld. The divilar just crumbled underneath. Machine shop service is challenging here. While I would much rather have the stud out, if I can't get it; is time cert the next best option? I've got one broken stud in each case half, of course. So shipping costs to California will be enormous.

[shbop]

Originally Posted by KTL

You know of a shop that does EDM? It's supposed to be fantastic for removing broken studs w/out having to drill.

Pelican Technical Article: EDM Broken Bolt and Stud Removal - 911 (1965-89) - 930 Turbo (1975-89)

Helluva job by Jamie. Nice perserverance!

Kevin, I'm going to check again today, but I think it unlikely I'll find a shop with an EDM. Life in paradise has a few drawbacks, especially if you're into working on 911 motors.

[HawgRyder]

I became the proud owner of a set of diamond drill bits years ago.
Many "friends" have tried to borrow them...but to no avail!...LOL
I use them in cases like this...with lube and gentle pressures...they cut through just about anything...and by stepping up in size...I can get an easyout to fit.
Perhaps an investment of a few dollars would set you up too.
Bob

[docrodg]

With a careful hand and a dremel anything is possible

[shbop]

Originally Posted by HawgRyder

I became the proud owner of a set of diamond drill bits years ago.
Many "friends" have tried to borrow them...but to no avail!...LOL
I use them in cases like this...with lube and gentle pressures...they cut through just about anything...and by stepping up in size...I can get an easyout to fit.
Perhaps an investment of a few dollars would set you up too.
Bob

Bob, I've looked at quite a few sets. Would you mind sending me a link to what you have, if still available...thank you! pm or e-mail works great.

[jsveb]

Originally Posted by KTL

You know of a shop that does EDM? It's supposed to be fantastic for removing broken studs w/out having to drill.

Pelican Technical Article: EDM Broken Bolt and Stud Removal - 911 (1965-89) - 930 Turbo (1975-89)

Helluva job by Jamie. Nice perserverance!

It is fantastic. It must be possible to find a shop. If you cannot find a machine shop with edm, then look for a major metal fabricator, meaning industrial. I found an edm at a windmill plant. When/if the mess up some of the tower flange I.e. with a bit. They have to get it out, or risk loosing lots of money on that one unit, hence they got portable edm. It was amazing!

I have since then bout my own unit on eBay. Needs better cooling and a precision rig, but the basics are there.

There are blueprints online for building one, I bought a book on it. It can be done.

Anyways, back to you OP, sorry for the diversion.

[Lapkritis]

Originally Posted by docrodg

With a careful hand and a dremel anything is possible

Could cut a flathead slot into it and heat the case around it... strength, patience and heat.

[shbop]

I thought I struck gold when I found an article in the "Journal of Manufacturing Science and Engineering", authored by a young guy who now teaches at UH, on Electrical Discharge Machining. EDM. My excitement was short-lived as the young professor said he was a transplant from the University of Michigan, where the research was performed. So far, no EDM's on Oahu. Paradise has its' limitations. So now with thoughts turned toward the marvelous "dremel tool", I proceed slowly ahead. Four broken divilars down. Two to go.

[HawgRyder]

Jon...I wish I could get you the info on the drills...but...I originaly got them from the quartermaster in charge of the tool crib on the base I was stationed at!
All of them are aircraft length (long...some as long as 12").
I have seen sets for sale over the years...but I have been lucky that none of mine have been broken.
Since I got mine...I have noticed that drills of different materials seem to be preferred (other than diamond) so perhaps you might look at the latest alloys instead.
Bob

[safe]

You must heat the case!
If you do that you don't need a lot of torque to get the studs out.

[keynsham1]

I have been heating the case with a butane blowtorch. Is this too cold? It takes ages for any heat to get into the case. I find it hard to imagine it ever affecting the threadlock on the studs!

[Lapkritis]

What material is your engine case? Aluminum of magnesium?

[Ken911]

First of all if you need heat use a map torch not enough heat with propane. Second if your on Oahu and know someone who works in the ship yard you can probably get it EDM'd out for a case of beer. When i was there in the navy you could get anything for either a case of beer or a 20 pound tin of coffee.

[shbop]

Originally Posted by Lapkritis

What material is your engine case? Aluminum of magnesium?

Aluminum

[shbop]

Originally Posted by Ken911

First of all if you need heat use a map torch not enough heat with propane. Second if your on Oahu and know someone who works in the ship yard you can probably get it EDM'd out for a case of beer. When i was there in the navy you could get anything for either a case of beer or a 20 pound tin of coffee.

Too funny. I've got friends at the shipyard. It was one of my first thoughts after striking-out in the regular machine-shop world. No joy...

[safe]

Originally Posted by keynsham1

I have been heating the case with a butane blowtorch. Is this too cold? It takes ages for any heat to get into the case. I find it hard to imagine it ever affecting the threadlock on the studs!

Butane/propane will work, I use that. But you need a really good one, those that has a cheap one-time-use gas canisters will not work.

My propane heater uses one of these refillable bottles, with a Sievert Powerjet torch:



The difference is like night and day compared to the cheaper bottles. The heat output is more than double.
I heat the case around the stud for 45-60 seconds and the stud comes out easy.

[Lapkritis]

If you use a direct flame them be sure not to let it rest in one area of the case for long. You can melt the case if you direct the flame in one spot for a long time.