13 Different Types of Thread Taps

Taps make threaded holes so that they’re ready for fasteners like screws and bolts to be inserted or tightened with a drill or appropriate hand tool. Turning the tap by hand creates threads inside pre-drilled holes. They’re found in manufacturing parts, like vehicles and structures, and they’re also in flat-packed furniture—handy for those putting it together as they won’t have to manually make these holes. 

Thread Tap Types

There are tons of different types of thread taps with many varying endpoints, tapers, and flutings. Let’s look at 13 of them to help you decide on the right one for your needs—because, let’s face it, knowing which one to use is a total shot in the dark.

Hand Taps

Hand taps are multifunctional and work either by hand or with a power tool. They’re used for machine tapping in general and most materials with blind or through holes. These have straight flutes used in shallow blind or through holes. A standard hand tap set has three separate types, which we’ll discuss below. 

Plug Taps

A plug tap has a five-thread cutting chamfer that slowly cuts away material to create the thread, starting with the smaller diameter. They’re used when there is enough space at a blind hole’s bottom part, or to make through-holes. They make a more complete set of threads compared to taper taps, but aren’t as well suited to finishing threads in blind-holes as bottoming taps.

Taper Taps

These have nine-thread chamfers and the smallest diameter of any hand taps. Taper taps are typically the starting point for blind- or through-hole applications. One of their biggest advantages is they clear out most of the material early in the process. They shouldn’t be used for finishing the bottom of blind holes since they can leave incomplete threads.

Bottoming Taps

A bottoming tap has the smallest thread chamfer (1.5 inches). It’s used to finish the end of a blind hole since it can get all the way to the bottom (unlike plug and taper), but isn’t good at removing most of the material from the hole (that’s what the other two are for).

Pipe Tap

Pipe taps carve threads for pipes internally for pressure-tight joints. Some pipe taps are made for hydraulic and gas purposes, and others for mechanical joints and hose couplings. They have to be done more carefully than other types because they’re designed to mechanically seal a joint to add pressure and prevent leaks.

Spiral Flute Tap

The spiral flute tap has flutes wrapped around the axis in a spiral (helical) formation, making their cutting edge weaker than a hand tap’s. They’re most often used to tap thread into blind-holes and then pull the chippings back out of the hole.

Gas Tap

Gas taps are compliant with specifications used in gas and hydraulic systems. They’re a form of pipe tap used for cutting deep threads, and either have one- or two-thread chamfers suitable for conical and cylindrical-shaped holes.

Machine Tap

The growing use of machinery in manufacturing has meant an increase in machine taps, too. These have to be durable and particularly resistant to wear. Automated machining processes (like CNC) use these taps to create both blind holes and through holes on hard materials, where spiral flute taps won’t be strong enough. Sometimes their cutting end is coated with titanium nitride (shown in the below image) to give it more wear resistance and increase its lifespan.

Thread-Forming Tap

Also known as fluteless taps or rolled threads, these taps don’t actually cut threads; they cold-form them instead, during which the metal isn’t cut, but moved away before being compressed into position. No chips are formed in the process, meaning you don’t have to remove any. These taps make stronger threads that are less likely to break. 

We suggest using form taps instead of cutting taps whenever you can, as long as the material isn’t too hard. Lots of people think that these are only good for soft materials like aluminum, but they work with any material with a hardness of 36 HRC (or 340 BHN). That covers a bunch of materials, including a lot of steel types.

Master Tap

A master tap is used in many industries. They’re known for their universal ability and are typically used to cut clean threads in hard, strong materials. They’re not that dissimilar to taper taps but have 7–10 flutes (as opposed to a taper tap’s 3–7) and more cutting faces.

Combined Drill and Tap

A combined drill and tap lets the user drill the hole and tap threads all at once without having to switch tools. This saves both time and money on production drilling jobs. It’s helical flute-shaped and works on a host of materials and metals, like iron and brass.

Solid Carbide Tap

Solid carbide taps are made of composite material and last a long time in all sorts of environments. They’re very hard and wear-resistant so are used on harder materials, including sintered, ultra-fine tungsten carbides.

Extension Tap

Extension taps are similar to hand taps. Their long shanks make them useful for accessing hard-to-reach holes, like a pulley hub.

Spiral Point Tap

These taps are strong and made to work faster than regular taps on hard materials, and don’t need as much power, either. They make shallow grooves that can remove more metal in one go. Some feel they are similar to straight flute taps since they share the same general shape, but they have different cutting faces.

Stay Bolt Tap

A stay bolt tap is around 15-20 inches long. It’s designed to cut threads in drilled holes for threaded machine screws or threaded bolts to be screwed in, in the exact diameter of the stay bolt nut. They were commonly used in installing and repairing fireboxes in steam locomotives.

Interrupted Thread Tap

This type of tap only has a tooth for every other thread. It’s designed to provide better chip extraction. Removing every other tooth helps with breaking up the chips. It also gives more room, both for the chip to clear out and the lubricant to enter.

Thread Tap Type—Summary

For ease of reference, we’ve made the below table so you can quickly see the main differences between these types of thread taps (in the hole size column, “M” is the outer diameter in mm).

Standard Tap Markings

Taps have marks on the shank, so you can tell with just a look what type of thread tap you’re working with. The markings include the nominal size, which is the thread size that the tap will take. There’s also the thread form symbol, which identifies the thread family. There’s also tap material, which is usually carbide or HSS. It also typically shows the pitch diameter limit, which tells what tolerance thread will be made. 

Pitch Diameter Limits

Here is a quick guide for threads with a diameter of less than an inch:

• L1 = Basic (B) to B minus .0005
• H1 = B to B plus .0005
• H2 = B plus .0005 to B plus .0010
• H3 = B plus.0010 to B plus .0015
• H4 = B plus .0015 to B plus .0020
• H5 = B plus .0020 to B plus .0025
• H6 = B plus .0025 to B plus .0030

Note: You can find these limits in G-Wizard’s thread database as well.

Choosing Thread Taps

When you’re choosing which thread tap to use, there are four main factors to think about so you can up your chances of success: 

Workpiece material: Various materials have different levels of firmness and there will be a tap suitable for each level. Some will work better than others on different materials, i.e., a machine tap works well on harder materials, but a fluteless tap is best for soft materials. 

Tap material: You’ll have to choose this according to the material of the piece you want to work on, e.g., carbide steel taps can cut threads quickly, and are strong enough to handle hard materials like cast iron.

Hole type: Depending on what hole you need to make, there will be a tap up to the task. Taps with 1–3 thread chamfers can create deeper holes, for instance.

Cutting speed: Some taps, i.e., spiral flute, are designed for high-speed work, while others not so much, so you’ll have to know the speed of cutting before choosing your taps.

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