Removing stuck fasteners
by: 1166737157, Cobalt327, Crashfarmer, Crosley, Cucumber1949, Eloc431962, Grouch, HenryHighrise, Jon, Lanier Ledford, Schnitz, WakBordr7387
( to edit this page anonymously, or to be credited for your work.)
- Be safe. Position yourself such that if your hand slips, you're not going to hurt yourself. It is usually safer to push away from yourself (if you slip while pulling, a wrench to the face/ribs does not feel good). Best practice is to fit yourself with appropriate mechanic's gloves in the event you slip or the fastener abruptly moves, hands can impact adjacent objects.
- No matter what technique is used, when removing stuck fasteners, you need to pay attention to what is turning and what is not.
In theory, there should be nothing to stop you finger-tightening a bolt until it's snug, or easily loosening a bolt once it has been fastened snugly. In practice, it's often quite hard to turn some bolts or loosen other bolts, even when they are slack. The reason for this is that dirt gets stuck in the bolt threads, and it gets trapped when you start tightening the bolt, making it harder to turn. This is a warning sign -- if you can't finger tighten a bolt until it's snug then there is something wrong. If you are trying to put a bolt in, then take it out and clean the threads. If you are trying to loosen or remove a stuck bolt, see if you can access the end of the bolt (opposite end of the bolt head). Put a little grease on the threads before you try again. It's a bad idea to get out the spanner wrench early on to try tightening a bolt that isn't turning smoothly. Even if you get it tightened, that dirt is still in the threads, and it's quite likely that it'll jam the threads when you try to next remove the bolt.
Methods for removing stuck/frozen fasteners
Most stuck fasteners are stuck because of corrosion -- usually rust. There are at least three effective methods to break loose a fastener:
- Mechanical movement -- often simply a whack with a hammer.
- Differential heating -- making one part expand more than the other.
- Chemical penetrants.
Tighten, then loosen
In some cases simply tightening the fastener and then loosening it will do the trick. In some cases, wiggling the fastener back and forth may be helpful.
Strike it with a hammer
Though this may not be practical for all situations, a stuck bolt can often be broken loose simply by hitting it on the head with a hammer. In such a case, a brass drift may be helpful. Drifts of varying lengths can be made from brass bar, and used to access hidden bolts. Brass is used because it's softer, and thus less likely to damage the head of a fastener. Brass hammers are also available and one about 3 or 4 lbs. in weight is good for this.
Another option is to get a wrench or ratchet onto the stuck fastener, and then hit the wrench or ratchet with a hammer, creating a manual impact wrench.
If you can access the nut, try hitting each flat of the nut with a drift punch and ball peen hammer.
Smack it with a hammer #2
This method is useful when dealing with a bolt that is rusted very tightly. A lot of people will get a wrench or ratchet and push against it with a steady force. Doing this will more than likely break off the bolt head of a rusty bolt.
The best thing to do is to get a wrench or ratchet on it, and either hit it with your hand or a hammer several times. The sudden force will break the bolt loose with less of a chance of twisting off the head.
Some times a home made impact wrench will work, get a cheap wrench that fits tight and hit it with a hammer watching carefully that it isn't coming off the fastener. It's important when loosening this way to use a tight fitting wrench like a 6-point box end, as a loose fitting one will round the bolt head.
Tap it for a few minutes
Lightly tap on rusted fasteners for several minutes, apply a little penetrating oil, lightly tap a little more, then remove the rusted fastener.
Hammer a close-fitting metric socket tightly on a SAE nut, or vice-versa. Then use breaker bar socket wrench (or longest you can fit in a cramped space) to turn it.
There is a product that works basically the same way, but the inside of the sockets are lined with sharpened flutes that are also angled to dig further into the rusted nut or bolt as you turn the wrench. These are called BOLT EXTRACTOR sockets, and bite extremely well into round and rusty bolts and nuts, as the flutes are sharp and point counter clockwise. Think of what you would get if you made a mold of an extractor drill bit. See Special tools section.
