Broken crank bolt

[JGuy07]

Long story short, had a dumb-dumb moment and used a bolt to help install/thread on the hub. It broke and I'm pretty sure it's seated down all the way into the crank. A 3/4" section of the bolt is what is down in the crank so there are still some threads available in the snout. I've tried taking my drill and using a bit to drill out a hole for en extractor, but not luck. The bolt didn't break smooth and I was unable to accurately center the hole since it kept sliding off the center (raised pointed spot from break). The drill hole is off center which isn't going to allow me to easily use the extractor. So what are my options here?

1. Redrill a bigger hole trying to center it better and use bigger extractor.
2. Drill a slot or groove to use heavy duty flat drive to twist out the bolt.
3. Find a drill bit to slowly grind away at the bolt to break it down for removal.
4. Forget about it, install the hub and pulley. They fit snug anyway and maybe I can use a smaller bolt to help hold pulley on since there are still threads available in the snout to grab.

Any advice on what I could do is appreciated. Car has been MIA for quite some time and if this hadn't happened I would've been done with all my work this wknd and back on the road. Thanks in advance.

[BIG CAT]

can you get a pic of the snout?

[MoeHorsePower]

You need to get the piece out, do not try and use the remaining threads or you will be asking for trouble. Here is what I did when that happened to me, I took a ball file, its just a file that looks like a ball that goes on the end of a drill. It was small enough to fit in the snout of the crank, I made the surface of the broken piece concave, then I took a center punch, punched it in the middle of the broken piece, started with an .040 drill bit and worked my way up until I could get the correct size easy out to fit and out came the piece. Make sure you use a quality easy out, if that break then you are SOL..

[95ImpySS]

I agree with Moe. That sounds like your best bet at this point. If you cant use an easy out (remaining bolt it too tight), youll have to drill it all the way out and use 2 HeliCoils, or tap it out one size larger.

That's quite the predicament your in.

[JGuy07]

I'll get a pic when I'm out there to show what I'm looking at. But, I was also told that since it's seated and I basically stretched the bottom threads because I kept torquing it until it broke that I'm going to have a heck of a time using an easy out extractor to remove it. So, was told to look at my remaining threads. If I can get a minimum of 5 full rotations out of a new shorter bolt then it will hold the pulley well. I have plenty of threads left, should I try that route? I don't think trying to redrill a center hole will work as I have already widened the hole I have enough for my extractor to fit and since it's off center I won't be able to get a good center punch for a restart.

[95ImpySS]

You "can" go that route. It's not optimum but if its your only option go for it. I have seen MUCH MUCH worse done on cars in Miami. To help extend your thread count, if the bolt your using has a tapered edge. Remove it. Put a nut on the threads and run it past where your plan to cut. Cut as strait as possible with hacksaw. The remove nut to chase the threads again. Use hefty amounts of blue lock-tite in and make sure the hole and bolt are oil/grease free.

[JGuy07]

Does anyone know the depth of the crank snout where the bolt goes?

I figured I would use plenty of blue loctite on the new shorter bolt if I had to go that route.

[JGuy07]

Ok, good news and bad. Good news is that I was able to center a new hole and got it drilled pretty deep if not all the way through the broken bolt. Bad news is that I still can't get it to budge. The extractor grabs good and hard now but its extremely hard to turn it and when it does turn it's only stripping out. So now idk what to do. what now?

[RamAir95TA]

Post up a picture like you said you would. :)

[JGuy07]

I added the pics, the clarity isn't very good but I think you can manage to see what I'm talking about. One is the first hole off center, and the other is with the new centered hole.

[RamAir95TA]

Question....Why don't you have the seal and hole covered with tape/plastic/ANYTHING? You're getting huge chunks of metal directly into your oil pan with your drilling. Yikes!

