Typically caused by the inevitable rust and corrosion that occurs inside a screw hole, a stuck screw can be an incredibly frustrating thing to work with. Not only can it slow a project down, but it can throw a wet wool blanket over anybody's good mood. This corrosion effectively locks a screw into place and removing the thing can potentially destroy the screw itself or, worse yet, the material it's embedded in. Fortunately, though, there are few sure-fire methods that will help you remove a stuck screw with relative ease and minimal annoyance.
Before beginning to beat-up your screw, though, please be sure you have the correct size and type of screwdriver; the wrong one can strip the screw-head making it incredibly more difficult to remove and virtually impossible without destroying it altogether.
1. Chemical Warfare:
The first and least invasive method of stuck-screw extraction is the use a little chemical manipulation. While that may sound complicated, some pretty everyday "solutions" should dissolve the corrosion that's binding your screw. For instance, lemon juice, hydrogen peroxide and even a refreshing cola beverage can breakup corrosion and release a stuck screw. You may even go all out and reach for some rust remover at the grocery, home or hardware store (though this is both more aggressive and more expensive).
Although this technique is typically the most gentle way to release a stuck screw, you must be careful not to stain or damage your material. Damage may occur where an anti-corrosive is too potent or is left soaking for too long.
In either case, your anti-corrosive solution of choice should be left to soak for a few minutes. To the best of your ability apply the solution inside the screw-hole; tapping the screw-head while applying will help the anti-corrosive penetrate deeper into the screw-hole (and will therefore loosen or release more of the screw). The more surface area you can contact with the solution, the easier the screw will come free.
After adequate soaking, attempt to remove the screw. If the screw will not loosen, attempt to tighten it (you can utilize the tightening technique throughout most of the below methods). If the screw will move in either direction (even the tighter direction) the movement should break the corrosion and, effectively, set it free. If the screw still won't budge, it's time for our next method.
2. Brute Force:
This method involves muscle - good-old-fashioned, gettin-it-done muscle (and a tool or two to enhance your human strength). First, if you can get a grip on the screw-head, try to grab it with pliers or vice grips. If you can get hold of it, you may be able to turn it with this added leverage. If you can't get hold of it, insert the screwdriver into the screw-head, lock the pliers or grips onto the shaft of the screwdriver and, while pushing down it, try to turn it again. The downward pressure form the screwdriver and the turning leverage from the grips may break the screw loose.
If this doesn't work, try hitting the top of the screwdriver (not so aggressively that you destroy the tip of it, but enough to let that screw know you're there). Ideally, the impact will bust-up some corrosion and release the screw. If you can manage it, also try hitting the screwdriver while turning it - this combination of impact and rotation will often force a screw loose. - Be careful, though, not to strip the screw-head.
3. Temperature Tampering:
Before using extreme temperatures on your stuck screw, be sure the material the screw is stuck in can handle such fluctuations. I you heat it up, don't use lubricating oils as they are flammable and may catch fire. Extreme temperatures may also burn you, so please, be cautious and wear appropriate safety gear.
The first thing to try is heat. Using a butane or propane torch, a soldering iron, a heat gun or even a glue gun (without glue, of course) you can get that screw nice and hot. The heat will expand the screw, break the corrosion and should allow you to joggle it loose.
If your material can not or should not be exposed to high-heat, chilling the screw, although, less effective, may also get the thing loose. Allow ice to set on the screw (place ice in a plastic bag to avoid too much water permeation). Dry ice is more effective than "regular" ice. When the screw has become good and freezing cold, try turning it in both directions.
Heat and cold cycles can be repeated for better results.
If the screw absolutely must come out and none of the previous methods have worked, you may have to destroy it. Of course, destroying the screw is a last resort and these methods are typically reserved for the end of the line. When employing the destruction method, be careful to keep the screw-hole intact.
First, position a small chisel or steel punch just slightly off center in the screw-head. Repeatedly strike the top of the chisel or punch with a hammer. Strike with counter-clockwise pressure. Several impacts of this nature should separate the screw from the corrosion and loosen it for removal.
You may also get funky with your power drill and attempt to drill out the stuck screw. This will typically destroy the screw-head altogether but you may be able to get it moving before the head is useless. - Keeping your drill bit firm and dead-center on the screw-head, attempt to reverse the screw from the hole. Be careful not to lose your mark and, in doing, mar the surrounding material. If you can get some of the screw to release but you have destroyed the screw-head, grab whatever portion of the screw you can with your pliers or grips and twist it out.
5. Total Annihilation (the Screw Extractor):
Of course, the screw-annihilation route is a last resort, but, where you're stuck-screw is really dang stuck or where any screw has lost its thread, head or head-slots, it may be impossible to remove without a screw extractor.
A screw extractor is designed to drive into a screw's body, grab it, twist it and remove it. The thing is a pretty brilliant little device that runs only about $10 (give or take). Though it's built to fastened to a T-handle, the screw extractor's square head and reverse tapered cutting threads can work their magic just as well with an adjustable wrench or pair of vice grips.
First, using a power drill and the smallest drill bit you've got, drill a pilot hole into the center of the stuck-screw. Expanding the pilot hole with slightly larger bits, the final size of your pilot hole will vary depending upon the size of the screw extractor being used. With your grips, pliers or T-handle, insert the extractor into the pilot hole. Tap the top of the extractor with a hammer to ensure it's secured into the pilot hole and, while pushing downward, turn the extractor counter-clockwise (or, to the left). Be careful as you push and twist, though, because although an extractor is typically fabricated of superior grade steel, the extractor may break inside the pilot hole if pushed to aggressively. Ultimately, though, the reverse threads on the extractor will dig into the interior of stuck-screw, release the corrosion and, most importantly, remove the screw.