After going through the manual for the HD-10, I learned that the terminals on the rear of the HD-10 could be used to attach a key. So off to the garage I went to put some terminal connectors on some wires to use to hook up the J-38 key to the HD-10.
It took a couple of tries before I figured out where the wires were supposed to go on the J-38. There are lots of pictures of J-38 keys on the internet, but not too many that show how the wires are supposed to be attached (the terminals are the two on the inside).
With everything connected, tapping the key made the keyer make noises and I managed to make some Morse Code sounding noises with the key. Now they can sit on the desk next to me so that I can practice tapping out Morse Code whenever I feel like.
I still need to take the key off the base and clean it up a bit, and then make up a cable that I can use to plug the J-38 into the radio with. Also thinking about seeing if I can find a nice block of wood to attach the J-38 key to for a more solid base and to elevate the key a bit.