Hot and cold
This method uses alternating heating and cooling. The resulting expansion and contraction is thought to break a fastener loose from the grip of rust.
- With a welding torch, a hand-held propane torch, or a combination MAPP gas/oxygen torch kit, heat up a bolt head until it turns red.
- While it's still red-hot, squirt it with water.
- Repeat the heating and cooling process again with the torch and water.
When using the "Hot and cold" method be sure to follow proper safety procedures. Specifically:
- Wear proper safety attire including welder's gloves and safety goggles.
- As with any time you use any flammable ignition sources, have a fire extinguisher within arm's reach.
When using the "Hot and cold" method, care should be taken to ensure that only the bolt is heated. If the nut is heated and cooled, the nut will likely become seized tighter.
When using this method use this Hot and Cold method FIRST... If you use any type of penetrating oils, they tend not to let the water do its thing when the hot and cold method is used. Please remember heat, & then use the water... several times. I think the water becomes steam which has plenty of penetrating power to get in tight places. You never heard of penetrating oil engines, but everyone has heard of steam engines.
- Too much heat will destroy the temper of the bolt. Important bolts (brakes) should then be replaced with new as the untempered one if reused could fail.
Heat the nut method
Heat the nut with a torch until red hot, cool the bolt with a good shot of spray-on rust remover then remove the nut while still hot. Heating the nut thermally expands it, while the rust remover (which is a refrigerant) thermally contracts the bolt. Be careful and use gloves as the nut and your wrench will be hot.
The heat and paraffin wax method
- Heat the bolt with a torch.
- Touch the threads with paraffin wax. Ensure that the bolt is situated such that the wax will run down into the mating threads.
- Remove the bolt.
The weld-on-a-larger-nut method
- Place a close-fitting washer over the top of the bolt to protect surrounding material.
- Take a nut that is larger than the actual thread of the broken bolt, and weld it to the broken bolt.
- Weld in short bursts until the weld fills the nut. This will heat the bolt but not the surrounding material. Using a 6011 welding rod in a stick welder has been reported to work well.
- Let the welded nut cool completely without using any water or spray. The bolt will contract and break the grip of the rust.
Some more info on welding on nuts.
- A tig welder is the welder of choice.
- It is critical to put some penetration oil like Kroil (and not WD-40) on as it cools just low enough for the oil to not just boil off. This will draw oil into the hole. This is the only time I have seen penetrating oil actually penetrate a stuck bolt.
Penetrating and lubricating oils
Penetrating oil is an extremely low-viscosity oil that can penetrate into the area between threads on fasteners. A stuck fastener is sometimes repeatedly heated, sprayed with penetrating oil, and then tapped with a hammer.
If heating or hammering is not possible the penetration can be improved by first spraying brake cleaner on the stuck fastener and following with the penetrating spray before the brake cleaner has evaporated. The solvent penetrates better than oil and will pull some oil with it.
If I could have only one chemical tool, it would be "Liquid Wrench". Note that when trying to loosen rusty parts, it's important to first remove as much of the rust as possible with a wire brush. Once it's as clean as a wire brush will get it, apply Liquid Wrench, then give the piece repeated light taps with a hammer for ten or fifteen seconds; this helps work the Liquid Wrench into the crevices. Wait two minutes, then repeat the Liquid Wrench/tapping procedure. After repeating the procedure 3 or 4 times, THEN try to loosen it with one swift blow. Sometimes it won't work, but the majority of the time, your patience will allow you to not only remove the rusted nuts and bolts, but to possibly even reuse them.
Many people recommend "PB Blaster", which led to me trying it - it did an excellent job for me. An overnight soak-in is an important step.
