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Releasing a sheared off bolt by welding



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What is the issue?
Bolts and nuts, like most fastenings, have a tendency to seize on boats due to the challenging seagoing environment. Apply just a touch too much pressure and the tension suddenly becomes soft or rubbery, and you are either breaking the bolt or stripping the threads. Most likely the former leaving a seized and often inaccessible bolt shaft sheared off.

Why address this?
A sheared off bolt can halt a project, cause frustration and cost money.

How to address this?
This approach assumes you know how to weld or can get someone to do this for you. A MIG welder is preferred for this task as an arc weld creates a lot of slag which gets included in the weld. However, the primary purposes here is to get the sheared off stud out and either welder will do the job perfectly well.

The easiest approach to removing a stuck bolt is to get a nut of the same size and place it over the sheered head. A neat trick is to superglue it in place first so it sits tight for the weld. Then weld the nut to the head of the sheared off stud. Once it has cooled get a spanner on the nut and turn it out – see releasing seized nuts and bolts.

This approach is almost guaranteed to remove even the most stubborn bolt because the bulk of the work is carried out by the welding process itself. The heating action of the weld breaks the molecular bond fixing the bolt or screw threads. In addition to this, the heating and cooling action fractionally expands the metals at different rates aiding separation.



Another approach, if there is little space around the nut or in an area that may get damaged, is to weld a smaller bolt onto the head of the stud as illustrated below. As above, the smaller bolt is welded in to support a wrench working the stud out. Here are the steps:

  • 1/ Find a smaller short but solid bolt.

  • 2/ File or grind the sheared off bolt until it is flat and clean.

  • 3/ Locate and mark the sheared off bolt's centre point with a centre-punch.

  • 4/ Drilling in a hole that your selected bolt comfortably sits in. This need not be very deep, a three to four-millimetre seat is perfectly adequate.

  • 5/ Superglue the bolt to get it to sit right.

  • 6/ Weld the bolt with the lightest rod that will stick to the shaft.

  • 7/ Cool for five to ten minutes then get a spanner or adjustable wrench on the smaller bolt head.

  • 8/ Nudge it back and forth with the wrench to work it free

  • 9/ Turn the bolt out when it frees up.


With thanks to:
Bernard Harpur, Co. Wexford, Ireland




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