Anyone who has ever worked on older vehicles has experienced the dreaded broken bolt malady. It may be on your bike or on someone else’s, but it always ruins your day. Why do they always seem to be in an awkward and hard-to-reach place?
Trying to remove one by drilling straight into the remaining bolt, and then using an EZ out can be trying and sometimes, still doesn’t work; sometimes it can even make the grizzly situation worse.
In my shop, as the perfect example, I happen to have a motorcycle engine case containing a dreaded a broken-off bolt (photo 1).
I didn’t know about it when the engine lower-end was delivered nor did the owner, but when I went to remove the bolt, it turned super easily. It turned but would not come out. The reason? The bolt had previously broken and the past owner tried to hide it by coating a stubby bolt with silicone and then pushing it into the hole! It looked real, like the bolt was doing its job holding the cases together, so he could sell it. A very dishonest motive, in my opinion.
There are several methods to removing broken bolts, and I use a few of them in my shop, depending on the job and circumstances. The method I like to use most is welding a nut over the broken bolt. This works for me most times and is usually a very quick, strong, and successful method.
Notice, I said usually. Always take your time and don’t rush it! In photo 2, you can see I used a 7/16-inch nut over the 3/8-inch bolt. It gives me a little additional room to allow for welding it together easily. I usually go at least one bolt size larger in diameter, but in a few cases I have gone up to an even larger size, for leverage or welding access.
First, sand the zinc coating off the nut to ease in the TIG welding. Just put the nut on a sanding belt and remove the zinc coating. Notice in photo 3, the one on the right has had the coating sanded off. You can also drill out the nut to remove the coating on the threads. I don’t generally find any issues welding it with zinc-coated threads. TIG weld the nut onto the broken bolt (photos 4 & 5). Be sure to get the broken bolt hot enough to penetrate it with welding rod. Then it is time to try to remove it.
Sometimes the bolt will slip out easily, but most times it will not. There was a reason why the bolt broke off in the first place. Could have been a bad thread and someone forced it, or a too-long bolt bottomed out against the case threads, or it may have been over-torqued. Many people use a cheap hardware bolt where a grade 5 or case grade 8 was the specified bolt.
In this scenario, it was still hard to remove (photo 6) as with the other bolts I removed, since the previous person (notice I didn’t use the term “mechanic”) who worked on this used red thread-locking adhesive. Don’t try to force out the bolt/nut assembly because it may result with the nut breaking off the weld or breaking the bolt again.
Using an oxygen/acetylene torch, I heated up the case area (photo 7) where the bolt threaded into. Red thread-locking adhesive when heated becomes solvent. In this situation, the aluminum case will expand greater, over a steel or cast threaded bolt. This allows a loose fit and aids in the removal process. While heating the case, I kept tension on the wrench and in a short time it turned with little effort and came out (photo 8).
There are also some new penetrating lubricants like WD-40, Yield, or The Fabulous Blaster. They can help a lot, if you have time to let them soak into the treads.
The result always brings a huge smile to my face (photo 9) because it’s like saving the patient’s life. Plus, I know reassembly will be handled with all the proper fasteners in their rightful spots.
It is important to be sure you clean up the threads (photo 10). Use the correct lube and tap the hole. Take your time and clean the tap if necessary. The holes in this case cleaned up nicely for a 1962 engine (photo 11), and when I showed the owner, he was quite pleased.
Taking your time is important because rushing any job can result in more overall work and stress. Now, get out to the shop and do some wrenching!
Sources
Brew Dude
http://www.brewracingframes.com/
Let’s start with the English lesson: brew (broo). It’s a full fabrication and machine shop. We build quality handmade bicycle frames and frames available in road, track, ss, mtb, cx, and touring. We won numerous motorcycle shows, and we have full powder-coating facilities in house. We can build the bike of your dreams using quality products made in the USA. He does ceramic coatings, any color, and writes tech articles for The Horse, American Iron Garage, Ol Skool Rods and of course the badass Bikernet.com
Car Kulture Magazine
http://www.ckdelux.com
