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?

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 woodyou can check out this video we made: How To Drill A Countersunk Pilot Hole.



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.




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 boltsquare shoulder gets down to the wood give it a couple solid hits, so the square portion begins to sink into the wood.



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.




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




Looking For More Blogs Like This One?

Sign up to get new blogs sent directly to your inbox!

By submitting this form, you are consenting to receive marketing emails from: RAW PRODUCTS CORP, 100 Newfield Ave., Edison, NJ, 08837, https://www.albanycountyfasteners.com. You can revoke your consent to receive emails at any time by using the SafeUnsubscribe® link, found at the bottom of every email. Emails are serviced by Constant Contact

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:

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

carriage bolt setup

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).

drill the hole

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.

tighten nut with washer

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.

prepare to remove and loose nut

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.

push out bolt with hammer

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.

removing process is complete

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