Step 1: What You Need to Get
If you want you can use a magnetic bit extension instead of the quick-change one, the method to make is still the same.
Step 2: Making the Handle
Place a mark in the center of the handle.
Drill a 1/4in hole in the center of the handle.
To make drilling into a round steel bar easier you want to score the center with a file and center punch it. (sorry I don't have pictures)
Once the hole is drilled you will need to file the hole to a hex shape. You will want the hole to be slightly smaller than the hex portion of the extension.
Step 3: Attach the Extension
Now, very carefully, center the handle over the hex extension and pound on with a hammer.
Once the end of the extension reaches the other side of the hole in the handle use the deep socket over the end of the extension to push down the handle.
Use a grinder or file to file off the end of the extension poking through the handle and to smooth the ends of the handle, removing any sharp edges.
Tip: Use a piece of scrap 2x4 to make a stand to hold the bit extension. A smaller hole is drilled all the way through, just big enough for the bit. Then counter sink with a hole just big enough for the extension. Make sure that when the extension and bit are in the holes the bit sticks out just a little bit (1/8" or less). Place the extra bit in it to keep the head of the extension protected and then place the extension in the hole. The first one's I made I didn't do this and I damaged the Quick Change adapters.
Step 4: Your Done!!
Coat the handle in Tool-Dip for a professional appearance.
I've also included a picture of a smaller pocket version I made with a 4" handle and a shorter bit driver. Perfect for throwing in a glove box or with a bicycle tool kit.
The nice thing about the quick change adapter is there is a ton of cool bits you can find to put in here beyond just screwdrivers. I recommend checking out the Kobalt Speedfit system for some cool bits.