Rick's Free Auto Repair Advice

Remove stripped bolt

Remove stripped bolt — How-to

This post covers how to remove a stripped bolt head but the tips also apply to a stripped nut. I’ve written another post on how to remove a stripped screw. Find that post here.

Why the bolt stripped — most common mistakes

Using the wrong tool

When it comes to rusted bolts and rusted nuts, the easiest way to strip the fastener is to use the wrong wrench or socket. If you have any inkling that the bolt or nut might not come off easily, DO NOT USE a 12-point socket or wrench.

You’ll find 12-point sockets and wrenches in most 6 point versus 12 point socketinexpensive socket and wrench sets. The only advantage to a 12-point socket is that they require less maneuvering to fit onto the bolt. For example, if a 6-point socket doesn’t fit onto the hex head of the bolt or nut, you may have to rotate the tool up to 60° to get the flats matched up. You only have to rotate a 12-point socket or wrench 30°.

But, 12-point sockets and wrenches only grip the hex head at the outer tips of the hex flats, while a 6 point versus 12 point wrench6-point socket grabs the tip and the flank of the bolt head. You always stand a better chance of removing a bolt or nut with a 6-point socket or wrench.

Not using a rust penetrant first

The second most common mistake DIYers make that results in a stripped bolt is not applying a rust penetrant first before applying force to the bolt or nut. Think of rust as a type of glue and a rust penetrant as both a solvent and a lubricant. So what’s a good rust penetrant? NOT WD-40! Yes, you read that correctly. WD-40 is a great general purpose lubricant. It has a solvent base and a light weight oil as the lubricant. In some cases, it can penetrate light rust. But it’s not the best rust penetrant. In fact, WD-40 makes a rust penetrant for this exact purpose. It’s called Rust Specialist and it’s specifically designed to free us rusted fasteners.

There are other really good rust penetrants like PB Blaster, Freeze-Off and Kroil.

Best rust penetrants

Best rust penetrants

Best rust penetrants

How to remove a stripped bolt or stripped nut

Step #1 Apply rust penetrant to the stripped nut

As I mentioned above, the first step is to soak the stripped bolt or stripped spray with rust penetrantnut with a rust penetrant.

Step #2 Shock the stripped bolt with vibration

Next, shock the stripped bolt with vibrations to help crack the rust and allow it to penetrate into the threads. If you have an air compressor and an air impact gun, use that to vibrate the area all around the stripped nut or bolt. This is a really important step that can greatly reduce the amount of time and effort required to remove the stripped bolt.

impact hammer bit

Step #2 Use a bolt extraction socket

A bolt extraction socket is a reverse threaded spiral that cuts into the hex head while you turn the socket counter-clockwise. The harder you apply extraction socketeverse force, the more the socket grips the bolt head. Simply pound the socket over the bolt head and attach a ratchet. Set in reverse and turn counter-clockwise.

If you don’t have bolt extraction sockets, try using an SAE (fractional) socket on a metric bolt head or vice versa. You may have to pound it onto the bolt head to make it fit.

Still can’t remove the stripped bolt? Time to get ugly

Buy a Go-2 socket

If you have the time and money to order specialty tools, try a Go-2 socket. go2 socketSimply fit it over the stripped bolt and tighten the screw to wedge the bolt head into the socket. Then use your ratchet to unscrew the bolt.

Buy a nut cracker

This one doesn’t work on a bolt head but works fairly well on a nut. The nut cracker tightens around the hex head and the internal chisel splits the nut. Just tighten with a socket/ratchet or wrench until you hear a “snap.” That’s the sound of the nut splitting.

nut cracker

Use a cut off wheel

This method only works on stripped nuts. But, if the other methods haven’t worked, use a cut-off wheel to cut straight down the bolt threads on one side. In many cases you don’t even have to cut all the way through the nut before it frees up

Should you use heat to remove a stripped bolt?

I’m not a big fan of heat. First, most people misuse it and head the bolt until it’s cherry red. That’s overkill. The entire point of heating the bolt is to make it expand and break the rust bonds. If you’re going to use heat, first make sure there are no flammable materials nearby or in the bolted assembly.

Then heat the stripped bolt head or nut until it starts to smoke. Then immediately squirt cold water on it. Don’t try to turn the hot bolt. Why? Because you just make it expand. It’s engaged with the threads even tighter than when it was cold. Squirting the bolt head with water makes it contract, which will actually free it up from the threads, and that’s what you want.

©, 2020 Rick Muscoplat



Posted on by Rick Muscoplat

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