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Lock Blog

A resource for consumers, locksmiths, and security professionals

Can You Replace A Door Knob With A Deadbolt?

by Ralph December 8, 2021

Can you replace a door knob with a deadbolt? The short answer is yes. In most cases, you can replace a door knob with a deadbolt. However, there are some exceptions, and changing locks in this way is not always a good idea.

Before you replace a door knob with a deadbolt, you should review:


Can you put a deadbolt on an inside door?

Deadbolts are rarely appropriate for Interior doors because they are a mismatch of security. Exterior entrances use solid core doors versus hollow core doors that are used on interior entrances. If you put a deadbolt on a hollow core door, the door is still extremely weak.

Do you need a door handle on a door?

 If you don’t want the wind blowing open the door, a contact point where the latch/bolt can be retracted, and the door can be pushed or pulled open is necessary. When you replace a door knob with a deadbolt, your key or thumbturn acts as the handle.

Are all door locks the same size?

USA door locks have a standard size, so they can fit a 2 ⅛ inch diameter bore hole. The cross bore from the bore hole to the side of the door where the bolt or latch will extend is either 2 ¾ or 2 ⅜ inches long. Exceptions include mortise locks, which are often used in commercial settings.

Will a deadbolt fit in a hole cut for a door knob?

To replace a door knob with a deadbolt, you rarely need to make any adjustments to the bore or cross bore holes. In most cases, it will be as easy as removing and replacing. Exceptions include switching to the euro cylinder style deadbolt or otherwise deviating from the standard USA lock type.

Does drilling more lock holes in a door weaken the door?

More holes in a door mean more potential weak points. You can improve door security by adding metal sleeves around your lock hardware or by replacing a door knob with a deadbolt rather than making an additional bore hole and cross bore.

Standard Door Lock Sizes

To replace a door knob with a deadbolt, you are relying on the fact that both the new and old devices have the same dimensions. That means fitting both the bore hole and cross bore that exist on the current door.

Bore Hole – The large hole that goes from the interior to the exterior side of the door where the knob and deadbolt are installed. The hole has a standardized 2 ⅛ inch diameter. 

Cross Bore – The smaller hole in the side of the door that lines up with the strike plate. Your bolt or spring-loaded latch extends out of this hole. The hole is 1 inch in diameter but has two standardized back set lengths of either 2 ¾ or 2 ⅜ inches.

The general shape of door knobs and deadbolts is two pieces on the front and back with the bolt work sandwiched in between. Most modern locks will have an adjustable bolt work length so the device can fit either of the two back set lengths for the cross bore.

How to Replace A Door Knob With A Deadbolt

When you replace a door knob with a deadbolt, there are three essential steps in the process. You want to make sure that your replacement deadbolt fits the bore and cross bore style of your door knob. Then you can take the door knob off the door and install your new deadbolt.

It should be possible to do this work yourself, but for the sake of time and assurance that the process will work, consider contacting a locksmith. Depending on the type of structure the lock is on, you will need either a residential locksmith or a commercial locksmith.

1. Matching Lock Styles

Because the United States uses standardized lock sizes when you replace a door knob with a deadbolt, your deadbolt and door knob will likely already match. Both should have the same diameter for the bore hole, and the bolt/latch distance will match the cross bore.

If both locks do not install into a bore hole and cross bore, chances are they do not match. Refer to the section on standard door lock size for more information about this. The most common exceptions to this rule happen during commercial door lock replacement.

Commercial-grade hardware such as electronic locks or mortise locks require different considerations. For these non-matching locks, replacing a door knob with a deadbolt may require a new door or the assistance of a locksmith.

2. Door Knob Disassembly

The basics of how to change a door knob do not change at this point in the process. The first step is to get the door open. There are methods for removing a locked door knob from the outside, but it comes down to finding a way to get the door open or accessing the interior side of the door.

Disassembling a door knob will always broadly follow this process:

  1. Access the interior side of the door. 
  2. Remove the door knob set screws.
  3. Remove door knobs on both sides.
  4. Unfasten set screws for the latch bolt.
  5. Remove the latch bolt.

