To get in and out of most rooms in your home, you'll need to use a door handle. No matter how it looks on the outside, most of them work the same on the inside. Let's crack one open and take a look. Once these screws are out, both sides come right off. This round part is called the rosette. It's covering the inside parts of the door handle. It is fixed in place which means it will not rotate with respect to the handle. The handle always wants to be in the horizontal position. The spring is actually a stiff metal wire wrapped around right here. The wire is bent to the two ends. When I twist the handle, right here, either up or down, the spring gets tighter. As soon as you let go the handle springs back into place. Imagine if you didn't have the spring; your door handle would always flop to the downward position. The other side looks very similar. There's also a spring wrapped around the middle. You'll notice three metal bars sticking out right here. This one in the middle is called the spindle. And these two are the fasteners to part of the rosette. When I twist the handle, the spindle goes with it too. This part here, is called the latch. and the rest of this is called the latch assembly. If I push in the latch and then let go it springs right back into place. If we take a peek inside here you can see the spring that makes this work. I'm going to fade in pieces here one at a time. This is the transmission plate. When it gets pulled to the right, the latch also get's pulled causing it to come in. These two pieces are called the cam drive units. If they are rotated in just the right way they will push the transmission plate. Notice how they can be rotated either way and they will still push on the transmission plate. Now what would cause the cam drive units to rotate? Remember the spindle from earlier? It fits right inside the cam drive units. There's a cage that goes around all of these parts to hold them in place. Now, let's put this all together. Rotate the handle which also rotate the spindle, the spindle then rotates the cam drive units which pushes on the transmission plate which then retracts the latch. Now that's a chain reaction. This happens every time you open a door. So what happens if this door has a lock on it? After all, we don't want your younger sibling barging in without an invite. When the lock is horizontal, we can still turn the handle. But when the lock is vertical, I can no longer turn it. Inside the spindle here there's a hollow space for another metal piece to go through. This is called the driver. When we rotate this lock, the driver rotates with it. The magic happens at the other end. First off, let's look at the inside of the rosette. This circular piece is fixed to it. The handle has an open slot, so it can still rotate. Here's the pieces that make the lock work. There's a piece that's fixed to the driver. We'll call this the fixed cam. Rotate the driver, and the fixed cam rotates too. This second cam is facing the other direction. We'll call it, the sliding cam. Because of the extrusions on the top and bottom it doesn't rotate but instead can slide back and forth. When the door is being locked the rotating cam will gently push the sliding cam. When the door is unlocked a spring will push it back into its original place. The whole reason the door locks is because of these two notches at the end of the sliding cam. In the locked position, they slide right into these grooves on the rosette. If you remember from earlier, the rosette does not move. Now our handle is locked. But if we unlock it, The sliding cam slides back and we can rotate the handle again. Well I hope you now have a "handle" on how this works. My name is Jared Owen, thanks for watching.