At this point I'd consider drilling a new LARGER hole right through the old bolt and old threads, then use a Timesert (www.timesert.com) and install a larger bolt. Stock is 7/16" x 20 - I'd step up to a 1/2" x 20 (fine thread, 1/2" bolts are usually x 13 TPI). Keep in mind that means drilling a LARGE hole greater than 1/2" across to fit the Timesert, and it MUST be perfectly straight. I would use a TiN coated high speed bit slightly larger than your current hole, then step up one 1/16" in size each bit until the hole is the proper OD for the Timesert. This will prevent overheating of the drill bit while keeping the hole straight. Make sure you use cutting fluid as well (I recommend Tap Magic) to make the job go smoother and prolong the life of your new expensive TiN drill bits.

Granted you could get away with using cheaper stuff, but the last thing you want is a tool-steel drill bit broken off in your crank. Then you're f*cked.

[JGuy07]

There isn't any shavings falling out of the hole while I'm drilling, I cover the area with my hands and I blow out the shavings. You're right though, there is still the chance I'm getting bits in there. I'll look into the timeserts. Would it be possible to keep drilling the hole bigger until I neared the threads, and then just use a rethread kit to follow up the threads?

[RamAir95TA]

You could, yes, but I wouldn't recommend it. It's best to start with fresh uncut metal and go with the Timesert.

Then again I don't half-ass things so I'm sure someone will come in and say it's perfectly fine. :)

[JGuy07]

Went back out today to try and finish the drilling and such. Purchased a Cobalt steel bolt remover kit (OEM brand). Figured since it's main purpose was removal of broken bolts the strength of these cobalt bits would have been of the better material, as some are weak only for wood and the best grade would be for steel such as the case in my situation. The bits are also titanium coated so figured I was set. Wrong, literally under a second of drilling the bit shattered into a few pieces. I was able to get the shards out and the hole was fine, the bit didn't cut into the bolt at all. The set I got was all I could find after going to stores here in town and thought it was what I needed.

Now, I'm trying to find a good set of LH titanium nitride coated bits and I'm sure that these would have to work. If not, then I certainly have one heck of a problem on my hands. Anyone know of a good set like I mentioned?

Found these, although they are RH they should still work I would hope.
http://www.harborfreight.com/29-piece-titanium-nitride-coated-drill-bit-set-5889.html

LH bits: http://redmoonbay.com/cart.php?target=product&product_id=3162

[96LT1355Z28]

I'd steer clear of HF drill bits. You can get away with buying some stuff from them and saving some $ but there's no way to improve a drill bit. Sounds like the Cobalt stuff you bought was too hard and that's why it broke.

[95ImpySS]

I second the notion. Anything from Harbor Freight used in you situation will fail and cause you more of a headache. Harbor Freigh is the cheapest of cheap. Visit a local hardware store and get a Cobalt or TiN bits. I cant say which is harder, but I have experience with Cobalt and it holds up very very well. Avoid, Ryobi, Dewalt, OEM, Milwaukee, etc. Pretty much any drill bit set you can get at your local Home Depot/Lowes. They are junk for such a special drilling situation. As well as such hard metal. Expect to pay anywhere from $5-$45 per drill bit. Much cheaper that removing the crank. I would listen to RamAir95 very closely. He has offered great advice.

When drilling, use high speed and VERY VERY light pressure. You don't want the sharp new bit to dig in too quickly and break. Hold the drill as steady and strait as possible. I like to use a weak drill. Helps prevent the bit from snapping. I use a small 12v Milwaukee drill. Use large amounts of coolant/lubricant. I use CRC Cutting Oil. The TimeSerts look much better than Helicoil's. I have never used them, but they seem like a much more stable product.

Good Luck

[RamAir95TA]

Truthfully any quality drill bit should work. Drilling is more a matter of technique than anything else though. I prefer MEDIUM SPEED, light pressure, and TONS of cutting fluid (like I mentioned above). Notice I said cutting fluid, not WD40 or something similar. Prepwork is important too, getting a properly centered pilot hole, punch, etc.

Technique, technique, technique. In my 11 years of working on engines and ammonia screw compressors I've never snapped off a drill bit when having to extract a fastener.