With the bore and cross bore hole on the door cleared of all hardware, it is easy to replace a door knob with a deadbolt. The only thing left to do is fit your new deadbolt into the freed-up space in the door.

3. Deadbolt Installation

The lock installation process should be in the instructions that come with your new deadbolt, but the process is remarkably similar to the disassembly of the door knob. It just takes some fine-tuning to get everything working after you replace the door knob with the deadbolt.

The deadbolt installation process is essentially:

  1. Install the bolt into the cross bore.
  2. Check that the bolt work aligns in the center of the bore hole.
  3. Fasten the bolt set screws.
  4. Fit both halves of the deadbolt on either side of the door.
  5. Check that the thumbturn or turning key retracts and extends the bolt.
  6. Fasten the set screws for the deadbolt.

If your bolt is too long/short and does not align in the center of the bore hole, do not worry. Most modern deadbolt locks have an adjustable bolt length so the device can fit either of the two back set lengths. Look for the instructions for how to extend or retract the bolt.

Deciding To Replace A Door Knob With A Deadbolt 

In order to decide whether or not to replace a door knob with a deadbolt, you have to consider the pros and cons. Sometimes the answer to a question like, “can you replace a door knob with a deadbolt?” is another question. Should you?

When most people change interior door knobs, they often do not want to install deadbolts. To find the exceptions to this instance and others like it, we need to know when it makes sense to replace a door knob with a deadbolt.

Pros For Door Knob To Deadbolt Replacement

A deadbolt is a security improvement over a door knob. The force a deadbolt can withstand is greater than what a door knob can take. Also, a deadbolt is much harder to manipulate than the spring-loaded latch of a door knob, which can be opened with a credit card.

The lowest effort you can put into physical security is a deadbolt. When you replace a door knob with a deadbolt, it sends a more concrete message about the desired level of access control. A door knob invites you to turn it, a deadbolt asks if you have a key.

Certain necessary lock changes demand you replace a door knob with a deadbolt. These include instances where the wrong lock was installed initially, or a room is subleased and now needs more security for an interior door.

In many cases, you can use the same brand of deadbolt as your replaced door knob. That means the two locks can use the same key, so there is no need for existing keys to be replaced. Be aware that keeping both locks keyed alike will likely require rekeying your new lock.

Key Takeaways:

  • Deadbolts can withstand more force than a door knob.
  • A deadbolt demonstrates a greater desire to protect a space.
  • Exterior doors should have a deadbolt installed.
  • Your new deadbolt can potentially use the same key as the old door knob.

Cons For Door Knob To Deadbolt Replacement

Before you proceed with this type of deadbolt replacement, your two main considerations should be whether or not you need permission and if a deadbolt is appropriate for the door. In some circumstances, a deadbolt on a door may violate a specific safety ordinance.

When you replace a door knob with a deadbolt, you are making a more substantial adjustment than you would be exchanging one knob set for another. In the case of a renter changing locks, this can be a harder sell to your landlord as it changes uniformity and aesthetics.

You also have to consider what you are hoping to get once you replace a door knob with a deadbolt. For example, many people believe that a deadbolt is more resistant to criminal lock picking, but this is not a security feature you gain from a deadbolt.

In the event that you are upgrading your door knob to a high-security deadbolt, you have to be sure that the door is benefiting from the additional security. For example, an interior door with a hollow core will break even if the lock does not fail.

Key Takeaways:

  • Do not install a deadbolt on a door designated as an emergency exit.
  • Renters may not have permission to replace a door knob with a deadbolt.
  • A deadbolt does not necessarily increase drill protection or lock picking resistance.
  • High-security deadbolts can be undermined by the door.

Final Thoughts

When you replace a door knob with a deadbolt, you gain the security of a deadbolt and lose the look and convenience of a door knob. This is almost always possible, but it is not a good idea for many interior doors and renters.

If you need any help with this or any other type of door lock replacement, make sure to check if there is a United Locksmith near you. And if you have any questions or would like to share your experience replacing a doorknob with a deadbolt, let us know about it in the comments section.

Category: Commercial, Residential, Safety & Security

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