What Size Drill Bit for a 5/8″ Tap?

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⅝” taps are commonly used for cutting oil when cutting threads in metal. If you want to know what size drill bit for a ⅝” tap is, continue reading. This article will help you with the proper sizing and know more about the ⅝” tap. 

What Size Drill Bit for a 5/8″ Tap?

A ⅝” tap requires a size drill bit of 17/32”. However, the two sizes are ⅝”, so it’s better to be clear about this. The two are different and have different drill bit sizes, so you must know what ⅝” tap you’re working with.

The first one is the ⅝ – 11 NC. Use a 17/32” drill bit or .5312 inches (in decimals). For ⅝ – 18 NF, the drill bit size would be 37/64” or .5781 inch in decimals. There’s a clear difference in size, just like the variations for 10mm taps.

The ⅝ – 11 NC is like the 1-64 tap with drill bit size #53 as it belongs to the NC or national course, whereas the ⅝ – 18 NF belongs to the national fine. Coarse threads have larger pitches compared to fine threads. This means it has fewer threads per inch or a bigger distance between threads.

Tips for Using Large Drill Bits

Monitor Your Progress When Drilling

As you are drilling, check your work to see if there are any adjustments you need to do. If there are lugs or jams, remove it and clean them up. You can use the bit to clear the hole from debris.

Make it a habit to pull out the drill bit every now and then and blow it off. This is important when you are drilling wood. Any flakes or chips of wood can get stuck in the bit.

The flakes and chips can make your drill bit heat up faster. This may be unnoticed by you. When your drill bit gets hot, it will function effectively less.

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.

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.

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.


⅝” taps can vary in their threading. Make sure you know what thread you are using. It can either be a coarse thread or fine thread, and they differ in drill bit size. It also changes depending on the diameter.