I still stand by my original suggestion though. I guarantee your ordeal would be over by now. ;)

[JGuy07]

The drill I have has level indicators built in so I was keeping my eye on them. Maybe I just got a bad set of cobalt bits? I applied light pressure to get it started and then it snapped. I'm still learning as to what methods and tools are best for different situations, so not sure on what brand is best suited. I posted another link from Cal-Hawk but I guess that would be a cheaper brand as well. I am unable to find anything besides the set I already purchased which broke. The set had a few sizes but they jumped alot so I wouldn't be able to gradually increase the bit size, which is probably why it broke so easy. Any other advice on what set or brand to get? Thanks.

[JGuy07]

Ok, I'm working in the limited space with the motor in. So it's a tight squeeze. How difficult, for me, would it be to follow your suggestion? Is the snout easy to drill out? I mentioned the Cal-Hawk set and a link I gave, slow and steady with that set should work. Just worried about drilling in the snout since it's a first.

[guppymech]

If your drill bit is not cutting the metal you could have work hardened the end of the broken bolt. If that is the case you'll need to use a high speed burr and remove the top layer of work hardened material and use a new drill bit, preferably a drill bit made out of cobalt (shiny nickle in color) to drill your hole. I've always drilled hard materials with a slower speed and medium pressure with plenty of lube or cutting oil.

[JGuy07]

I'm actually thinking of trying to find a carbide bit and just removing everything with the bit and then re-threading. Ram is right it would be easier and I would've been done by now if I just did that from the start. Only question now, what actual bit do I use to redrill/widen the hole when the bolt is finally removed? A reamer or just a normal like carbide bit?

[guppymech]

Trying to save the threads is preferable to me but if that is not possible you could heli-coil the hole. There are Tap and Drill charts that specify what size drill and taps to use for each size of bolt. You need to understand bolt thread nomenclature, ex: minor and major thread diameter. Search the web for information to learn these things so you don't ruin your crankshaft.

[JGuy07]

Threads can't be saved, my awesome noob like status with the drill caught them a few times. So, what size drill bit would I need in order to drill the new hole in order to use an insert to bring it back to the normal 7/16?

I have drilled out all but maybe 1/16 of the bolt and its thread locked and seated so it won't budge. I'll drill a completely new hole like ram mentioned. So what size drill bit do I need now? If I enlarge the hole I would also have to redrill the center hole in the hub wouldn't I? (This being without the insert and just rethreading to use bigger bolt)

If insert is used, I am completely lost at exactly what to get. Been reading on helicoils, timesert, threaded inserts etc and they all have pros and cons that come with precise drilling size and installation. I found a price for timeserts and the kit would be over $100 or so for the simplest kit I found online. Kit contains drill bit, counter bore, tap, install tool and inserts. That price is still out of my range for now after buying all the bits earlier used for drilling. I know what I need to do, and then I know what I CAN do or have funds for and they are different. Whats the best route now guys?

[JGuy07]

What about this, not sure about the brand though...? "Helical"? Something like this would be what I need?
http://www.grainger.com/Grainger/Helical-Thread-Repair-Kit-5WE94

Was told to use a drill bit that is 1/64 larger then the size I actually want when using inserts. So, I want a 7/16-20 then my drill bit or new hole size would be 29/64, is that how it is done or is that wrong? Drill the new hole, rethread the hole with same thread count desired (20) and then install the insert. I haven't read up on the process yet that's just what I was told.

*****Had longer post with details prior to this but not showing up until 'approval'

[z28cam70]

that kit looks like a generic helicoil. time serts are much stronger than helicoils. most gm dealerships use timeserts as it is the method that GM uses to repair damaged threads. i have used timeserts in numerous applications including repairing stripped rocker arm studs with great results. save your money and do the job right the first time it will save you time and money in the end. the only other way i would repair this would be is to rethread the hole for a bigger bolt but it is easy to break a tap off in the hole and then you would be in a worse situation than you originally started.

[JGuy07]

Yea, rethreading a completely new hole for a bigger bolt was on my mind too. It would also ease the mind knowing the new bolt has a firm hold throughout the entire threads rather then just a small section of where the insert is. But, I would also have to drill the hub center hole larger. I have a tap set already, would just need the larger drill size and make sure I have enough cutting fluid.

