What Size Drill Bit for 10mm Tap?

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10mm taps are generally used to through holes and start blind holes. If you’re going to use one, you should know what size drill bit for a 10mm tap to get the proper application. In this article, we’ll tell you everything you need to know about the size of drill bits for a 10mm tap.

What Size Drill Bit for a 10mm Tap?

For a 10mm tap, there are 3 variations to consider when checking for the size drill bit. Below are 3 types of standard 10mm tap and their corresponding size drill bit.

  • 10mm x 1.5 – 8.7mm
  • 10mm x 1.25 – 8.9mm
  • 10mm x 1.0 – 9.1mm

For tapping drills, one size doesn’t fit all, unlike the #10 screws size drill bit of 7/64″ for softwood. You have to consider the threaded percentage for the particular tapping application. In most applications, a lower percentage of thread means a lesser chance for your tap to break in the hole, meaning longer usage life.

Following the right size drill bit, you should encounter no problems drilling 10mm taps. Drill bit size scales with tap size, so expect a ⅛ tap to have a smaller drill bit size.

Tips for Using Small Drill Bits

Stop Every Now and Then

As I mentioned before, drilling causes friction which in turn creates heat. The heat can dull the drill bit, which you must sharpen more often. The heat may also cause deformities in your workpiece, which you want to avoid.

Rest your drill after drilling 2 to 5 light applications to avoid this. Most people would just let their drill bits rest for a minute or two before resuming to drill again.

Another way is to dip the drill into cold water 5 to 20 seconds after drilling to stop it from heating up. This resets the heat threshold allowing you to drill again without worry of overheating.

Lubricate Drill Bits to Make Them Last Longer

Lubrication decreases the friction between surfaces. This means less heat is generated, making your drill bits less compromised when they’re not that heat resistant. It also keeps your drill bits working longer since it coats drill bits with protection against rust and other stuff.

Some surfaces like aluminum, brass, or cast iron don’t necessarily need lubrication to drill properly. It doesn’t always have to be the case as lubrication also offers other things.

Lubrication boosts your drilling speed since there is less friction. If you’ve drilled with and without lubrication, you probably noticed that drilling without lube is slower, especially if you’re not forcing your way through.

Never Force the Drill Bit

It’s not a good decision to force the drill bit through the material most of the time. The speed of the drill bit won’t change even if you force it through, and it will only do more harm than good.

You also might end up breaking the bit if you’re being forceful. Small drill bits are usually brittle so you need to use them carefully. Forcing it through also blunts the bit’s tip, making it unusable.

In the end, you want to ensure that the drill bit you’re using is compatible with the surface. If it is and still doesn’t drill effectively, other underlying problems might need to be addressed.


10mm taps have various options, so the drill bit sizing also differs depending on the length of the tap. Make sure you check what 10mm tap you have before deciding on the drill bit size. A lower percentage drill is great for hard or tough materials, so adjust your tap accordingly.