Removing broken bolts: any special tips?

[RC92234]

Yeah, in removing the water pump with bolts I'm sure hadn't been touched since being installed in May 1973, 3 of the ten broke.  Two nearly flush with the block, one with about one inch showing.

I know how, I've got the finest collection of left-hand bits assembled and Kroil Oil at hand (lol).  It's hard work boring directly into steel, but I know what I've got to do.  I haven't learned anything new from a slew of How-To vids.  I'm rather stuck at the part of keeping the bit in line with the bolt long enough to dig in -- I will try again to make a better dent with a punch, but I'm also thinking I don't want to hit so hard I just re-tighten the bolt.

Just posting this in case there are any special "been there, done that" tips from the hive mind.

 

[Don C]

Start with a small drill bit. I doubt if left hand bits will remove the bolts, they are rusted tight, not broken off by over tightening. I prefer easy-outs. Hitting the center punch hard may loosen some of the rust, it will not make it tighter unless you hit the threads.

I would also let them soak with penetrating oil over night, and apply more before you start trying to remove them.

 

[Kilgon]

I agree with Don. I have a set of tungsten carbide bits I keep aside just for drilling broken bolts. There's no easy way just have to use the tools you got.

 

[Bentworker]

A hammer and pin punch is a good first step. I would grab a pin punch that is the size of the minor diameter of the thread or a little smaller and give the broken bolt a few good raps with the hammer and pin punch - with the pin punch square to the broken fastener.

Next I'd get a center punch and do your best to punch the broken fastener right in the center.

Drill the broken fastener with a pilot bit, then choose a drill about 2/3rds the diameter of the broken fastener. IE- use a 1/4" drill on a 3/8" bolt. Drill the pilot all the way through the broken fastener, that way you can squirt some penetrating oil in there and get it working in from both sides of the fastener. I've never used a left hand drill bit because 95% of the time you need an extractor anyway.

Buy some good extractors - you can get some from McMaster-Carr. You don't want to skimp here since this is what is going to make the difference between extracting the bolt, or having to drill it out and helicoil it.

Use lots of penetrating oil.

Use the extractor to remove what is left of the bolt.

https://www.mcmaster.com/extractors

 

[Don C]

+1 on the good extractors, if you break one off in there you'll have real problems, you won't be able to drill it out. Which brings up another point, make sure you don't apply a side load, you want to apply torsion directly down the extractor. Don't use the extractor to support the wrench when you turn it.

 

[turtle5353]

I rarely drill them anymore. I weld a nut to the stud sticking out. And use a ratchet to remove like a normal bolt. Even if the bolt is broke almost flush I can usually get my mig welder down into the nut and fill it with weld to penetrate the broken bolt. The high heat helps loosen the bolt also. Works for me almost every time.

 

[RC92234]

Anyone seen that movie "The Money Pit"? *sigh* That's what you step into with old cars, right? You shouldn't get into the hobby if you're not realistic about that, but the enduring mystery is "how deep?"

I was spending a small fortune eating up cobalt bits and making no progress, so I brought in some professional help for a better assessment of the remaining two broken bolts. It wasn't good. Well recommended local guy said besides that both bolts are deeply jammed (one embedded with a broken bit, the other with a well-embedded broken tap), I'm now past the point of accomplishing much with just hand tools. But more importantly, now both the cover plate and start of the hole is buggered up, and it's going to take a machine shop to be able to re-align and re-bore the holes. That means pulling the engine and a brand new set of... ahem... "adventures".

So he took a few photos and sent them off to a well-known machine shop down the valley and got an answer pretty quickly: nope. Even in a machine shop the worst of the two is past the point of working on because the tap went off center. Replace the block.

Pardon me for a few minutes will I ponder that.

Replace the block...

Replace the block...

Replace the block...

And all that was really necessary to replace was the leaking radiator and power steering pump but I thought "while I'm at it, let's do alternator and water pump, too!" Live and learn.

 

[Don C]

I wouldn't give up yet. "Professionals" and machine shops don't take chances, they don't want to be blamed.

By tap, do you mean that you were trying to re-thread the hole or do you mean an extractor? If it's an extractor I hope it the type that has the tapered shallow reverse threads and not the fluted, drive-in, type. Is it just off center, or did it go into the block? How did the bit get jammed and broken? Is any of either one broken off above the block?

Maybe some pictures, straight on and oblique, would help us come up with something. A lot of us learned things the hard way and/or have had to fix other people's screw-ups.

 

[RC92234]

I wouldn't give up yet. "Professionals" and machine shops don't take chances, they don't want to be blamed.

By tap, do you mean that you were trying to re-thread the hole or do you mean an extractor? If it's an extractor I hope it the type that has the tapered shallow reverse threads and not the fluted, drive-in, type. Is it just off center, or did it go into the block? How did the bit get jammed and broken? Is any of either one broken off above the block?

