I was browsing around on instructable's and came across reconscious Friendly Folding Keychain https://www.instructables.com/id/Friendly-Folding-Keychain/ and liked what he had done and wanted to make my own version with the keys I had but slightly modified it so I could use it with my carabiner that I have to keep them on a belt loop.

Step 1: The Keys Housing and Other Materials

Some of the Instructable's I had seen were using a bike tool for the keys. I was able to find a cheaper version at harbor freight for around $5 that was for hex keys. it was easy to dissemble and had plenty of spare parts to use as well. You will need some additional pieces of hardware to:

Washers (some that will fit around the shaft of the housing)
rubber grommets (same inside diameter as the washers above)

We will cut the grommets in half and use them as a buffering and tension pad against the housing when we are putting it together

Step 2: The Keys

First thing to do is decide on what keys you are going to be putting into the folding key chain. I am using three house keys and two car keys on mine. As you can see I went and got copies of all of the keys before hand, I did not want to take a chance of messing up the origionals in case i needed them in the future. You may see the last key as familiar if you have seen any of my other instructable's. It was an RFID key I had to make a (cheap) copy of without the RFID chip just to unlocked the doors, you can see the instructable here: https://www.instructables.com/id/RFID-Key-Copy/

Step 3: Modifying Them

What we want to do is cut the keys so they fit in the housing without any bulk on them. For this we will need:

A Bench grinder
A Dremel tool with cut-off disk
Some small Files
A drill bit (I used a 1/4" bit)
a de-burring brush

Drill a hole into the key where I wanted the shaft of the housing to pass through.
Trim the sides of the key down with the Dremel using a cut-off disk.
Round the edges with the grinding wheel.
Then de-burr the key so it has no sharp edges when we have cut and ground it down.

Wash, rinse, and repeat for the remaining keys

Step 4: Making a Key Ring for It.

Remember the metal piece I mentioned we would elaborate on further in step three. Here is how it is made. Originally it was a leftover piece of metal from some other project with a 90º bend in it and a screw in one side of it.

Take the bend out by removing the screw and stretching it into a semi-flat strip.
Then I placed it on one end of my sledge hammer and pounded it flat with a regular claw hammer.
After it was flattened I rounded the corners smooth with the grinding wheel.
Then drilled a 1/4" hole in one end and de-burred the whole thing.

Now we have a place to add a key ring to it to add additional things.

Step 5: Putting It All Together

Now we just need to make everything fit together. There were 3 different sizes of plastic washers that came with the hex key set: I will list them as the following: #2 is the thickest washer it should have come with 2 of them, #1 there is one of them and it is 1/2 the thickness of a #2, and #0 there should be 8 of them (they are very thin). I tried to put a plastic washer between all of the metal parts to reduce friction and fatigue on the adjacent keys. The exploded view is stacked as follows going from top then-left-to-right:

Top:
Shaft screw, housing piece, #2, #0,#0,#0, H KEY, #0, Washer, Key Ring, #0, H KEY, #0, H KEY, #0, rubber grommet 1/2, Housing piece, end screw.

Bottom:
Shaft screw, housing piece, #1, C KEY, #2, Washer, C KEY, #0, rubber grommet 1/2, Washer, Washer, rubber grommet 1/2, Housing piece, end screw.

The reason it is in the order it is, is because we need the keys to slid between each other when we fold everything together. This is the order I came up with to have everything mesh nicely.

And you are done. This works well for elderly people who need some extra strength when using keys, just make sure you do not turn it too hard or the key could break in the lock, they are not fun to remove when broken.