What's the difference between a tap and a die?

Taps and dies are both thread-cutting tools, but they create threads on different surfaces. A tap is used to cut internal threads inside a hole, such as in a nut or a cylinder head for spark plugs. A die, on the other hand, is used to cut external threads on a rod or bolt. For example, the Hanson High Carbon Steel (HCS) Metric Thread Plug Tap cuts threads inside a hole, while a die would be used to thread a rod of the same diameter.

What are the different types of taps, and when should I use each?

There are mainly three types of taps: taper, plug, and bottoming. Taper taps have a gradual taper that helps start the thread and are ideal for initial threading or when the hole goes all the way through the material. Plug taps have a less pronounced taper and are used after a taper tap to create a more complete thread. Bottoming taps have almost no taper and are used to cut threads to the very bottom of a blind hole. Vermont American offers various taper taps suitable for different applications.

What is a pipe tap, and how does it differ from a standard tap?

Pipe taps are designed to cut tapered threads, specifically National Pipe Taper (NPT) threads, which are used to create a tight seal in pipes and fittings. Unlike standard taps that cut straight threads, pipe taps create a conical thread that becomes tighter as the fitting is screwed in. For instance, the Hanson HCS Taper Pipe Tap is designed for creating these NPT threads in pipes, as opposed to standard threads for bolts and screws.

What do the markings on a tap or die mean (e.g., 1/4-20, M8 x 1.25)?

The markings on a tap or die indicate the thread size and pitch. For example, '1/4-20' means the tap or die is for a 1/4 inch diameter thread with 20 threads per inch (Unified National Coarse). 'M8 x 1.25' indicates a metric thread with an 8mm diameter and a thread pitch of 1.25mm. It's critical to match the tap or die to the correct fastener size and thread pitch to ensure proper fit and function.

What size drill bit should I use before tapping a hole?

The correct drill bit size is crucial for successful tapping. You need to use a drill bit that's slightly smaller than the tap's major diameter to allow the tap to cut the threads properly. The specific drill size is usually indicated on the tap packaging or in a tap drill chart. Some taps, like the Vermont American Pipe Tap, even have the drill size permanently marked on them. Always consult a tap drill chart or the tap manufacturer's recommendations for the correct size.

What is a tap socket, and when would I use one?

A tap socket is a specialized socket designed to hold and turn a tap, providing a secure and controlled grip. These are particularly useful when tapping in tight spaces or when needing consistent torque. Lisle offers tap sockets, such as the #9 Tap Socket, that provide a precise fit, improving leverage and reducing the risk of breaking the tap or damaging the threads.

What are some best practices for using taps and dies to avoid breakage?

To prevent breaking taps and dies, always use the correct cutting fluid or lubricant to reduce friction and heat. Start the tap or die straight and apply even pressure while turning, backing off occasionally to break chips. Avoid forcing the tool, as this can cause it to bind and break. Using a tap socket, like those from Lisle, can also help maintain alignment and control.

How do I re-thread a damaged spark plug hole?

Damaged spark plug holes can often be repaired using a rethread tap. These taps are designed to clean up or recut the existing threads in the cylinder head, allowing a new spark plug to be installed securely. The Lang M12 x 1.50 Rethread Tap is designed for this purpose, restoring damaged threads instead of cutting new ones. Always use cutting oil and work slowly to avoid damaging the cylinder head further.