Removing Stripped Or Frozen Bolts And Screws
By Tom Neale
Photos by Mel Neale
You've been there. No matter how hard you try, that bolt won't come out. This can turn a five-minute job to one that takes days, resulting in a horribly expensive mess. There are tactics and tools that will often solve this problem, although I admit I've sometimes longed for a stick of dynamite. Patience, vibration, and wise use of force are key.
Doing the wrong things can wrench off the bolt head or strip the slot in the top of the bolt. Hopefully your bolt will have a head, such as a hex head, around which you can fit a socket or closed box wrench. If this isn't what you have, most good builders use sensibly shaped holes, such as the various Phillips type shapes, in the head for better tool gripping. Unfortunately, a few builders still use bolts with straight-edge slots, which easily round out. These require special caution. If your fastener has a rounded-out slot, you can often cut another slot into the head with a Dremel tool. There is no limit to tricks that good mechanics use. Generally, the information below applies to all bolts if you use the correct bit, socket, or wrench.
If your bolt doesn't turn after moderate pressure, first spray on a product like PB Blaster or CRC's Freeze-Off. The former is representative of products that have a lubricant, which will work its way into very tight corroded surfaces. CRC Freeze-Off also has penetrating lubricant but adds the feature of contraction caused by temperature differential. This product, if used properly, significantly chills or even freezes the bolt, causing it to contract, which hopefully facilitates entry of penetrating lubricant and separation of the corrosion. Usually it takes a lot of spraying, but when it works, it's worth it.
If the chemicals don't work, begin patient tapping to set up vibration. After each tapping session, add more penetrant. Depending on the situation, use a hammer directly on the bolt or on a box-end wrench that's held squarely and securely over the bolt head and torqued tightly by hand in the "unscrew" (usually counterclockwise) direction. This tapping not only sets up vibration but also, hopefully, tends to turn the bolt in the right direction as the vibration begins to separate the bind. Sometimes this process may take a few moments, sometimes days. Neither the hammer nor the blows should be too heavy. The goal is to create vibration, not immediately force the bolt to turn. If your hammer can't reach the bolt, you can transmit its blows to the bolt using a heavy-duty hardened-steel straight drift pin or similar tool, flat on each end, made for this use. Wear eye protection.
If you still have no success, try heat from a torch. Most people use a propane torch, but other sources generate far more or less heat. What you use will depend on what you're heating (remember, heat will transmit from the bolt to the surrounding metal), your familiarity with the source of heat, and of course, where you're working. It's seldom, if ever, a good idea to use open flame belowdecks, no matter how careful you are. Most use the simple inexpensive propane torch with easily handled, inexpensive canisters. The heat should be applied according to instructions for the products you're using. But generally, the tip of the flame should be just touching the bolt. As a practical matter, you'll probably want to direct the heat to the bolt rather than the surrounding metal because you may not want to damage the surrounding metal. And that metal, because of its mass, will probably consume the heat and spread it out before it does any good. If you're trying to remove a nut from a bolt, you should probably apply the heat or cold to the smaller nut.
After heating, try more tapping as well as more heating, if needed. After heating and tapping, spraying in a lubricating penetrant like those mentioned above often helps. With the effects of the heat and tapping, there may be more of an opening for this type of product to enter. Wait for the metal to cool; spraying one of these products on hot metal can cause fire and explosion.
Feel the Impact
Usually by this time, a wrench will turn the bolt. If not, there are a few more tools that may help. An impact driver can be invaluable. You've seen these quickly remove lug nuts from your car wheels in repair garages, except the ones there are usually pneumatically driven. Most of us use electrical impact drivers, battery-powered, or AC. I prefer AC drivers because of the extra power and unlimited run time. You must have the right-sized fitting for your bolt (a socket or bit to fit the hole in the head), and it should be made for use with an impact driver to survive the extremes of torque and stress.
Straight slots for screwdrivers often don't fare well with impact drivers or any other forceful device. If you're working with one, be sure that your straight-slot bit is exactly right, as to width and thickness, for your slot. Imperfectly fitting bits will ruin any fastener. There are also much-lower-cost manual impact drivers. These perform the same job, but not as well. You position the bit, turn the body of the tool to set the direction of the tool's rotational force, and then hit the hardened steel body of the driver with a hammer. However, these don't have the quickly repetitive directional pulse of the electric tool.
And then there's the Ultimate Weapon "proper" mechanics would never use. I'm not a proper mechanic. I'm just a guy who often desperately needs to get the job done on my boat NOW. So, sometimes I'll pull out my powerful and effective cheating bar. It's just a piece of pipe that I fit over the handle of a boxed end or socket wrench. It allows my puny muscles to exert much more force. But use this super tool with caution. It's easy to break the ratcheting assembly in a socket wrench or twist off the bolt head. Then you're really bolted (as in screwed).
Different lengths of pipe and different inside diameters round out this arsenal. Obviously you'll want thick-walled pipe. The longer the pipe, the more leverage (power) you can apply. Always be sure the wrench is squarely on the bolt head and not canted in the least. Failure to do this as you apply torque almost assures a headless bolt, and the odds are bad enough already. Also beware of the extra clearance you'll need for your lengthened "handle," particularly if there are electrical terminals or wires around. Normally I'll pull out a cheating bar before I go through all the steps above, because I don't have the time. I seldom use this trick after doing all the rest because I know that if the other tricks haven't worked, the cheating bar will probably just break off the head.
If you end up early on with a headless bolt, or a bolt or screw with the slots rounded out, you may want to try an EZ-Out. This is a hardened bit with sharp, hardened, counterclockwise-oriented edges that grip the inside of the properly sized hole, which you must drill into the bolt. Sometimes these will turn out the fastener. However, if you've already tried the steps above, this probably won't work. Not only are these tools difficult to use, but also they tend to break easily.
If all else has failed and you have a headless or rounded fastener, it's time to drill it out. Use your AC drill and hardened bits, marketed to cut steel or stainless. Drill first a small hole for centering and guidance, then a larger one in the center of the fastener, with a bit either the same size or slightly smaller than the body of the fastener. Sometimes, as you drill it out with a bit just slightly smaller than the outside diameter of the body, the remaining bolt walls and threads will loosen and crumble, leaving the surrounding threads intact. If you completely drill out the bolt or screw, rethread the hole and start again. If the offending fastener is stainless, plan for an excruciatingly long time of patient, careful drilling and the destruction of many bits. Keep the drill hole lubricated with drill bit oil as you work.
When you're installing that fastener, use a product such as Tef-Gel to prevent another lockdown. If that's not available, use silicone sealant or one of the grease products such as Never-Seez for this purpose. If you're dealing with stainless fasteners in aluminum, it's best to use Tef-Gel. You don't want to ever have to do this again.
— Published: October/November 2012
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How to simply create solid, near-permanent threads inside a damaged screw hole
Degree Of Difficulty
Materials and Costs:
- Tef-Gel, $14 for 12-oz. tube
- Manual Impact Driver, $23 Craftsman
- AC Impact Driver approx. $100 to $300 (depending on brand and store)
- Propane Torch approx. $15 to $25
- Cheating Bar - You probably already have one…
- CRC Freeze-Off approx. $7 to $14, depending on size
- EZ-Out Set approx. $20 to $30, depending on size of set
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