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Locksmith Tip: How to Make a LFIC Control Key

When customers call and set up rekey jobs, we always try to get all the information we can to make sure that we can be the most prepared when we get there. We're asking about how many locks they are or what your key says on it, all the bunch of different information that will get us prepared. But what happens when you show up and then your customer said they had a Schlage on their key, but you show up the cylinders are LFIC, the Large Format Interchangeable Core. What happens if you don't have the right control key, or what happens if you don't have any control keys?

 Large Format Interchangeable Core

I will show you how you can easily make a temporary control key so you can get the cylinders out and you can get the job done, but after a brief overview, in case you're not unfamiliar with LFIC cores. 

The Large Format Interchangeable Core will use your standard Schlage lock. You're going to use your standard Schlage keys. And as a comparison to a Small Format Interchangeable Core here, this uses an entirely different key, a different rule for pinning, and pretty much everything is different. You can also notice the size difference in the cylinders.

 Large Format Interchangeable Core

In LFIC, the cylinders use a normal SC4 key to operate them, but you must use a control key to get the cylinder out when it comes to rekeying them. Unlike the SFIC control key, the LFIC uses a specialized key. Below are two keys SC4 keys. The SC4 key at the top is the standard key, while at the bottom is the SC4 key control key. The difference is the little piece sticking out at the end. And what that does is that it will activate the little pin on the inside of the lock to open it up, to be able to pull the cylinder out. 

 standard SC4 key and control SC4 key

In a closer look, as you turn the control key for LFIC, this little piece will sink, and then you can pull the cylinder from the lock. So that's all the control key does; it has the same cut as the working key or a master key. The cuts are identical, but they differ at the little n piece at the end part.

 Large Format Interchangeable Core


It's always easier if you have the right control key to do the job. Still, in the real world, there's going to be situations where you're going to encounter a kind of bizarre keyway, or maybe you're just not prepared to do the job, and it's still essential to help your customer out and get the job done.

So what do you do when you go to the job without a control key to use? That's the big question, but all you need is a standard working key, then modify it to work as a control key.

On a control key, you're going to see this nice little bump at the very end. This part turns the pin that holds the cylinder into place.

 Control key

And to turn the standard SC4 key into a control key, you need a permanent marker to draw the line at the very bottom to help us cut.

You can see that I went from the very top of the groove and drew a line. It is because we do not want to cut less than where the black marker is. Even a little above it will be okay, but that helps when it's on the key machine to help us get the proper depth down. It seems to all work as long as you don't get in and hit that black line there.

 cut a standard key into a control key

Get on the machine and put the existing key into the left and the key with the permanent marker line on the right. Line them up like usually cutting a key.

After you do that, on the side to where the existing key is, loosen up the jaw. Take another key, and you're going to stick it in, just like this and create a gap.

 turn the standard SC4 key into a control key

We're going to do the skinny side of the blade, the blade part that gets cut.

 cutting a standard key into a control key

You can see there's a gap right here, between where the key is and where the shoulder stop is. That's going to be the gap in the distance we need to get that little bump piece at the end.

 How to make a control key

We are now ready to cut the key.


While cutting the end of the key, make sure to stop before you hit the black line.

 turn the standard SC4 key into a control key

Once done, flip the keys to cut the other side, and we must extend out the bottom shoulder. So, we're going to do the same thing, flip the keys upside down, get the shoulder stop put up to get them aligned. I'm going to loosen up the existing key then take another blank key to create the nice little gap again. That way, both sides will be equal—time to cut.

We have done now because we brought the shoulders back just a little bit so we can create that little bump at the end, that little cut, so it's going to grab that little pin and pull it in so we can get the cylinder in and out.

 turn the standard SC4 key into a control key

Buff the new cut control key, get the lock and try to pull the cylinder out.

 removing cylinder from LFIC lock

By making that little bump at the end will allow us to get the cylinder in and out. So that's how you can make a control key for LFIC Schlage locks on the fly. Thank you, and hopefully, this was helpful; we'll see you next time!

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