What you need to do before you start

Replacing a front door knob takes about 30 minutes and requires only a screwdriver and the new knob. You do not need to remove the door from its hinges or call a locksmith. The old knob unscrews from the inside of the door, and the new one screws back in the same way.

Before you buy a replacement, measure the distance from the center of the knob hole to the edge of the door. This measurement, called the backset, is usually 2 3/8 inches or 2 3/4 inches. Check your old knob or measure with a tape measure from the hole to the door's edge. Buy a new knob with the same backset, or it will not fit properly in the existing hole.

Also check whether your door has a keyed knob (locks from the outside) or a passage knob (no lock). If you want to keep the lock, buy a keyed knob. If you want to remove the lock, buy a passage knob. The installation steps are identical either way.

Key Takeaways

  • Measure the backset (distance from hole center to door edge) before buying a replacement, as knobs come in 2 3/8-inch and 2 3/4-inch sizes.
  • Remove the interior knob by unscrewing the set screw on the shaft, then pull the knob and collar away from the door.
  • Slide the new spindle through the hole and screw the interior knob onto the shaft until it is snug but not forced.
  • Test the lock and door swing before you finish, because tightening the set screw is the last step and cannot be undone easily.

Remove the old interior knob and collar

Look at the interior knob (the one on the inside of your house). You will see a small screw on the shaft where the knob meets the door. This is the set screw. Using a screwdriver that fits the screw head snugly, turn it counterclockwise until it is loose enough to pull out by hand. Do not force it—if it is stuck, explore a small amount of penetrating oil and wait five minutes.

Once the set screw is removed, grasp the interior knob and pull it straight toward you. It will slide off the shaft. Behind it is a metal ring called the collar or rose. This ring is held by one or two screws on the inside of the door. Unscrew these and remove the collar. You now have access to the shaft that runs through the door.

On the outside of the door, the exterior knob will still be in place. Do not remove it yet. It is held in by the shaft you just exposed. Once you install the new interior knob, the exterior knob will come out on its own.

Install the new spindle and interior knob

Take your new knob and look at the shaft—the metal rod that sticks out from the back. This shaft needs to slide through the hole in the door and connect with the exterior knob on the other side. Slide the shaft through the hole from the inside, pushing it all the way through until you feel resistance. The exterior knob should still be loose on the other side.

Now screw the new interior knob onto the shaft. Turn it clockwise by hand until it is snug against the door. Do not over-tighten—you should be able to turn it with moderate hand pressure, not force. If you tighten too much, the knob will bind and the lock will not work smoothly. The collar should sit flat against the door with no gaps.

Check that the exterior knob is now held firmly in place by the shaft. It should not spin or rattle. If it does, the shaft did not seat properly. Remove the interior knob, check that the shaft is fully inserted, and try again.

find the collar and test the lock

Slide the collar back onto the shaft behind the interior knob. Line up the screw holes and insert the screws. Tighten them firmly but do not strip them—stop when you feel solid resistance. The collar should sit flush against the door with no wobble.

Now test the lock before you tighten the set screw. Turn the interior knob to make sure it rotates smoothly. If you have a keyed knob, insert the key in the exterior knob and turn it—the interior knob should not turn when the lock is engaged. Open and close the door several times to confirm the latch retracts and extends properly. If anything feels wrong, loosen the interior knob, adjust the shaft position slightly, and tighten again.

Tighten the set screw and finish

Once you are satisfied that the lock works and the door swings freely, insert the set screw into the hole on the shaft. Turn it clockwise with your screwdriver until it is snug. This screw prevents the knob from spinning on the shaft. Do not over-tighten—you only need enough pressure to keep the knob from rotating independently.

Test the knob one more time. It should turn smoothly, and the latch should retract when you turn it. The lock should engage and disengage without grinding or resistance. If everything works, you are done. The old exterior knob is now permanently attached to the new interior knob through the shaft, and both will operate as a single unit.

Common mistakes that cause problems

The most common error is buying a knob with the wrong backset. If the backset does not match, the knob will either sit too far from the door or too close, and the latch will not align with the strike plate on the frame. Always measure before you buy.

The second mistake is over-tightening the interior knob. This binds the shaft and makes the lock stiff or non-functional. Tighten only until snug, then test. If the knob is too loose after testing, you can always tighten it more, but you cannot easily loosen it without removing the knob again.

The third mistake is installing the collar upside down or at an angle. The collar should sit flat and flush against the door. If it is crooked, the screws will not hold properly and the knob will rattle.

When to call a professional

If the shaft does not slide through the door hole smoothly, or if the hole is damaged or enlarged, the door may need repair before a new knob can be installed. A locksmith or carpenter can assess the damage and advise whether the hole can be patched or if the door needs replacement.

If you have a deadbolt above the knob, you do not need to touch it. The knob replacement is independent of the deadbolt. However, if you want to replace both, the deadbolt comes out separately and uses a different installation method.

Frequently Asked Questions

Can I replace just the exterior knob and leave the interior one alone?

No. The interior and exterior knobs are connected by a single shaft, so they must be replaced together as a unit. You cannot change one without changing the other. If only the exterior knob is damaged, you still need to buy a new pair.

What if the set screw is stuck and will not turn?

explore penetrating oil around the screw and wait 10 to 15 minutes. Try again with a screwdriver that fits very snugly in the screw head—a loose fit will strip the screw. If it still will not budge, a locksmith can remove it without damaging the knob.

Do I need to remove the door from its hinges?

No. The entire replacement happens with the door in place. You only need access to both sides of the door, which you have when it is closed. Removing the door makes the job harder, not easier.

How do I know if my knob is keyed or a passage knob?

A keyed knob has a keyhole on the exterior side. A passage knob has no keyhole and no lock mechanism. Look at the outside of your current knob to see which type you have, then buy the same type as a replacement.

What if the new knob does not fit in the existing hole?

The hole is probably the wrong size for the backset you bought. Measure the backset again and compare it to the knob specifications. If you bought the wrong size, return it and get the correct one. Do not try to force a knob into a hole that does not fit.