Planning a DIY project involving a ⅝” tap? I’ll guide you on choosing the correct drill bit, provide usage instructions, and highlight important factors based on my years of practical experience. Let’s get started.
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What Size Drill Bit For ⅝” Tap?
For a ⅝”-11 tap, a 17/32″ drill bit is required, whereas a ⅝”-18 tap necessitates a 37/64″ drill bit. When tapping a ⅝” hole in metal objects like bolts, nuts, and screws, a drill bit size of 11/32 inches or 8.73 millimeters is recommended.
Tap size | Drill bit size |
⅝” | 37/64” |
There are two different tap sizes and pitches that are within the ⅝” range. Each of them have their own corresponding drill size that you will need to use. Knowing the type of tap you are using will make a difference between using one drill bit size and another.

The smallest of details can also make the difference between the perfect project from start to finish to a disaster.
Tap Size (and Type) | Drill bit size |
⅝”-11 Tap | 17/32” |
⅝”-18 Tap | 37/64” |
Please note that the major difference between the two is the thread pitch. The 11 and 18 taps have different threads per inch. It can also influence how long the tap is. The 11 tap will have lesser threads in comparison to the 18 tap.
If you are planning on installing a shorter tap, you’ll want to go with the ⅝”-11. This means you will be using the 17/32” drill bit for the pilot hole. Since you are working with metal, you’ll want to make sure that you get it right.
How to Use a ⅝” Tap
If you want better results and stability, I really recommend that you use a drill press. You’ll also want to make sure that the metal piece is secured to a drill press vise. This will ensure that your holes will be perfect so the tap can fit straight through.
Here are the steps to follow:
- Choose the correct ⅝” tap for your project, considering the length of the tap required.
- Set up your equipment: Secure the metal piece to a vise, ensuring stability for accurate drilling.
- Select the right drill: For precision and power, consider a drill press designed for metal or a corded drill. Both are equipped to handle thicker metals effectively.
- Get a tap and drill set: Tap and die sets are readily available at local hardware stores or online. For specialized tasks, a tap and die set might be beneficial.
- Prepare for drilling: Use a center punch to create divots in the metal where the holes are to be drilled. This guides the drill bit and prevents it from wandering.
Remember, any movement during drilling can lead to uneven holes that can cause issues when tapping. Ensure your setup is secure for a smooth, successful project.
When to Use a ⅝” Tap
The best time to use a ⅝” tap is when you are working with metal materials. You can use a tap to cut through metal and create threads for screws and bolts.
Without taps, you won’t be able to create the holes you’ll need for screws and bolts to fuse metal materials together.
- Know when to use a ⅝” tap: This tool is essential when working with metal materials. It cuts threads for screws and bolts, enabling fusion of metal pieces.
- Prepare the tap: After drilling the hole in the metal, attach a ⅝” tap to a T-handle. This provides firm control while creating threads.
- Lubricate: Apply lubricant to the drilled hole before tapping. This makes the process smoother and prevents wear on the tap.
- Maintain cleanliness: Clear away debris and metal shavings after drilling. A clean hole simplifies the tapping process, reducing the chance of grit hindering your work.

Other Considerations for a ⅝” Tap
Before starting your project, determine whether or not you have the right tools you’ll need. This includes a corded drill (or a drill press), a vise or C-Clamp, drilling oil, a T-handle, and other pertinent tools.
- Tools: Ensure you have the necessary tools, including a corded drill or drill press, vise or C-clamp, drilling oil, a T-handle, and other relevant tools.
- Consider the Metal: The choice of drill can depend on the metal. For softer metals like copper sheets or aluminum siding, a lightweight cordless drill may suffice. For harder metals such as steel or cast iron, more consideration is needed.
- Choose the Right Drill Bit: Use high-quality drill bits made from durable materials like cobalt or titanium. Standard drill bits won’t cut through steel. For aluminum, due to its low melting point, cobalt drill bits are the best choice, as they dissipate heat quickly and prevent excessive heat build-up during continuous drilling.
Final Thoughts
While the size of the drill bit always matters, so does the material that will be able to cut through the metal. But whatever drill bit you choose, make sure it’s strong enough to pierce through steel. After that, use your ⅝” tap to thread the holes for screws or bolts and be proud of the job you’ve done.