Some recommended penetrating oils
- Acetone mixed with Automatic Transmission Fluid
- Acetone mixed with Power Steering Fluid
- Air tool oil
- BG In Force
- Break-Free CLP
- CRC Industries: 5-56, Freeze-Off, Knock'er Loose, Ultra Screwloose
- Diesel fuel
- GM General Purpose Penetrant and Heat Valve Lubricant #1052627
- Hilco Lube #5035
- Liquid Wrench
- LPS: LST, KB 88
- Mouse Milk
- Nuts Off
- Paraffin wax
- PB Blaster
- Ronson Multi-Lube
- Schaeffer Penetro 90
- Seafoam Deep Creep
- Zep 45
Removing corrosion from metal fasteners can help in their removal. When the iron in steel converts to iron oxide, or "rust", it swells, which can cause parts to seize in place. Rust can also distort the head of a fastener hampering efforts to securely grip the head with tools. Corrosion Removers work in various ways depending on their chemistry. Some require parts to be soaked, others can be sprayed on applied as a gel. Methods of corrosion removal include:
- Mild household acids - typically require a multi-hour soak
- Vinegar (Acetic Acid)
- Citric Acid - Usually available in bulk crystal form.
- Commercial Proprietary Removers
- Electronic Rust Removal - Requires a bucket, sodium carbonate (washing soda), and a 12v battery charger.
- A pneumatic or electric impact wrench can loosen most any fastener, given enough tool capacity and psi. But that is not always going to be on hand. The following are some ideas that may work:
- Flameless heat tool useful for removing rusted or broken fasteners: The Inductor.
- Left-handed drill bits, or screw extractors, can be used to remove many fasteners.
- For stubborn nuts, try a nut splitter. It will crack the nut without damaging the bolt inside.
- A rechargeable impact drill/driver can be used to loosen frozen fasteners if they are within the capacity of the tool.
- Hand-held impact drivers typically have slotted and Phillips headed bits, as well as a socket fitting. The bit or socket is placed on the stuck fastener, and the other end of the impact driver is struck with a hammer. The impact of the hammer strike loosens the fastener, the downward force keeps the bit in its place, and the impact driver turns the force of the hammer strike into a sudden torque on the stuck fastener.
- Craftsman 10 pc. Damaged Bolt/Nut Remover Set, Low Profile Bolt-Out Sears item #00952166000. They are useful for when the bolt head is rounded off, or there is no room to beat a socket or wrench on to it, or when a torch is not available.
- Another good brand of bolt extractor is named Extractor, it has a little bit more "bite" than the Craftsman and Irwin extractor tools.
- Hotrodders forum thread on the "GrabIt" extractor tool, as seen on a late-night infomercial.
Instructions for making an impact-type screw removal tool
This is designed to remove a fastener that has a stripped head.
- Get an aircraft rivet gun (note: not a tubing cutter, they're too fast) that has less than 2000 b.p.m. (blows per minute).
- Get one of the rivet gun sets, and weld a piece of 3/4" hex stock to the working end of the set then weld an apex tip holder to the hex stock (of course you need an air compressor, 100 psi is just fine).
- Put a Phillips tip in the apex holder (prior to that grind a little off the tip as they usually are slightly too long; this will allow the tip to drop farther into the screw head so it will pick up what is left of the flutes in the head).
- Put the whole thing together and insert the tip into the screw head. Slowly pull the trigger on the rivet gun, while at the same time putting pressure on the box end wrench you have installed on the hex part of your tool, making sure to keep pressure on the gun handle so it won't jump out of the work.
- One word of caution -- even though this works almost 100% of the time, it is possible (if the screw is into a plate nut) to drive the plate nut off its mount.
Tips for broken-off bolt heads
- If enough of the bolt remains, try to grab it with locking pliers or a pipe wrench.
- Try to saw a groove in it, so that a flat-head screwdriver can be used to turn it. Use an impact screwdriver if you have one, it will work a lot easier.
- Take a 12-point socket that is just larger than the shaft of the bolt, and beat it down onto the bolt with a hammer. Turn it out with a ratchet. When finished, put the socket in a vice, and tap out the broken bolt.
- If a bolt is broken off below the surface, build it up with a welder until there is enough to which to weld a nut. If this breaks off try it again, this method is the best, the heat and cool cycle of the TIG weld will loosen the fastener in the stuck piece.
