Why do Bolts Break?

Broken bolts causing downtime have long been the source of frustration.  Collectively, a broken bolt can cost hundreds of thousands of dollars between repairing the machine, scrapping parts, employee pay, and money lost on sales loss.  So why do bolts break?

Using the wrong Bolt

In some applications, the bolt may break because it is too long.  This can cause the bolt to snap in half.  Ensuring that your bolt is a secure fit can reduce the risk of bolt breakage.  

It’s not tight enough

The bolt may be loose as stated by Proven Productivity, fatigue failure, one of the causes is improper tightening of a bolt.

Fractured bolts

The bolt may be fractured which can be caused by extreme temperature changes or stress from movement of parts.  Thomas refers to this as “Bolt Locking” caused by large amounts of vibration which results in uneven stress on bolts can cause breakage.

The threads become stripped

The top of the bolt twists off, most often the result of tightening the bolt too tightly or using the improper tool for tightening the bolt.

The top of the bolt breaks off

As proven productivity states, bolt failure may happen as a result of fatigue failure.  This can be a result of not tightening the bolt properly causing stress and eventual failure.

What can you do when a bolt breaks?

Chances are if you have visited online forums or experienced broken bolts in a shop you know there are a lot of interesting tricks to removing broken, sheared off, stripped, and snapped bolts, screws, and other fasteners.

Ideally, a tap buster will remove your broken tooling in no time.  However these machines are expensive and your company may not invest in a tap zapper if you are not breaking off bolts, drills, and taps on a regular basis.  You may be able to find a shop that offers broken bolt removal service and that investment is well worth your time considering most of these suggestions also take a majority of a day to remove.

Penetrating fluids – this trick can help remove a broken fastener especially if you soak the part and wrap it to avoid evaporation.  This method is designed to crack the broken fastener at the last point of contact which may result in a bigger mess.

Depending on your situation, you may be able to improvise using hand tools.  Sawing or filing may easily remove the fastener as on a larger hex bolt.  Specialty stud removal tools and left-hand drill bits are designed to remove these broken bolts but they may not be as effective as advertised.

Are Metal Disintegrators EDM machines?

It may not be common knowledge, the specialty tool developed just for removing broken bolts was developed in the early 1940s.  If you have heard of a tap zapper or spark eroder, these are slang terms for the metal disintegrator. This machine can remove broken bolts in minutes.  The technology basis for this machine is EDM which has evolved to include many subcategories over the years as this technology has improved.

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