Things You'll Need
Locking vise grip pliers
Open-end box wrench
Stiff wire brush
Few things are more frustrating than a bolt head that's been stripped or rounded off. Torx head bolts are well known for their resistance to stripping, but even they are not immune. Over time, moisture, dirt and debris can build up and weaken the head or rust the threads. Once a bolt head has been stripped, it's time to take a step back and evaluate your options. Further attempts to remove the bolt with a Torx wrench will only serve to further remove any material that is remaining.
Clean and Lubricate the Bolt
Spray down the bolt head and any portion of the threads you can gain access to with a penetrating oil. In most cases where a bolt has become stripped, it is due to threads that have become locked from rust or corrosion. Penetrating oil will remove some of this rust and lubricate the threads.
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Allow the penetrating oil to seep around the threads of the bolt, which takes about 30 minutes.
Use a stiff wire brush to brush out any rust or debris on the surface of the bolt head.
Reshape the Bolt Head
Use an angle grinder or rotary tool to grind the round outside edge of the bolt flat on two opposing sides so that you have two parallel gripping surfaces.
Grasp the bolt firmly by locking a pair of vise grip pliers onto the now flat sides of the bolt and attempt to loosen it. If you are unable to loosen the bolt using locking vise grip pliers, use an open-end box wrench applied to the flat portions of the bolt.
Remove additional material with an angle grinder or rotary tool from the flattened sides of the bolt if necessary to achieve a tight fit with the open-end box wrench. Take care to work slowly, removing a tiny bit at a time and test fit your wrench often until a tight fit is achieved.
Turn the wrench counterclockwise for standard threads to remove the bolt.
Slide a breaker bar over the end of the wrench to provide additional leverage if necessary.
If you can do it safely, apply heat to the bolt to help loosen the threads.