What Size Drill Bit For a 3/8″ Bolt? [Answered]

Navigating the world of DIY can be a challenge, but when it comes to drilling, I’ve got you covered. This concise guide hones in on a common question – what drill bit size do you need for a ⅜” bolt?

Lean on my decades of DIY experience as I explore not just the ideal bit size, but its variations and other critical factors before you power up that drill. Ready to dig in? Let’s drill down the details.

Bolt Size	Drill bit size
⅜“	5/16”

There are two specific drill bits that that you can look for with a ⅜” bolt. They include the following sizes along with the fractional drill bits and letters:    

Tap	Fractional Drill Bit	Letter Drill Bit
⅜” 16 Tap	5/16”	–
⅜” 24 Tap	21/64”	Q

You can also read more about what drill bit to use for a regular ⅜” tap, a ⅜” NPT tap, a ⅜” wedge anchor, and a ⅜”-16 tap.

So now that you know what kind of drill bits you need to use, you can drill a hole that will be large enough to accommodate a ⅜” bolt.

How to Use a ⅜” Bolt

When you’re using a ⅜” bolt, it’s usually to strengthen something or hold it firmly in place. A good example is attaching table legs securely for added stability. Let me explain a few important basics:

1. Bolt vs Screw: Both are used for fastening, but they differ in their structure and use.
   • Screws have threads designed to hold materials together. The hole size corresponds to the screw shaft’s size.
   • Bolts, larger than screws, have their own threads. The hole size should be slightly larger than the bolt’s outer threads.
2. Drilling Process: Using a 5/16″ bit is optimal for ⅜” bolts.
   • Drill a hole deep enough to accommodate the bolt’s threads fully.
   • Once the hole is ready, install the bolt.
3. Bonus Tip: If available, a drill with a torque wrench functionality can make this process even easier and more precise.

Following these steps ensures a successful and sturdy assembly.

When to Use a ⅜” Bolt

Using a ⅜” bolt is usually the go-to choice when you need to secure or reinforce various materials such as drywall, wood, metal, and concrete. Unlike screws and nails, bolts offer an exceptional amount of holding power, making them invaluable for certain projects.

Depending on the project, the use of a ⅜” bolt varies. For example:

• Securing table legs: When you’re working on furniture such as tables, a ⅜” bolt can provide the substantial reinforcement required for long-lasting durability.
• Countertop installation: If you’re dealing with heavy materials like granite or sandstone for kitchen or bathroom countertops, a ⅜” bolt is an excellent choice to ensure everything stays in place.

To get these bolts in, you’ll need a torque wrench. You can use either a manual torque wrench or a power one, depending on your project and comfort level.

However, be cautious with the amount of power and pressure you apply, particularly with materials like wood that can easily be damaged by excessive force.

Use bolts when you’re constructing a structure designed to support a substantial amount of weight. Structures held together by nails or screws may not withstand the strain, but a tightly secured ⅜” bolt gives you the stability you need.

Always plan ahead on where the bolts will be installed. Strategic placement not only ensures even weight distribution but also contributes to the overall stability and longevity of your structure or project.

Other Considerations for Using a ⅜” Bolt

Planning on using a ⅜” bolt for your next project? Great choice – they’re known for their strength and durability. Here’s what you need to know to make the most of them:

1. Choosing Your Tools: A standard corded drill will usually suffice for drilling holes. But, if you have a power tool that doubles as a drill and torque wrench, even better. Make sure you consider if bolts are the best choice for your project or if screws and nails might be more suitable.
2. Additional Fastening: For ⅜” bolts, you may want to use additional pieces such as nuts and washers for extra support. A flat washer that measures 1.000 (USS) or 0.406 (ASE) will fit nicely with a ⅜” bolt.
3. Weight Capacity: A ⅜” bolt can support quite a load. For instance, if you’re installing kitchen countertops, it can handle up to 7,000 pounds with granite (6000 psi) or 4,000 pounds with sandstone (2000 psi).
4. Drilling and Placement: Before you place your bolt, ensure you’ve drilled a hole using the correct drill bit. Mark your areas of placement, and consider using washers for extra reinforcement.
5. Cleaning Up: After drilling your holes, be sure to clean out any dust or debris. This will ensure a smoother fastening process when securing the bolt.
6. Consider Torque: Lastly, consider if you need a torque wrench for your project, especially if you’re working with materials that could get damaged by excess force.

Remember, careful preparation and the right tools can make all the difference in the success of your project.

Final Thoughts

Finding the right drill bit is key. Especially when you need to drill a large enough hole that supports a ⅜” bolt. Drilling holes for bolts is a bit different compared to holes for nails and screws. You’ll notice that a larger drill bit will be needed for bolts because of its larger head size.  

Once you find the drill bit you need, you can get right to work. Drill as many holes as you can and secure them with as many ⅜” bolts as you got.