What Size Drill Bit for a #12-24 Tap? [Answered]

Although tapping into metal is not always the most common home improvement project, it does happen sometimes. If you are making holes before the tapping procedure, you need to make the hole is smaller than the tap but large enough that the tap will cut the edges of the base material properly.

If you are looking to start tapping and threading into metal, you probably want to know what size drill bit you need for a #12/24” tap.  

What Size Drill Bit for #12-24 Tap?

For a #12-24 tap, you will need a #16 drill which is equivalent to 11/64”.

The recommended tap drill to use for all these listed above in the chart will require you to use a 75% depth of thread, unless you know you need to use another percentage.

If you are new to using a drill, you are probably safe using the 75% percentage as changing the percentage is usually something done by professionals or those who have more experience with drilling the different materials.  

Since you are probably drilling into metal though, you might need to change the percentage depending on the metal you are drilling. Only very hard materials need to be drilled with a different percentage- usually 50%.  

This change in percentage to something lower is only needed for very hard materials including steel and iron. If you aren’t sure what percentage you need, check the manufacturer’s instructions or ask a worker at the local hardware store.  

You might also be interested in my guides on drilling a #10-24 Tap or a #12 Tap.

How to Use a #12-24 Tap

Here are the steps to using a #12-24 tap:

1. After you have drilled the initial hole and you have the bolt and screw ready for comparison, you can de-burr the edge of the hole. This can remove any sharp edges that might affect the bolt. If you are a chamfer, you might also want to add it at this stage. It will make tapping easier.  
2. You also need to make sure you clean out all chips, dust, and other debris. This will often accumulate inside the hole when you are drilling and not cleaning it can affect the ease at which the bolt can go into the hole.  
3. Next, it’s time to set up the tap. You will need to use a 90-degree tap guide if you have one as it makes the process much easier. If you don’t use a guide, you might put too much pressure on the hole and the tool you are using. This can make the tap lean to the side and you will end up with a crooked tap. By using the guide, you can avoid this problem.  

When to Use a #12-24 Tap 

You can use a #12-24 tap when you are planning on pecking threads. This is a type of tapping that is very convenient and easy to use. You will go forward a short distance with the drill and then you will be able to back off a bit. This allows the drill bit to keep from overheating or breaking under torque when you are drilling into the metal.  

When you are drilling with metal, you might find that your drill bit overheats easily because of the friction and metal to metal touching. Pecking can be a good way to make sure you do not experience overheating.  

If you aren’t sure how to peck, you can put the drill into the base material for a full turn and then a half turn out. Some people also go in for a full turn and then remove the tap. You can then clean out the hole completely, do it for two turns and then repeat until the hole is fully tapped.  

This can take a long time and most people don’t remove the tap and clean out the hole every time if they are trying to complete the project faster. If you have the patience and the time for this method though, you can be sure you have very even thread tapping.

Other Considerations for a #12-24 Tap

If you have never drilled for tapping before, you might also be looking for some more details or more advice on what to do. Once you have the drill bit size and the thread percentage you want to use, you can start the drilling process. Since you are drilling into metal, you will need to clamp the material, or it might spin. Spinning is dangerous because it can injure you and make it very hard to drill.  

Any time you are drilling metal, you need to make sure you use at least two clamps. You also need to wear safety goggles and very thick gloves.  

Once you have the material and the safety materials with you, you can mark the area to be drilled. Most people use masking or painter’s tape as it’s easy to see and not very expensive so you can purchase it even if you are on a budget.  

If you are using soft metal or a material that is thin or flexible, you need to make sure you have a solid base material behind it. If you don’t use a backing material, you might deform the metal when you begin to drill which can ruin the material and the project.

Once you have the backing, you can put the drill at 90 degrees to the material you are drilling. This will create a perpendicular angle. If you do not use the right angle, you will have problems with the tapping and screwing in bolts.  

If you have the money to get extra materials, you might want to get a metal drill press or a handheld drill. Cutting fluid can also make sure your drill bit does not get too hot.  

Final Thoughts

Drilling with a #12-24 tap can be easy if you have the right drill bit size and use the right thread percentage for the material you are using. You can always use a scrap of material to test the drill bit to make sure you are on the right track.