Repair Damaged Nuts and Bolts

Restore stripped threads quickly with a rethreading kit

A rethreading kit is an important part of any automotive toolbox. Use it to restore stripped threads on old, rusty nuts and bolts when you don't have time to search the stores for a replacement.

By the DIY experts of The Family Handyman Magazine

Start by finding the thread count

No matter how careful you are when you reinstall old rusty nuts and bolts, someday you're going to strip some threads. Of course it will happen on a critical bolt, on a Sunday night when all the stores are closed. That's when a thread restoration kit pays for itself. A full set (metric and SAE) will quickly put irreplaceable and hard-to-find nuts and bolts back into service. The rethreading tools look like traditional taps and dies. But instead of cutting new threads, they reshape them to original condition.

To restore bolt threads, start by finding the thread count (SAE) or pitch (metric). Hold the thread file against the bolt threads until you find the size that matches. Clamp the bolt in a vise, engage the thread file grooves with the bolt threads and push the file (Photo 1). That “resets” the threads enough so you can screw on a rethreading die (apply a few drops of oil first). Use a rethreading tap to restore threads on nuts or threaded engine component holes. Don't try to rethread the entire bolt, hole or nut in one operation. Insert the rethreading tap or die and rotate a few turns, then back it off a full turn. That will dislodge the debris from the teeth.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Rags
  • Vise
  • Wrench set

You'll need a thread restoration kit from an auto parts store.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

  • Lubricating oil