Removing a broken bolt.. well, the end of the process at least!

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Tugboat

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Nashville, TN
I broke a bolt off inside the case while removing the transmission/water pump cover.
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Using left-handed bits, I drilled it out to 1/8" and inserted an extractor but couldn't get it to budge. I even made a little platform out of a Dremel case and some scrap wood to help keep the drill level. This process took about 2.5 hours.
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After hitting it with PB Blaster, Kroil, etc for about a week, I figured I'd give it another shot. I'll be using these extractors:
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Like I said, I've been soaking this sucker in Kroil every time I've gone downstairs for the past few days. I drilled the bolt all the way through at 1/8 and then again at 9/64. Had my buddy heat up the case with a torch, then tapped in the extractor and gave it a twist.
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No go. I could feel the extractor slipping inside the bolt. Tapped it again with a hammer to better seat it, and my buddy gave it a twist. The vice grips he was using slipped on the extractor and made a loud "SNAP!"... I thought that it had broken off inside, but luckily it was just the slip and we were able to wiggle it back out. Here's how it looked:
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I kept slowly drilling, stepping up to 5/32, heated the case, tapped in the extractor, twist... nothing.
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Up to 11/64.. at this point, the first parts of the threads are starting to pull loose. I grabbed it with some needle-nose pliers and pulled it out. Reinsert the extractor, twist, nothing.
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Finally, I drill out at 3/16, which is about is big in diameter as the bolt itself. Since my camber is a bit off, I'm not drilling exactly through the center of the bolt, but catching some of the "upper left" - 11 o'clock-ish - of the bolt's threads and, as the bit exits the back side, into the aluminum case. Not much, just a bit. Here's the hole at this point:
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At this point I'm ready to give up and haul the whole bike over to a guy who can properly fix it. While I'm opening another beer, my buddy looks around at the backside of the bolt and, seeing that there is hardly any metal of the bolt left, and that the backside is not corroded, uses a punch to "bend in" the remaining parts of the exposed threads.

Well, I guess that tapping was enough to dislodge the rest of the threads, and, well, here ya go:
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The remaining threads:
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When I originally broke this off, I had a hard time getting the shank out of the hole in the cover - presumably because when it broke, the torque caused the end to flare. The same must have been true with the threads that were inside the hole - the flared, lodging them up into the threads in the case and thus would not come out. You can see how it's not corroded at all.. It must have just been the buggered first few threads that were holding it in there.
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TL;DR: I broke a bolt, then took my time and some heat and penetrant and was able to finally extract the broken piece.

I'm borrowing a thread restore kit this weekend and we'll see if the remaining threads are still usable.
 
Nice work! And nice photography! A lot of effort for one stubborn little bolt, but well worth it. The extractor also expands the bolt slightly, so that plus the distorted threads at the break point must've really hung things up. Congrats on the removal!
 
I'm thinkin' the "Drill 3/8" is the best hole size for the extractor to work with, and the extractor size is No 5. :headscratch:

Craftsman tools made in China? Tell me it isn't so!?!?!? :crying:

I hope I'm wrong! :beg:
 
When I was in the Navy, I watched a machinist drill out a broken bolt by using the same method. He was really good at what he did so his hole was dead center on the bolt. He stepped the drill bit up gradually until he was able to simply grab the little thread that was sticking out of the hole with a pair of needle nose pliers and pull the remains of the bolt out of the hole like it was a piece of wire.

Too many times I have twisted extractors and heard that snap only to find that the extractor broke off in the bolt. I have remembered that trick and was able to use it last summer when I broke a starter bolt in the engine block. It sure is great when it works well in the end.
 
Good job!

brianinpa":qkms725s said:
When I was in the Navy, I watched a machinist drill out a broken bolt by using the same method. He was really good at what he did so his hole was dead center on the bolt. He stepped the drill bit up gradually until he was able to simply grab the little thread that was sticking out of the hole with a pair of needle nose pliers and pull the remains of the bolt out of the hole like it was a piece of wire.

Too many times I have twisted extractors and heard that snap only to find that the extractor broke off in the bolt. I have remembered that trick and was able to use it last summer when I broke a starter bolt in the engine block. It sure is great when it works well in the end.

What counts for success is when the bolt is out. :Egyptian:

The closer you are able to drill dead center, the closer you are to success. :clapping:

I try not to use the extractors at all. The best plan is like you described, stepping up in drill bit size until you can pull thin threads out like a wire spring. Sometimes the broken bolt is in a place that is difficult to access, making this technique pretty much impossible. Then you gotta improvise the best you can.
Patience is your friend!
 
Hi

New guy here adding his 2 cents to this topic.

First off, nice job sticking with it OP!

One thing to keep in mind when a bolt twists off because it's rusted is that if the strength of the bolt isn't strong enough to break the rust bond, I doubt an extractor is going to be able to apply any more force.

Now, if the bolt was sheared off instead of twisted, that's another story and there isn't the holding power of rust in the threads. An extractor would be the perfect tool here.

Another thing to keep in mind. All extractors are not created equal. The Snap-on brand comes highly recommended. I prefer the spiral types as opposed to the vertical fluted ones. I feel the spiral bits in better.

If you do have to drill the broken fastener out use a center punch with a lite tap. Check to see if the point is centered. If it isn't, angle the punch a bit and move the mark until it's centered. Another method to get a punch mark in the center would be to use the mating part hole as a guide for a transfer punch.

Now, with your small (~1/16) sharp bit, start drilling. Is it still centered? If it isn't centered angel the drill just a little to move it into center and then straighten it back out. (be careful not to snap off the bit) Work your way up to the drill that is the tap size for the thread. Run a tap through and you're done.
 
ShaftDrive":ewj0ii8s said:
Hi

New guy here adding his 2 cents to this topic.

First off, nice job sticking with it OP!

One thing to keep in mind when a bolt twists off because it's rusted is that if the strength of the bolt isn't strong enough to break the rust bond, I doubt an extractor is going to be able to apply any more force.

Now, if the bolt was sheared off instead of twisted, that's another story and there isn't the holding power of rust in the threads. An extractor would be the perfect tool here.

Another thing to keep in mind. All extractors are not created equal. The Snap-on brand comes highly recommended. I prefer the spiral types as opposed to the vertical fluted ones. I feel the spiral bits in better.

If you do have to drill the broken fastener out use a center punch with a lite tap. Check to see if the point is centered. If it isn't, angle the punch a bit and move the mark until it's centered. Another method to get a punch mark in the center would be to use the mating part hole as a guide for a transfer punch.

Now, with your small (~1/16) sharp bit, start drilling. Is it still centered? If it isn't centered angel the drill just a little to move it into center and then straighten it back out. (be careful not to snap off the bit) Work your way up to the drill that is the tap size for the thread. Run a tap through and you're done.
Great info :eek:k: :thanks:
 
Impressive job. We have a local mobile guy that all he does is travel around to workshops extracting broken bolts. Almost as keen as another guy that sands things for a living.
 

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