Engine Builders vs. Broken Bolts and Studs
And the winner is…
By Brendan Baker
It’s probably one the longest standing feuds in mechanical history. Removing broken bolts and studs has resulted in very high rates of aspirin usage among frustrated engine builders. Is there any way to make it less painful? There are a few.
A number of tools on the market are supposed to "extract" or "aid" in the removal of seized or broken fasteners. And many of these gimmicks are just that – gimmicks. Often times these tools are marketed as the solution to all of your problems, but only cost money and create more problems.
Another factor in the whole "bolt extraction saga" is the time involved in removing them. It takes time to drill out a bolt in several incremental steps. Then, you have to tap it and put an insert in the hole, too – adding more time. You can also burn up a lot of time soaking parts, smacking them with hammers and heating them up with your torch.
Why They Get Stuck
There are three common problems with removing broken or stubborn fasteners, according to Paul Pavlinovich, editor of www.SteamEngine.com, an Australian-based Web site devoted to steam engine restoration. He says that corrosion (rust or other oxidation) is a major issue for old engines with similar metals.
On older engines, especially cast iron blocks with iron or steel bolts, corrosion seems to be the most common problem engine builders face. "The rust locks the fastener’s threads fast in a hole," says Pavlinovich. "In its early stages, you will be able to shock the bolt and break the rust. In its later stages, the base metal of the bolt/stud and the block will have become partially fused together. Once this has occurred, only heat will resolve the problem."
Newer style engines don’t have as many difficulties with corrosion because the metals are generally not the same. "The metal in the block is usually different than the metal in the bolts and studs, e.g., aluminum/aluminum), so block corrosion is less of an issue. It does occur, but only shock will be required to break the bond because the dissimilar metals won’t fuse," Pavlinovich explains.
The other areas of concern, especially with classic engines, are the past use of thread sealants and crossed-threads. Cross-threaded bolts can sometimes be a problem that engine builders have to correct. Cross-threading is when the bolt threads and the hole threads don’t marry properly. "This is usually indicated by the fastener being difficult to turn on insertion," says Pavlinovich. "It should be backed out and inspected then reinserted correctly. It may be necessary to chase the threads in the hole and on the fastener to clean them up."
Finding Your Mojo
According to our Jay Steel, owner of Taylor Engine, Whittier, CA, it’s not worth it to fool around with gimmicks or shortcuts. The winner of the 2003 Engine Builder "Machine Shop of the Year" Award, Steel is an expert in restoring old engines, often with stuck fasteners.
"The best thing in the world is just to center punch the bolt or stud, getting as close to center as you can; then start with an 1/8˝ drill bit and work up,” Steel says.
From his perspective, spiral extractors may be tempting to use, and sometimes work, but Steel says they often just break off and create a bigger problem than he had in the first place.
One tool that does seem to work well for Taylor Machine is a Goodson stud removal tool (p/n PSR 500). "We do a lot of Flathead Fords and they have 48 studs in them. We used to break 30 to 40 percent of them, which means three to four hours just drilling the studs out," Steel says. "Since we started using this tool, instead of breaking off 20 studs, we’ll only break off two or three. We wear this tool out; we use it that much."
A common technique for removing fasteners is to use heat. However, there are many different ways you can use heat. "A lot of people heat them up and then use paraffin wax to loosen the fastener," says Steel. "A combination of heat, shock and soaking works best to remove bolts and studs."
Steel says, "We use a product called Kroil®, the ‘oil that creeps,’ and we’ll soak them in that and apply heat as well. If it’s a stud in a Flathead, I’ll squirt it every morning and bang on it with a big hammer, which will shock it. Often times it’ll come out when it wouldn’t have before."
Some engine builders say that the heating and rapid cooling of the fastener will break the bond between the bolt and the workpiece. "Heating alone expands the fastener and is employed to break the rust bond," says SteamEngine.com’s Pavlinovich. "When you use heat, as the fastener slowly cools the bond can reform. The best method is to heat the fastener then quickly quench it with a wet rag (be careful of the steam because it can scald)."
Using too much heat on both aluminum and cast iron can cause damage to both. It is therefore best to heat just the bolt or stud and not the surrounding area whenever possible. Cast iron can harden if exposed to too much heat, and aluminum may anneal and become susceptible to cracking.
