What Size of Drill Bit Should Be Used for a #8 Screw? (Pilot Hole)

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Admit it, finding out the correct drill bit size for drilling a perfect hole is not an easy task. You may need different drill bit sizes for various applications. 

And since this is not an activity you perform on a daily basis, you might find it challenging to figure out what size of drill bit for a #8 screw. So, through this post, our engineers extend their helping hand to help you out!

Drill Bit Sizes for a #8 Screw

Screw SizeDrill Hole Size for SoftwoodDrill Hole Size for Hardwood
#51/ 16”5/ 64”
#65/ 64”3/ 32”
#73/ 32”3/ 32”
#83/ 32”1/ 8”
#93/ 32”1/ 8”
#107/ 64”1/ 8”

As you can see, for a #8 screw, you will want to use a 3/ 32″ drill bit for drilling softwood and a 3/ 32″ drill bit for drilling hardwood.

different drill bit sizes

The 1/ 8″ straight drill bit is the nearest match you can obtain to the diameter of #8 screws without threads. This figure is equal to 3.175 millimeters or 0.125″. 

In case you need to craft a tapered pilot hole, you can use a tapered bit with a bit larger diameter. Our engineers suggest using 11/ 64″, 4.36 millimeters, or 0.071″ bit.  

How to Find Out the Size Of Drill Bit for #8 Screws?

You will need to identify the size of the drill bit for the #8 screws to create pilot holes that will allow these materials to be securely attached. 

The drill bit’s size used to create pilot holes for various types of fasteners indicates the hole’s diameter. However, this shouldn’t mean that the hole’s diameter is the same as the diameter of the screws.

drill bit for #8 screw
Most tool kits come with a wide range of standard sizes for different types of drill bits. If you’re following the ISO standard, you’ll typically refer to bits in millimeters, while the American National Standards Institute uses fractions of inches. Most commercial drill bits have a narrower diameter than the advertised number indicated due to the way the trajectory of the drill bit changes.  In most cases, a center punch and drill tolerance of .080 inches or 2 millimeters is required for manual applications. This tolerance drops to .020 or .5mm for more precise work.

How Drill Bit Sizing Works for a #8 Screw

One of the most critical rules for choosing a suitable bit for a specific type of fastener is to ensure that the diameter of the bit matches the shaft of the tool. This ensures that the protruding threads are not detracted from the overall appearance of the part.

Although this rule may be helpful in certain conditions, it should not be applied in every situation. Take into account the various aspects that affect how materials behave and how they hold weight. 

choosing the right drill bit for a screw

Also, it’s important to take into account the various types of bits when making pilot holes. For instance, using a straight drill bit can craft U-shaped holes along with straight walls.

Depending on your application, you can use a V-shaped pilot hole or a tapered pilot hole. A more reliable connection is often made with a larger drill bit diameter, while a more compact connection is often made with a smaller one.

What Do #8 Screws Mean?

There are 16 standard sizes in the sizing system of screws. The numbers range from 000 to 14. The #8 screw, in particular, has a diameter of 0.164″ – with 5/ 32″ as the nearest fraction. In fact, a #8 screw can have 32, 36, or 40 threads per inch. 

These are commonly used screws for a wide range of applications. So, when working on various projects, it’s essential to know the size of the drill bit for the #8 screw. Having the proper #8 screws is very important for wood construction projects. These tools can be used to connect wood to a wall, secure thick board, attach fiberboard, and attach door frames. It can also prevent any stripped wood screw hole in your wood project. 

screw sizes

Additionally, it is commonly used for attaching sheet metal components. You’ll typically find these screws with threads and pan heads covering the whole length of the bolt.

Do Different #8 Screws Require Different Types of Drill Bits?

Yes, #8 require different drill bit types. So, before you start working on your #8 screws, inspect the tip of the screws. If you’re going to use a flat point machine screw, then we suggest using straight bits.

If you’re using #8 screws with a self-drilling tip, you may opt for a tapered or straight bit. But, using a tapered one can transpire in a more robust and more precise connection.

The following are the best drill sizes for: 

Straight Bit

You can use 1/ 8″ or 3.17 millimeters for hardwood and 7/ 64″ or 2.77 millimeters for softwood.

attaching drill bit

Tapered Bit

We recommend using 11/ 64″ or 4.36 millimeters of hardwood and 5/ 32″ or 3.96 millimeters for softwood.

Sheet Metal Fasteners

If you’re working with pierced holes, you’ll need a pilot hole of 0.137 inches. If you’re using clean punched or drilled holes, you’ll need a pilot hole of 0.113 inches.


You’ll need to use wall anchors for your drywall. The size of your drill bit should coincide with the diameter of the wall anchor you’re using. You can also go over the diameter by 1/16.

What is the Right Size to Use for a #8 Screw?

A 1/8″ straight jobber drill bit is ideal for working with various types of hardwoods such as maple, oak, and walnut [1]. It’s also a good choice for pilot holes in the lower part of a #8 drill. But how do you screw into wood without using a drill? Is it possible? Find out next. 


What size of drill bit do I use for a #8 screw in metal?

The recommended drill bit size to use for a #8 screw in metal is 1/ 16″ to 3/16″ for small twist bits. But, for larger twist bits, we suggest using 11/ 16″ to 1″ drill bit. 



Knowing what size of drill bit to use for a #8 screw is vital to getting the best drilling results. So just before starting on a project, make sure you have prepared the correct drill bit for your #8 screw or whichever screw size you’re using. 

Overall, we suggest using a 1/ 18″ drill bit for most attachments. But, it would be best if you did not forget to take notes of the properties of the materials you’re using on the project. 

Robert Johnson is a woodworker who takes joy in sharing his passion for creating to the rest of the world. His brainchild, Sawinery, allowed him to do so as well as connect with other craftsmen. He has since built an enviable workshop for himself and an equally impressive online accomplishment: an extensive resource site serving old timers and novices alike.
Robert Johnson
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