(Finally found them) Oreilly sells the helicoil kits which have the inserts, tap, and install tool for under $30 though. People have good luck with helicoils as well. Would just need to make sure the hole is straight and be careful with drilling again. I think I got some good practice while drilling out the bolt o.0

[Chris]

Reading through this, sounds like a perfect reason for a stroker crank

[JGuy07]

If this wasn't my DD now and I had time and the cash...oh the possibilities that have crossed my mind :D

Inserts are out, new bolt size is in. Jumping up to a 1/2" and grabbed a 1/2" cobalt & tungsten bit with carbide tip. Will drill out the snout to hold the new 1/2" bolt. Will also use a drill press to help with drilling the hub. Grabbed plenty more cutting and rethreading fluid as well as a bulkier t-wrench for the tap. I've been working with the rad and condenser still in so I'm probably going to have to take those out in order to get enough room with this larger bit and the drill I have. Hope this goes well. Any other advice to give for enlargening the hole and rethreading?

[guppymech]

You better STOP and read how to drill and tap holes. You do not use a .500 size drill to make a hole for a 1/2 size bolt. Look at the link for the tap and drill chart below.

http://buydrillsuk.co.uk/wp-content/uploads/2011/07/Tap-Drill-Sizes.jpg

[JGuy07]

Was under the impression the imprints on the taps indicated what size drill bit required. My 1/2 tap in the set I have has a separate set of stamped numbers reading 1/2" so I figured that was the drill size. I know there are different taps which require different things, but just made an assumption and guess I was wrong. So would I use the 29/64 bit to drill the new hole in order to use the 1/2" bolt? Can't seem to find that size anywhere around here since that was the size I was looking for when considering the inserts.

The tap I have is 1/2-20, and I guess I'll have to search more for the new bit.

[RamAir95TA]

Did you even read about the Timeserts? The kit include everything you need to make the hole, including the proper size drill bit.

http://www.timesert.com/html/inchsert.html

Ugh.

[JGuy07]

Yes I did, but when looking them up the kits I was finding at the cheapest were still over $100....not an option for me. I couldn't find one for less let alone a decent distributor.

[guppymech]

Was under the impression the imprints on the taps indicated what size drill bit required. My 1/2 tap in the set I have has a separate set of stamped numbers reading 1/2" so I figured that was the drill size. I know there are different taps which require different things, but just made an assumption and guess I was wrong. So would I use the 29/64 bit to drill the new hole in order to use the 1/2" bolt? Can't seem to find that size anywhere around here since that was the size I was looking for when considering the inserts.

The tap I have is 1/2-20, and I guess I'll have to search more for the new bit.

Considering the consequences of ruining your crank I would recommend that you look into all the options out there, You're about to enter the school of hard knocks.

From the referenced tap and drill chart a 1/2 20 bolt takes a 29/64 drill. A 1/2 13 (course thread) bolt takes a 27/64 drill. Since you are having trouble finding a 29/64 drill bit, the next smaller bit is 7/16 which is .0156 smaller. In soft material I would try the 7/16 bit but the crankshaft is very hard material and I don't know if I would use it. The chart says 29/64 for a reason. You will need three 1/2 20 taps. A taper tap to start the threads, a plug tap to do the majority of tapping and a bottoming tap to finish threading to the bottom of the hole.

[RamAir95TA]

Considering the alternatives given your situation and timeframe to find a solution $100 seems pretty reasonable.

Hope your drilling/tapping works out okay. Good luck!

[JGuy07]

It isn't bad, I just don't have funds for it. Unpaid internships of over 40 hrs a week does that. Good advice though don't think that I'm not understanding, but it's just a route I can't go at this time.

The tap set I already have, and a drill bit of around $17 seems easier on the pocket atm. Just to clarify again. To use the 1/2" bolt I would need to use my 1/2-20 tap with a 29/64 drill bit? Thanks.