What Size Drill Bit Do I Use To Drill A Hole For A Carriage Bolt?

carriage bolt drill size

A common question we get when discussing carriage bolts is “What size drill bit do I use to drill a hole for a carriage bolt?” The answer is simple. Use the same size drill bit as the diameter of the bolt. If you are using a 1/2″ diameter bolt use a 1/2″ drill bit.

Installing A Carriage Bolt

Carriage bolts are very misunderstood and yet very simple to install. Made primarily for wood, carriage bolts have a square shoulder right below the head. This shoulder is designed to catch on wood and be pulled into it (by tightening the nut). Often you will find the domed head of a carriage bolt countersunk into the wood. To learn how to make a countersunk hole carriage bolt in wood you can check out this video we made: How To Drill A Countersunk Pilot Hole.

SHOP CARRIAGE BOLTS

Step One

The first thing to do when installing a carriage bolt is to determine the diameter of your carriage bolt. After you figure out the diameter with a thread gauge or other measuring tool, find a wood drill bit with the same diameter and then get your drill ready.

SHOP THREAD GAUGES SHOP WOOD DRILL BITS

Step Two

Now that you have your drill bit, mark the wood and drill out the hole. Depending on the type of wood drill bit you use to make the hole, the carriage bolt may slide right into the hole or be very tight. If it is very tight grab a hammer and tap the rounded head of the bolt so it slides into the hole. *Pro Tip: Since you already have the hammer out, once the hammering in a carriage bolt square shoulder gets down to the wood give it a couple solid hits, so the square portion begins to sink into the wood.

SHOP HAMMERS

Step Three

Take a washer and nut and fasten them to the carriage bolt against the wood. As you tighten the nut against the washer, it will pull the square shoulder into the wood preventing it from spinning. Once the domed head of the carriage bolt is tight against the wood the carriage bolt is installed.

SHOP WASHERS SHOP NUTS

Conclusion

Carriage bolts are surprisingly simple to understand and yet many people still struggle with them. Hopefully this post will help you to understand which size tightening a carriage bolt drill bit you will need and how to install a carriage bolt into wood.

What is Torque Control?

Torque Control and Related Terms

Torque is the force applied to something to make it spin (rotate) in machinery. Torque in relation to fasteners is the resistance faced when installing a fastener. Torque control then is simply controlling the amount of torque placed on a fastener without damaging it by over-tightening.

Prevailing Torque	Measure of a screw or nuts frictional resistance to rotation.
Prevailing “Off” Torque	Highest back-off torque on a torque wrench on the first rotation of a screw or nut upon removal.
Installation Torque	The initial torque amount used to install a fastener before Pre-load.
Breakaway Torque	The minimum torque required to start rotation into a nut (in the case of a bolt) or into a pre-tapped hole (in case of a screw).
Breakloose Torque	Minimal torque required to begin the disassembly of a fastener assembly.
Seating Torque	The torque required to produce pressure onto the installation material causing compression by the fastener.

Torque Wrenches are one of the easiest ways to ensure proper torque is met. Simply set the wrench’s torque and then when the maximum is reached the clutch will slip. This slip means the wrench stops putting any more torque on the fastener and it has reached its optimal torque.

How to Install and Remove a Carriage Bolt

Carriage Bolt Install and Removal

The Setup

The first thing we need to do when installing a carriage bolt is to make sure we have the right parts and tools to do so. For this job we will need a:

Hammer
Drill
Drill Bit
Piece of wood
Carriage Bolt
Nut
Washer

For our example, we have already pre-drilled the hole into a piece of 2×4 and attached it to a vice. This will act as our installation surface for our carriage bolt.

Understanding A Carriage Bolt

A carriage bolt is a bolt with threading all the way up the shank to a small square shoulder, with a domed head. The square shoulder of a carriage bolt stops it from spinning as it is screwed into the surface of a material. You would not typically use this type of bolt on very hard wood as it may not properly dig into the material, which would cause the bolt to spin in place. Once you seat the bolt through the hole, it is the job of the nut and washer to pull the bolt into the material tightly. Since there is no drive device for the domed head of the bolt, this is the only way to install it.

The Install

The installation process is fairly simple. First, you drill a hole into the wood for the appropriate size (diameter) of the bolt. Next you slide the bolt into the hole (you may need a hammer as the hole should be just big enough for the bolt to go through).

Now that you have the nut through the wood it is time to attach the nut and the washer. Place the washer on the rear side of the bolt followed by the nut. The washer will help to distribute the force you are about to put onto the nut to pull the bolt into the wood. This will not only protect the wood on the back side but also keep the bolt from digging into it and getting stuck.

As you tighten the nut, the square shoulder on the bolt will be pulled into the wood. Once the underside of the head rests against the wood, the carriage bolt is officially installed.

The Removal

Removing the carriage bolt is a fairly simple process. First, you will want to twist the nut close to the end of the bolt. DO NOT TAKE THE NUT ALL THE WAY OFF THE BOLT, you will need it to help move the bolt along.

