What Size Drill Bit for an 8-32 Tap?

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8-32 taps are common taps used for threading metals for screws and bolts. Before doing so, you must identify what size drill bit an 8-32 tap should be. You should know that the sizing of this one is only in inch-decimals and not in fractions.

What Size Drill Bit for an 8-32 Tap?

An 8-32 tap needs a size drill bit of 0.1360 inches in decimals or a drill bit size of #29. It is roughly the same as the 3.454-millimeter drill bit and is classified as a National Coarse thread or UNC (Unified National Coarse), just like the 5-40 tap.

Close up of a drill bit

The #29 drill bit size can also be used by the #8-36 NF tap, which is an entirely different tap. The 8-32 tap doesn’t have a fractional tap size. The 8-32 tap is a general-purpose tap like the 2-56 taps. It is used for steel, aluminum, zinc, and other ductile materials.

Tips for Using Large Drill Bits

Learn the Proper Safety Precautions

When handling large drill bits, it’s important to practice safety to avoid accidents. You don’t know what might happen when drilling, or you might have overlooked something.

That’s why it’s not bad to learn about safety practices when drilling. Practice them and make it a habit when working on a drilling project.

One thing you can start with is wearing protective gear such as:

  • Drilling hand gloves
  • Masks
  • Safety glasses or goggles
  • Tight clothing

Starting with these and making it a habit to wear one will minimize the chance of accidents. Reading the manual before you start using the drill is also a great habit.

Man holding a cordless drill while working on a DIY project

Keep A Spare Set of Drill Bits

You never know when your drill bit dulls or will last. So having spare sets help replace them immediately. Another benefit of using two sets of drill bits is you can alternate them, so you have a sharp one at the ready.

Some professional drillers even use them at the same time. They use the new set of drills to drill a hole. The premise is that it keeps the sharper set for longer. After starting the hole, they switch to the old and sharpened set to finish the drilling making it less prone to dulling.

Make Use of the Hammer Action

Some drills have the hammer action feature. This allows you to “punch” on a hard surface repeatedly. For example, if you’re drilling through concrete, you might want to turn on the hammer action to make the drilling efficient. 

Hammer action is a great feature, especially when using large drill bits for concrete. Concrete is hard to drill without the right equipment.

The hammer action makes a vibration that transfers to the drill bit that, gives it better penetration. This will lessen the time for you to drill on concrete and be less taxing on the drill bit since it’s supported by the hammering motion to penetrate the surface.


8-32 are hand taps built for general purposes and can be used in most materials. Make sure you use the correct sizing and apply it properly in decimals since fractions aren’t an option.