This was my first try at building a real returning Mjolnir. But after this I wanted a more detailed version. If you want one that is full size and looks much more real then you should check out my new build at this link.

This project makes a great last-minute touch to make your Thor costume really come to life with a fun trick to make any party more exciting. You can actually throw it and (if you are worthy) it will come back to your hand.

If you have all supplies readily available you should be able to complete this project in around 2 hours.

Supplies

Materials

Pipe around 15 inches long and with an outside diameter around 1 inch
1 Retractable Reel Key Ring Example of Carabiner Style Reel with Key Ring
Foam block 3.75 x 3.75 x 7 inches
1/4 or 3/8th wooden dowl rod 4.5 inches long (need 3 this size)
Aluminum foil
Black or gray ducktape
Clear packing tape
Brown construction paper
Rubber band

Tools

Knife to cut foam and pipe with
Hot glue gun

Step 1: Overview

Check out the prototype and final product pictures to get an idea of what we are working towards

Step 2: Handle Return Mechanism

You need the hot glue gun hot for this step. Get your 3 dowl rods and put them around the key reel to hold it securely to the PVC pipe. This arrangement may differ depending on what housing your key reel has. As you can see in the images I had to work around the clip on the back of the blue housing. Put lots of hot glue on this to hold everything in place. But be careful not to glue string or the part that needs to more with the string as this will make it not return properly.

Step 3: Decorate the Handle

I started by wrapping duct tape around the pipe. Start it at an angle and it should naturally cover the length of the pipe as it wraps around. I used a technique where once I got the tape started at an angle I was able to hold the pipe in the air at an angle letting the roll hang. This made it easy to apply the tape without wrinkles by simply rotating the pipe.
I then covered the seam of the duct tape with brown construction paper in the same manner
Then the whole tube is covered in clear packing tape to hold the paper on and make a smooth holding surface. I applied this with the same technique as the duct tape.
Finally, I hot glued a 1-inch wide strip of aluminum foil to the base of the handle to make a nice edge. Once glued on just form the bottom around the rounded edge of the key reel.

Note that you need to also cover the key reel the same as the pipe so that it all looks like one continuous handle.

Also, note that you don't need to cover the whole length of the tube as some of it will be inside the silver foam part. Only around 12 inches will be exposed.

Step 4: Make the Hammer Head

Cut a piece of foam to the dimensions of 3.75 x 3.75 x 7 inches.

Now cut a 3/4 inch chamfer on all four edges that are 3.75 inches long (Not the 7 inch sides)

You also need to cut a hole in the center of the foam big enough to get the handle to fit inside. I would not suggest going all the way through but most of the way so that there is plenty of attachment surface area. (around 3 inches)

Now get a piece of aluminum foil about 18.75 inches long. Place the hammer in the center of this and wrap it around like a gift. There should the two layers on the bottom where the handle attaches. Now cover this in clear packing tape to prevent ripping the foil later.

Finally put a hole through the foil so that the handle can be inserted in the foam hole.

Step 5: Put It Together

Take the handle.
Put hot glue on it around the surface that will be inserted in the foam.
Insert the handle in the foam
Let the glue cool

Step 6: Finishing Touches

Put the rubber band on the cord reel and your wrist so that when then the hammer is thrown the cord pulls the hammer back to your hand. The best location to place the attachment is on the palm side of your wrist.

Your Mjolnir should be complete. It will take some practice to throw the hammer and successfully catch it again (do this before breaking something at the party).

You can use other things such as leather to make the handle and wrist strap look more authentic. But keep in mind that any changes in weight will change how the hammer handles when it is thrown.

Don't forget the rest of the costume!

Enjoy being the highlight of the party!!!