Once the nut is backed off to the end of the bolt, hit the nut with a hammer. The force should start moving the square shoulder out of the wood. As you move the bolt further out the nut will get closer to the wood. When this happens continue to back out the nut and strike it again. Repeat this process until the bolt is loose enough to take out by hand or the nut can no longer grip the bolt.

If you find the bolt is stuck but the nut can no longer attach to the bolt, use the nail remover attached to the hammer and use it to pry the bolt out of the hole.

It’s That Simple

There you go now you know everything you’ll need to know about installing and removing carriage bolts. As always, Albany County Fasteners stresses the need for protective gear while working with dangerous materials. Remember to ALWAYS wear safety glasses while drilling to protect your eyes and wear protective gloves that fit to keep your hands safe from harm as well.

Full Installation and Removal process you can find on our Youtube channel

Why Do Some Bolts Have Shoulders?

There are many different types of bolts available for use. From carriage bolts to hex cap screws, many of them can be seen sporting a shoulder (area near the head of the bolt without threading). But why? What does this area do?

Shoulder or Shank?

A shoulder or shank is a term that can be used to describe this unthreaded portion of a bolt. For different types of fasteners the appearance of a shank can mean different things. We made a post a while back about why would screws have a shank; Bolts have a shank for an entirely different reason though.

Bolt Shoulders

Bolt Shoulders exist for two reasons. The first is to create an area on the bolt where sheering is less likely to occur. If a load is pulling sideways against the unthreaded area of a bolt then the bolt will be less likely to snap as the areawhere the pressure is being placed is stronger than the threaded portion. The second reason for a shank is to allow for more versatile uses. This shank can act as an area for something attached to the bolt to be moved around.

Installing Wedge Anchors

Installing Wedge Anchors in Concrete

Wedge anchors are fasteners designed for use in masonry materials (most commonly concrete) and used to secure materials and equipment. Concrete wedge anchors are designed to go into a pre-drilled hole and expand, creating a grip so they cannot be “pulled out” or removed. Today we will be reviewing the proper installation of a post base into a concrete floor.

What will you need?

Before we begin let’s make sure we have the proper tools for the job.

Step One

The first thing you need to do when installing a wedge anchor is choose the proper anchor material. Wedge anchors come in many materials and all serve different purposes. Stainless steel and hot dip galvanized are two very popular wedge anchor materials, but the correct material varies by application. Not sure what material you need? Check out our Material Guide to learn about all the different materials available.

wedge anchors

Step Two

Once you’ve chosen a material, its time to get your drill ready. When installing a wedge anchor, it’s important to have a minimum of 2-1/2 inches embedded into the concrete. There should also be at least an inch exposed, enough for the attaching material to grab onto. To measure ours, we placed the wedge anchor about an inch below the tip of the SDS drill bit and then used blue painters tape to mark off the drill where we should stop drilling. Marking the stop point with blue tape will allow you to drill consistent holes and prevent you from over/under drilling.

Step Three

drilling into concrete

Now that we’ve applied our drill bit with tape, its time to begin the drilling. BUT NOT SO FAST. First we need to put on our safety goggles and gloves, always wear safety gear when cutting. Now that you are safe and ready to work, simply apply pressure to the place you want to drill and let the bit begin to do its work. Once your drill bit reaches the blue painters tape, you will know that the hole has reached the necessary depth and you can stop drilling.

Step Four

hammering in wedge anchors Carefully brush away any of the debris from drilling to clear the hole and begin installation of the anchor. The next step is to insert the masonry anchor into the hole. It should be a very tight fit and will need to be hammered into place. The end result should leave about an inch (or more depending on how much room you need) above the surface to allow for anchoring.

wedge anchor ready for post base

Now that the anchor is installed we can apply the post base, square washer, and nut to the wedge anchor. After placing them on, you screw the nut onto the wedge anchor creating a strong, sturdy anchoring station. Now that you’ve completed the installation, take a step back and admire your handiwork. This post base is now ready for the next step in your building project.

ratcheting on postbase Anchored postbase

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Category: Bolts

What Size Drill Bit Do I Use To Drill A Hole For A Carriage Bolt?

What Size Drill Bit Do I Use To Drill A Hole For A Carriage Bolt?

Installing A Carriage Bolt

Step One

Step Two

Step Three

Conclusion

Looking For More Blogs Like This One?

What is Torque Control?

Torque Control and Related Terms

Looking For More Blogs Like This One?

How to Install and Remove a Carriage Bolt

Carriage Bolt Install and Removal

The Setup

Understanding A Carriage Bolt

The Install

The Removal

It’s That Simple

Why Do Some Bolts Have Shoulders?

Why Do Some Bolts Have Shoulders?

Shoulder or Shank?

Bolt Shoulders

Looking For More Blogs Like This One?

Installing Wedge Anchors

Installing Wedge Anchors in Concrete

What will you need?

Step One

Step Two

Step Three

Step Four

Looking For More Blogs Like This One?