For broken studs and bolts, using a welder to "build up" material on top of the broken piece is a popular technique. Marlo McGraw, shop foreman, Waterhouse Motors, Tacoma, WA, says, "I use the TIG welder to weld on to the broken bolt and build up a nipple area about 1/2˝ high. By that time the bolt is pretty hot,” he explains.
I then clamp onto the nipple area with a pair of vice-grips and then shoot the bolt with WD-40, which cools the bolt quickly and also lubricates it. After this, 90 percent of them come right out."
According to McGraw, Waterhouse workers don’t drill out very many bolts anymore since they started using this technique. He says this same technique can also be used on TE plugs (thermaclear emissions) as well.
Paul Nelson, instructor at Northwest Technical College, Bemidji, MN, also uses a welding technique to remove broken fasteners. "If you have a little bit of a broken bolt sticking up, you can put a nut onto it and weld it up full," he says. "This does two things: it gives you something to grab onto and the heat transfers into the broken bolt. A lot of times it comes out this way."
Nelson says that the times that he does have to resort to drilling, he uses left handed drill bits, which work especially well on broken bolts due to overtightening. He stresses to his students the importance of center punching. "If you’re off center and you start drilling, especially in aluminum, the hole will wander and it won’t be in the same location anymore," he adds.
"The best thing that I’ve seen for removing bolts is a Metal Disintegrating Machine (MDM)," says Nelson. "They can be expensive – around $6,000 to $10,000 for a new one, but shops I know that have them love them and couldn’t be without one. It has an electrical probe that uses electrical current to burn out the fastener."
‘Hey, Go Get The Disintegrator!’
John DeBates, Auto Machine, Inc., St. Charles, IL, says he took a chance and purchased a used Uni-Tek MDM a few years ago and now couldn’t live without it. DeBates says it works well not only on his own automotive jobs, but he also uses it for a growing number of non-automotive work. He says that he is providing an invaluable service to his industrial customers because when their production equipment breaks it can cost thousands of dollars to sit idle. DeBates can even take his MDM to the site as a portable unit to cut out a broken bolt.
The extra benefit of an MDM is that you can get jobs from many different industries and it’s much more profitable because you can charge more for industrial work. "It’s a whole different price structure for those outside of the automotive industry," says DeBates. "Many job shops have $100 or more invested in a single die. If they break a tap off at the last minute and it has to be shipped off tomorrow morning, they don’t care how much it costs as long as you can fix it quickly."
Dave McNamara of Uni-Tek Manufacturing in Frankfort, IL, says his metal disintegrating machines use rectified DC cutting power to cut through bolts and studs and just about any other type of metal that conducts current.
It is similar to a welder in that it uses polarity to remove material. It vibrates electrodes at about 120 times a second, so the electrode makes and breaks contact with the workpiece at 120 per/second. Water is fed through the center of the electrode to flush the particles out of the hole. Uni-tek’s MDMs can burn out metal fasteners from .080˝ up to 3-inches, most automotive applications will fall into this range.
The beauty of the MDM is that there is no drilling involved, says DeBates. It creates sparks from arcing and pulsing, constantly making and breaking contact with the fastener. It functions on the same principle as when you touch a positive terminal to a negative terminal. If you look closely after touching booster cables together, there is a crater on the positive clamp and an equal amount of material added to the negative clamp.
DeBates says it’s changed the way his shop operates. "We threw all of our other bolt removal tools away – it just doesn’t pay. On a very rare occasion we find one that we can’t setup on an MDM, but those are few and far between."
DeBates and others can attest to the productivity and profitability of MDMs. On the business side, it can generate typically between $30-$35 for a broken tap that is relatively easy to set up. "I did a job recently where I was able to remove 12 exhaust manifold bolts in under an hour to complete the whole thing." And at $30 a bolt, that’s $360 an hour!
There are many options to consider when fasteners give you grief. Choosing what works best depends on your specific needs. And though the feud may still continue between engine builders and stubborn, broken, cross-threaded fasteners, it should be comforting to know that there are tools, techniques and machines that can help you win the battles ahead.