Key head replacement

Made a basic replacement head for a friend whose flip key broke. I've tested it on a Kia flip key. The blade will be off center slightly but it isn't that noticeable. The fit was tight. I ended up filing it down on the edges of the blade to give it a rough surface and then used a torch to heat up the key blade. I then tapped the heated blade into the replacement key head and it doesn't move or wiggle. I tried to pull it out with my hand and it wouldn't budge. The key ring hole is a little close