Workshop Hints
Removing broken screws

The British Horological Institute has provided a digest based on e-mails sent to the Clock/Clockers mailing lists on the Internet. The information here does not necessarily indicate a method approved by the BHI, we are only publishing this digest so that others can decide for themselves whether the methods listed below will suit them.

Based on E-mails from: Jeanne Barndt, Colin Fergusson, David Goodman, Bill Murray, Donn Lathrop.

One regular problem is screw heads breaking off, and the thread is still left in the workpiece. This can be very annoying and can, if you don't know the tricks of the trade, be time consuming.

Here are a couple of tips on removing the screw body.

• If the screw is reasonably loose, gently, using a sharp scriber,put the point of the scriber on the broken screw and gently try to turn the screw by tapping the end of the scriber with a small hammer. The scriber point will dig into the broken screw and if it is reasonably loose it will start to turn.
• If the screw is in tight. Drill a small hole down the centre of the broken screw. The hole should be large enough to put the tang of a small file down it, but small enough so that it does not break into the threads. When the hole has been drilled, select a suitable old file and gently tap the tang end into the drilled hole using a small hammer. The tang should now be gripping the screw, and turning the file will turn the screw.
• Another way is to purchase a set of left hand twist drills. Drill a small pilot hole first and then use the left hand twist drill.As you use these drills to drill into the broken screw it will tend to try and unscrew the broken screw rather than drill through.
• If the screw is large enough, there is a commercial product available called 'Easyouts'. these act in the same fashion as the file tang used in method 2.
• Ferrous material, such as broken screws, can be removed from brass items by soaking the parts in a saturated solution of Alum. Alum can be obtained from chemists, as it is used to treat bed-sores. The process is slow, though it can be speeded up by heating the solution. Clearly, it is necessary to remove any ferrous parts other than the "target" piece.The brass will not be marked.

I hope you never have to use these methods, but they do work in most cases. If all else fails, you have to drill the screw out and then re-tap.

Index of Hints and Tips