- Center punch the broken bolt and drill the bolt head using a left hand drill bit about half the diameter of the bolt. As the bolt head is drilled, most of the time the bit will bite into the bolt head and spin the broken bolt out.
- Weld a piece of metal to the top of the bolt, to use as leverage when loosening.
- If the slot of a round-headed screw is stripped, file two flat edges in it. Then, it can be turned with an adjustable wrench. Or, use a hacksaw to file a new slot at a right angle to the existing one. Depending on the size of the fastener, using a Dremel tool or a die-grinder with a fiber wheel, carefully grind a large, deep slot in the head of the fastener, and before it cools, use a large screwdriver to remove it. The fastener is obviously not reusable at this point, but it can possibly save the difficulty of having to drill and tap a new hole through a hardened, broken-off fastener.
- Six-point sockets will grip better on hex nuts and bolts than 12-point sockets.
- Drill and tap the bolt to run another, smaller bolt down the center. A bit about half the diameter of the headless, stuck bolt is usually sufficient. Use a jam nut on the small bolt and lots of penetrating oil.
- If it is a stripped screw, either slotted or Phillips, try using a dab of valve grinding compound on the tip of the screwdriver. The valve grinding compound will help with friction to hold the tip onto the fastener when turning.
- Use a piece of tubing that fits in the bolt hole (OD) with the center (ID) the size of the drill bit. This will keep the drill bit centered in the bolt, when you use the EZ out.
- Where access allows, put a box end wrench over a stripped nut or hex bolt head, then use a center punch on the corners of the hex to spread the metal and wedge it in the wrench.
- If the bolt or stud breaks off below the surface, try this method. Using a high grade bolt of same size, grind off the threaded end until the bolt will fit into the hole and touch the broken bolt. Using an electric welder, clamp the "electrode" bolt in the stinger. This works best if someone is there to help you by turning the welder on and off. With the stinger bolt inserted into the broken bolt hole and firmly against the broken bolt, have the power turned on just long enough to fuse the stinger bolt to the broken one. You might want to practice this technique on the bench to get the power and timing right. Once they have cooled for a few minutes, but are still hot enough to burn skin, place a wrench on the slave bolt and turn them out.
- For removing stubborn Phillips-head screws, wet the tip of the screwdriver or screwdriver bit, a little bit of spit will do, and dip the bit into some valve grinding compound or abrasive cleanser like Comet or Ajax. Use enough to cover the tip of the screwdriver. The abrasive gives the tip of the screwdriver a little added "bite" and it's less likely to slip out of the screw.
- If you break off the head of the bolt, grind the remainder out with care using a TrueBite carbide bit and a high-speed rotary tool (Dremel MotoTool or some such) - see http://www.truebite.com/remove/ for details and instructions.
- With heating, bear in mind axles and other important structures may lose their strength if they are heated much above 300 degrees. If you have the oil and grease starting to smoke, then you are in the 300-plus degree range.
- When taking off cylinder head studs, look at the base. If you see erosion into the stud at the block surface, odds are pretty good you will break the stud.
- Whatever system you use, once you have a hold of the bolt, stud, or whatever, try rocking it forward and reverse a little at a time. If you can get it to move, it is more likely to come out. An older mechanic said always try to tighten a little before you loosen. Remember, if it moves, you are half way home. Also, brake fluid works great as a penetration oil.
- Use the largest cobalt drill bit (that almost just covers the top rim of the nut) to drill through the nut- parallel to the bolt- then used a chisel to turn/peel the nut off of the bolt.
- Tip of the day #33, Hotrodders Bulletin Board, December 10, 2005.
- Penetrating oil, Wikipedia, retrieved July 15, 2006.
- Stuck Bolts, ChevyTrucks.org, retrieved July 16, 2006.
- Removing Stuck Fasteners PumaRacing.co.uk, retrieved July 16, 2006.
- Loosening Stubborn Nuts, Bolts, and Screws Reader's Digest, retrieved July 21, 2006.