11 Tricks For Removing Rounded-Off Bolts
We have all had it happen. You are turning a wrench and then BAM, the head of the bolt rounds off, the wrench slips, and you bust your knuckles on the edge of something sharp. It never fails; there is always a sharp edge next to a rounded bolt waiting for your tender knuckles. Not only are you cringing in pain, but now you have a problem: that was the last bolt holding whatever part you have to remove to the car. It has to be removed, but some methods are better than others to get the job done. Here are some tips and tricks to removing rounded-off bolts.
Rounded-Off Bolt Removal Techniques
First things first, you should always lube up your nuts and bolts before trying to remove them, especially if they are rusty or have been in place for many years. At the first hint of a problem, stop, grab some penetrating fluid and soak it. Let it sit for 5-10 minutes and come back to it. The times you spend waiting will save you in the long run. Another lubrication trick is to heat the bolt up and then melt wax onto it. The heat wicks the wax into the threads and many times, the bolts will come right out. Just be careful with the heat source so you don’t accidently melt anything or start a fire.
Use Anti-Cam Out Fluid
If you are working with a screw, particularly a Phillips-type, apply a drop of anti-cam out fluid to the head at the first hint of slippage. This will help hold the screwdriver bit in place while you apply pressure and turn. Stripping a screw head stinks.
Use A Screwdriver
Let’s say that the rounded-off bolts or screws are spinning, but not coming out because the threads are damaged. A quick way to get the bolt back to the good part of the threads is to wedge a small screwdriver or flat blade between the part and the bolt, nut, or screw head. Apply pressure to push the bolt out and unthread it. This works miracles.
If the head of the bolt or nut is chewed up and rounded, there are several specialty sockets & wrenches available to help. Traditional bolt extractor sockets have reverse-cut spiral teeth that grip the head of the nut or bolt while you turn the ratchet. Depending on how gnarled the damage fastener is you may have to try different size extractors to get the best grip. Luckily NAPA has several unique designs that can get you out a jamb.
This Carlyle Tools dual action quick self-adjusting wrench works on fasteners from 5/16 in to 1 1/4 in (8mm – 32mm). Check out how it works in the video below:
If you don’t have a specialty tool or are on the side of the road, try a slightly smaller socket or wrench. It is a good idea to keep both metric and SAE sockets in your car regardless of what type of bolts are used. A 12mm socket is just slightly smaller than a 1/2”, so you can tap it on with a hammer, add some lube and you might be home free. If you go this route make sure to inspect the socket afterwards for any cracks or damage caused by forced it over the damaged fastener.
If the bolt is just completely wasted, you need some VISE-GRIP locking pliers. Locking pliers come in many sizes, so you should be able to grab a pair that will match up. Stay away from needle-nose and flat-jaw locking pliers though, as these won’t be able to get the grip you need. Instead, use the round section of the jaws. If the locking pliers can’t get a good grip, grab a file and flatten two opposite sides of the stripped bolt or nut. That will give the locking pliers a better surface to hold.
If you still can’t get it loose, grab a propane torch and put some heat on the part. You can try heating up the surrounding threads or concentrate on the bolt. Once it is good and hot, hit it with some penetrating oil. This will shock the hot metal, breaking the thread’s grip, allowing you to free the bolt.
Cut A Slot
Still can’t get it? Grab the rotary tool, die grinder or angle grinder and cut a slot in the center of the head. This lets you use a flat blade screwdriver. If the bolt is stuck, a simple impact screwdriver will work great to give the shock the bolt needs to break free. Just make sure to use proper eye protection while cutting.
Weld A Nut
If you have the equipment you can try to weld a new nut to the head of the old one. This the last resort for blind fasteners (where is the not a nut on the other side) before you have to drill it out. The heat from the welding process may also help break free the seized threads.
Cut It Off
Sometimes, you just have to cut out rounded-off bolts. An angle grinder with a cut-off wheel works best, but a reciprocating saw works great too. This is used when there is a nut and a bolt. No power tools available? For stripped nuts you can use a nut cracker to physically split the nut in half. Just position the nut cracker over the nut and tighten the bolt.
Drill It Out
If you can’t cut it, you have to drill it out. Use a center punch to get as close to the centerline of the bolt. Use the smallest bit you can to start the hole, and then slowly work your way up. Eventually, you will get to the edge of the threads and the bolt will come out. Bolt extractors have a bad habit of breaking in the bolt, so be careful if you decide to use one. Don’t cheap out; you want good extractors, not cheapies that break. Removing a broken bolt extractor is a whole new level of frustration.
Using these tips, you should be able to get those rounded-off bolts out in no time.
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Jefferson Bryant View All
A life-long gearhead, Jefferson Bryant spends more time in the shop than anywhere else. His career began in the car audio industry as a shop manager, eventually working his way into a position at Rockford Fosgate as a product designer. In 2003, he began writing tech articles for magazines, and has been working as an automotive journalist ever since. His work has been featured in Car Craft, Hot Rod, Rod & Custom, Truckin’, Mopar Muscle, and many more. Jefferson has also written 4 books and produced countless videos. Jefferson operates Red Dirt Rodz, his personal garage studio, where all of his magazine articles and tech videos are produced.
For the Phillips or Reed & Prince screws that are slightly rounded out, you can often get enough grip to turn the screw if you put some Honing Compound on the screwdriver tip. Saving the “grit” in the bottom of your automatic transmission pan also works like the honing compound. Just put it in a jar when the pan is down, for future use.
What is the name/product number of the Gearwrench you mention in article? I need one for a 17mm nut that is rounding.
The wrench is a universal spline drive (Part #: APX 86126) found in this set: https://www.napaonline.com/en/p/APA86126 For the 17mm only (Part #: APX 86117) you need this: https://www.napaonline.com/en/p/APA86117