What Size Drill Bit for a 1” NPT Tap?

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The 1” NPT tap is a common tap mainly used for threading ferrous and non-ferrous materials. 1” NPT taps are generally made of steel and are usually heavier than most taps If you want to know what size drill bit for a 1” NPT tap is, read further.

What Size Drill Bit for a 1” NPT Tap?

A 1” NPT Tap needs a size drill bit of 1 5/32 inches or 1.1563 inches in decimals. NPT taps are also called pipe taps and don’t confuse them with NPTF taps and tapered taps like the 4-40 tap.

Person screwing door hinge with a drill

NPT taps can be carbon steel, HSS, or Interrupted thread NPT taps. Carbon steel NPT taps are generally used for cleaning or re-threading damaged or jammed pipe threads like the 3/4” NPT tap with a size drill bit of 59/64″. High-speed NPT pipes are for making new threads and for re-threading also.

If you plan to use NPT threads, do know they require a sealer like Teflon tape or pipe compound.

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.

Keep A Spare Set of Drill Bits

You never know when your drill bit dulls or breaks. 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.

Person fastening screws into a wooden panel with a drill

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.

Avoid Jamming Your Drill

One common thing when using large drill bits is jamming. It’s a common mistake amateur drillers make since they usually apply more pressure when drilling, which leads to jamming. You should learn how to avoid jamming your drill.

When you jam your drill, you might have to replace the tip, and your drill’s lifespan will shorten. You want to avoid spending more than you should when it’s avoidable. One thing you can do is not apply too much pressure when drilling.

Also, feel the drill and spot when you think it is slowing down. Pull it out when you think it’s slowing down and let it cool for a while, cleaning off any debris stuck in the drill.


1” NPT taps need a large drill bit size of 1 5/32 inches and can be used for iron, plastic, and steel materials. They’re mostly used for threading various materials. If you’re gonna use them, make sure to have a sealer for the threads.