How to Repair a Threading Tool

When working properly, tap and die sets cut threading for screws and nuts.

There are two types of threading tools included in a tap and die set. Taps cut threads inside a hole, as when threading inside a nut, and dies cut threads on the exterior of a piece of metal, such as threading on a bolt. If used improperly, taps and dies' cutting chamfers may become warped or bent, rendering them useless. Luckily, the tap or die that corresponds to the damaged piece can often be used to help straighten damaged cutting chamfers.

Things You'll Need

• Tap and die kit
• Die nut
• Bench vise
• Wrench

Instructions

Repairing Tap Chamfers

1. Measure the tap's thread size using a thread gauge, and match it to a corresponding die nut.

2. Tightly secure the tap in a bench vise so that it won't spin or swivel when you place pressure on it.

3. Begin threading the die nut onto the tap. Take extra care to ensure that the chamfers on the die and on the tap align properly as soon as you start threading the nut, otherwise the tap may become even more damaged.

4. Using a wrench, tighten the die nut to the end of the tap's chamfers. Because the nut will need to straighten the tap's chamfers, you may need to exert a lot of pressure on the nut. A long wrench provides more torque for this.

Repairing Die Chamfers

1. Secure the die in the bench vise. Clamping the die along the long axis so that the die's cutting channel is parallel to the floor will provide a stronger grip on the tool while allowing for more torque when turning the tap.

2. Gently start threading the intermediate tap that corresponds to the die's size. Be careful to align the die and the tap's chamfers so you don't end up cutting threads.

3. Once the tap has started threading with the die, attach the drive to the tap and continue turning until you reach the end of its chamfers. If the die's threads haven't been straightened all the way, swap a bottoming tap for the intermediate tap and continue until the die's chamfers have been straightened.

Tips & Warnings

• Replacement taps and dies are relatively inexpensive. It may be more cost effective to trash damaged hardware and purchase a new one rather than investing significant amounts of time on a repair.