Taps and dies are metal threading tools that work hand-in-hand. Taps form internal threads inside a hole or nut while dies carve external threads on a cylindrical rod. Taps and dies can also serve the purpose of rethreading when threads are worn out or for tidying up existing threads following a plating procedure.
Types of Taps
- Straight Flute Tap: Also known as a hand tap. It has straight flutes and is used for general-purpose threading in a wide range of materials. It requires a tap wrench or handle for operation.
- Spiral Flute Tap: Also known as a gun tap. This tap has flutes that twist around the tap body, allowing chips to be pulled out of the hole as it threads. It is suitable for threading deep holes and works well with materials that produce long chips, such as aluminum and brass.
- Spiral Point Tap: It features a pointed end with spiral flutes and is designed for threading through holes. The spiral point pushes chips forward, away from the cutting edges, making it effective for materials that tend to produce stringy chips like steel.
- Spiral Flute Bottoming Tap: This tap has a shallow lead and a continuous cutting edge, allowing it to reach the bottom of blind holes. It is used for threading holes that don't extend through the material.
- Pipe Tap: Specifically designed for threading pipe threads, these taps have tapered flutes that help create tight, leak-free connections. They are commonly used with materials like steel, copper, and plastic pipes.
- Forming Tap: Instead of cutting threads, a forming tap works by displacing the material to create threads. It is used with ductile materials like aluminum, copper, and stainless steel, and produces threads with improved strength and surface finish.
- Interrupted Thread Tap: This tap is used for threading in holes with interruptions, such as keyways or cross-holes. It has a modified thread profile that allows it to pass through the interruptions while still forming threads.
These are just a few examples of tap types commonly used for threading. It's important to select the appropriate tap based on the material, hole type, and specific threading requirements to achieve accurate and efficient results.
Taper tap, bottom tap, and plug tap are different types of hand taps used for threading holes in metal and other materials. Each tap has a distinct design and purpose, allowing them to perform specific tasks in the tapping process. Here are the main differences between them:
- Taper Tap:
- Also known as a starting tap or roughing tap.
- Taper taps have a gradual and extended chamfer at the tip, which helps them start threading easily and align with the hole.
- They are used to create the starting threads in a hole and are generally the first tap used in the tapping process.
- Taper taps produce threads with a more gradual pitch and are useful for difficult-to-machine materials or when alignment is critical.
- They are not suitable for tapping to the bottom of a blind hole because the extended chamfer prevents them from reaching the full depth.
- Bottom Tap:
- Also called a plug-bottom tap or finishing tap.
- Bottom taps have a very short chamfer at the tip compared to taper taps.
- They are used to finish threading at the bottom of a blind hole, where the tap needs to reach the full depth of the hole.
- Bottom taps are used after the taper tap and help to accurately complete the threading process at the bottom of the hole.
- Their short chamfer design prevents over-threading and ensures the threads stop at the desired depth.
- Plug Tap:
- Also known as a middle tap or intermediate tap.
- Plug taps have a chamfer length that is in between that of taper and bottom taps.
- They are the most common type of tap and are used for general threading tasks in through holes (holes that go completely through the material).
- Plug taps are suitable for most threading applications and are commonly used in various industries.
- They offer a balance between starting ease (like a taper tap) and the ability to reach the full depth (like a bottom tap) in through holes.
Common materials used to make tap and dies include:
- High-Speed Steel (HSS): High-speed steel is a popular choice for tap and dies due to its excellent combination of hardness and heat resistance. HSS tools can withstand the high temperatures generated during the cutting process without losing their hardness, making them suitable for use in various materials.
- Carbon Steel: Carbon steel is also used to make tap and dies, although it is not as durable as high-speed steel. It is a more economical option but may not be as effective in cutting hard materials or under heavy use.
- Cobalt Steel: Cobalt steel, an alloy of HSS with a small amount of cobalt, offers improved heat resistance and is often used in applications where the tool will encounter high temperatures or require extended tool life.
- Powdered Metallurgy Steels: These are advanced materials made by sintering metal powders under high heat and pressure. Powdered metallurgy steels offer excellent wear resistance and toughness, making them suitable for demanding threading tasks.
The choice of material depends on factors such as the type of threading operation, the material being threaded, and the expected tool life. High-speed steel is the most common material due to its balance of performance and cost, but more specialized applications may call for other materials with specific properties.