What Size Pilot Hole for 3/8 Lag Screw


by Brittney Nelson


No Comments

To ensure that your 3/8 lag screw is the correct size for your pilot hole, you will need to measure the diameter of the shaft of the screw. The best way to do this is with a caliper, but a ruler or tape measure can also work. Once you have the measurement, you will need to find a drill bit that is slightly smaller in diameter than the screw shaft.

This will create a snug fit and ensure that the screw doesn’t slip when being driven into place.

If you’re looking to install a 3/8″ lag screw, you’ll need to drill a pilot hole first. But what size pilot hole should you drill? The answer depends on the type of wood you’re using.

For softwoods like cedar or pine, a 1/16″ pilot hole is typically sufficient. For harder woods like oak or maple, you may need to go up to a 1/8″ pilot hole. In general, it’s always better to err on the side of drilling a slightly larger pilot hole than necessary. That way, you can avoid stripping out the wood and ruining your project.

Pilot Holes Sizes

Pilot Hole for 3/8 Lag Bolt in Wood

If you’re looking to mount something heavy in wood, you’ll need to use a lag bolt. These specialized screws are designed for added holding power, making them ideal for projects that require extra strength. But before you can drive your lag bolt into the wood, you’ll need to drill a pilot hole.

Here’s what you need to know about drilling a pilot hole for a 3/8 lag bolt in wood. The first step is to select the right drill bit. For a 3/8 lag bolt, you’ll need to use a 7/16 inch drill bit.

This will ensure that your pilot hole is just the right size for the screw, allowing it to bite into the wood and create a strong hold. Next, mark out where you want to place your pilot hole using a pencil or marker. Then, take your drill and carefully align the tip of the bit with your marked spot.

Apply gentle pressure as you start drilling into the wood. Once the bit has pierced through the surface of the wood, continue drilling until it reaches its full depth. Finally, remove the drill bit from the pilot hole and insert your 3/8 lag bolt into place.

Use a wrench or socket driver to tighten it down, and voila – your heavy item is now securely mounted!


Also Read: How to Measure Screw Size

What Size Predrill for 3/8 Lag Bolt?

When it comes to predrilling for 3/8 lag bolts, the size of the drill bit you’ll need will depend on a few factors. First, consider the diameter of the shank of the lag bolt. The thicker the shank, the larger the drill bit you’ll need.

Second, take into account the length of the lag bolt. The longer the bolt, the deeper you’ll need to drill. Finally, factor in whether or not you’re using washers with your lag bolts – if so, you’ll need to make your pilot holes slightly larger in order to accommodate them.

In general, though, most 3/8″ lag bolts will require a 7/16″ drill bit for their pilot holes. With this size bit, you should be able to easily accommodate all but the longest and thickest-shanked bolts without any issue. If you’re unsure about what size drill bit to use for your particular application, err on the side of going up one size – it’s always better to have a hole that’s too big than one that’s too small and results in stripping out yourlag bolt threading.

What Size Head is on a 3/8 Lag Bolt?

When it comes to finding the right lag bolt for your needs, one of the most important factors to consider is the size of the bolt head. The head of a lag bolt is measured in two ways: diameter and height. The diameter is the width of the head, while the height is how tall the head is.

For a 3/8″ lag bolt, you’ll need a head with a diameter of at least 9/16″ and a height of at least 1/2″.

What Size Hole Do You Drill for a 3/8 Screw?

A 3/8″ diameter screw will require a pilot hole that is slightly smaller in diameter. The best way to ensure an accurate size pilot hole is to use a drill bit that corresponds to the numbered size of the screw (3/8″). For example, if you’re using a #8 screw, then you would want to use a #7 drill bit. If you’re using a #10 screw, then you would want to use a #9 drill bit.

It’s important not to make the pilot hole too large, as this will make it difficult for the screw to grip and could cause stripping. It’s also important not to make the pilot hole too small, as this could cause the head of the screw to break off.

Do Lag Screws Need Pilot Holes?

Lag screws are one of the most versatile and strong types of screws. They are commonly used in woodworking and construction, and can be used to join two pieces of wood together or to secure a piece of wood to a different object. Lag screws are also known as lag bolts.

Most lag screws have a hexagonal head, which allows them to be driven in with a wrench or socket. The threads on lag screws are Tapered, meaning that they get wider towards the tip of the screw. This tapered design helps the screw grip into the material it is being driven into.

Lag screws do not typically need pilot holes, but there are some instances where drilling a small hole first can be helpful. If you are driving a lag screw into hardwood or another type of material that is difficult to penetrate, drilling a pilot hole can make it easier to insert the screw. Pilot holes also help prevent the head of the screw from splitting the wood as it is being driven in.

In general, it is always best practice to drill a pilot hole before inserting any type of screw, regardless of whether or not it strictly needs one.


You’re in the middle of a project, about to drive a 3/8″ lag screw into some lumber, and you pause. What size pilot hole should you drill? If you drill too small of a hole, the shank of the lag screw will bind in the hole and it’ll be difficult to drive.

But if you drill too large of a hole, the threads won’t grip as well and the head may pull through the wood. So what’s the answer? The general rule of thumb is that the pilot hole should be 1/16″ smaller than the diameter of the shank (the part of the screw that isn’t threaded). So for a 3/8″ lag screw, you would drill a 7/32″ pilot hole.

But there are always exceptions to rules like this – so read on to learn more!

Leave a Comment