Taps and Dies for Threading

Taps and Dies

• Taps are tools that cut threads into a hole, allowing a bolt to be screwed into it.
• Taps are typically made of high-speed steel with long channels ground into the sides, leaving gaps in the threads.
• These channels allow chips to break free and be ejected as the tap turns into a hole.

Types of Taps

• Plug taps: the most common type, suitable for general purposes, with a slight taper, allowing for threading almost to the bottom of a blind hole.
• Taper taps: start narrow and then taper to a full thread width, making it easy to start when threading into a hole.
• Bottoming taps: for forming threads in the full length of a blind hole, recommended to use a taper or plug tap first to form the initial thread.

Drill Bit Size and Thread Count

• For every bolt, there is a corresponding tap of the matching diameter and number of threads per inch.
• Similarly, for each tap, there is a corresponding drill bit size that should be used to drill the initial hole.
• These relationships can be found on the packaging or through a quick internet search.

Using a Tap

• Secure the piece to be tapped using a vise to avoid breaking the tap.
• Use a tap wrench to turn the tap, inserting the square end of the tap into the adjustable jaws.
• Align the hole directly below or in front of you, and apply slight pressure to the tap while turning the wrench.
• After every full turn of the tap, give it a half turn in reverse to break the chips off and clean out the thread.

Dies

• A die is the inverse of a tap, cutting threads onto the outside diameter of a rod.
• The rod material will dictate which die to use, and the rod should be prepared by filing or grinding a bevel onto the end.
• Use a die stock to hold the die securely, and spin the die onto the rod while keeping the rod straight.

Threading with a Die

• Align the die with the rod, apply pressure, and turn it onto the rod.
• Once the initial threads have been formed, remove pressure and continue turning, remembering to give it a backward turn once every revolution to break the chips.
• Test the threaded rod once it has been cut to the desired length.