Maybe some pictures, straight on and oblique, would help us come up with something. A lot of us learned things the hard way and/or have had to fix other people's screw-ups.

I'll get you some photos, but no not an extractor, a tap.  Close to impossible to drill out with hand tools it seems.  It's about 3/4" in. The hole itself is problematic because we attempted to drill down *beside* that tap in the empty part of the X shape of the tap itself.  How it went off center, I dunno.

Photos pending. Thanks --

 

[Bentworker]

How did you end up with a broken tap?

 

[RC92234]

How did you end up with a broken tap?

I'm not sure how to answer.  "Sh*t happens"?

If I recollect correctly (because it wasn't me) a good deal of the bolt had been drilled out, small bit then gradually larger until about all that was left stuff in the threads, so we tried to use a tap to clean that out thinking the tap would follow the good threads, not the askew broken bits.

 

[RC92234]

Photos  

First:  both remaining bolt holes.  Second:  close-up of lower of the two (with broken tap and broken drill).  Third:  close-up of upper of the two with the messed up hole and a pit of pick left embedded.

 

[turtle5353]

Yeah, you done F’d that up son.

 

[Hemikiller]

It's absolutely possible to fix that, you need either the correct tools, or find a true machinist - not an automotive machinist.

There's a method to spot anneal the broken tap and drill bit with a piece of metal rod. You spin it with a drill against the broken tap until it reaches the blue temp stage and then let it cool. You should then be able to drill through the broken bits.

 

[Bentworker]

It could be fixed - but not without skill and cost- and most likely removing the engine as it would be time consuming to build a fixture to do the work in place.

Based on your results so far (and I am trying my best to not be abrasive) It does not look like an extractor (easy out) was used (which was what was suggested). The method executed did not seem to match any of the ones suggested on the forum. As you have discovered once you mix hardened high speed steel into the mix from the broken drill bit and the tap things get much more difficult.

There are tap extractors, but they are finicky and honestly that looks so chowdered up that I wouldn't give one much chance at success. You would have to purchase one the correct size for the broken four flute tap you have entombed in your engine block... Again, like a 5-20% chance of it working. They have four tabs that engage the flutes in the broken tap, and are pretty flimsy. Work okay on taps that get broken off by side force, not so much for taps that get broken by rotational force from being bound by chips.

Next option is carbide tooling. Based on the photographic evidence I suggest you DO NOT try carbide tooling. A skilled machinist could pull it off, but the last thing you want to do is break off carbide tooling in the hole and create more of a problem.

Thermonuclear option is what is called a "tap disintegrator" It is basically a crude EDM (Electrical discharge machining) machine that uses electrical current to disintegrate whatever is conductive in front of it regardless of hardness. Real machine shops have tap disintegrators and the skills to use them.

Once someone gets the remainder of the hardened tooling and bolts out of the hole the nest task would be to place the block on a milling machine and correctly locate the centers of the holes, and machine for threaded inserts since they look like they are off center enough and wallowed out beyond what could be repaired with a Helicoil. Another option would be to machine a jig with drill bushings, and use that to relocate the holes in the correct spot. That might allow it to be done in place, if you could somehow get out the broken tap and broken drill (or drills???).

It's a bummer that it turned into as much of a disaster as it did.

What happened is a good reminder to pause and take a look at the suggested speed and feed rates for what you are drilling, use quality (not hardware store or harbor freight) drills, use lubricant, and finally stop while you are ahead if possible...

Keep asking around at shops, and don't be surprised if the bill to fix is a half day labor.

 

[RC92234]

The biggest issue was most likely pushing beyond *my* endurance and yet still proceeding allowing error to enter the process yielding failure as a result.  I copped to all that.  Nonetheless, this is where I am and the forward looking comments are encouraging.

Now about this thermonuclear option -- obviously that's a machine shop thing, but it's the first I've heard of it.  Sounds very promising; now to find a shop that does it.  And I do tend to think once the crap in the holes is out, it seems there's enough block left to bore over and use something like a c-sert to secure and 'down size' to the size of the std 5/16" bolt.  Is there a more usual name for this EDM technique so I know what to ask for when I start my calling around?

Oh, and half day labor?  Considering otherwise the engine is trashed, --> not a problem <--.  I'm good until about halfway to "you should have/could have just replaced the engine"  :chin:

Thanks!

 

[Don C]

http://cammann.com/

 

[JimB73]

“A series of unfortunate event” for sure, but you have a great attitude about moving on and getting the problem resolved. Good luck with getting it done and getting your car back on track.

 

[rvrtrash]

I believe the EDM method is also called Laser Cutting. I had my machine shop do one bolt I had stuck in a block, and then they welded and re-drilled the hole. It worked out great.