Repair and Construction

Broken Screw Extraction

by: Bob Dill - December 1987

Do you use a stud and plate to hold your plank on?  Do feel like a frustrated dentist trying to dig broken screws out of your plank and hull with a hand drill?  If so, Chuck Bond from Westford, VT (US 4031) has found the answer to one of your least enjoyable tasks.

Chuck figured out that he could make something like a miniature hole saw with a short piece of thin walled metal tubing with the right internal diameter.  The ID should be slightly larger than the screw shank.  Chuck has used various things as tube: broken radio aerials, thin brass tube, copper pipe, or what ever was handy at the time.  He felt radio aerials tube worked best.  Another alternative is to machine a drill especially for the task as shown below.

Small teeth or slots are filed into the bottom edge to help it cut.  This hollow drill is pulled out of the hole frequently to remove the sawdust.  The center hole should also be kept clear.  The teeth can be set up for left hand (counter clockwise) drilling.  The screw will usually back out more quickly when drilled this way (with the drill in reverse).

After the screw is out, there is usually a little bit of its original hole at the bottom of the new hole to center the new screw. Fill the hole with epoxy, put in the new screw and make sure the plate is in its proper position.  If the screw breaks again the process works just as well with an epoxy potted screw as a screw in wood.

The following drawing gives approximate dimensions for one of these drills made on a lathe from 3/8 drill rod.  Drill rod can be hardened easily although being hard isn't all that important.  This drill is designed for the #8 stainless screw Sarns sends with stud and plate sets.

Screws usually won't break unless they get loose first or unless you hit something (when they should break).  When they are tight they share the load.  When they are loose they all get to share the load; a couple at a time until they all break and you get dumped very abruptly on the ice (usually just past the windward mark).  Put them in with epoxy and check them periodically to make sure they stay tight.

screw extractor