Swing Arm Axle
The swing arm axle is made in two pieces.
On one side there is a 6mm Allen head cap screw that threads into the other half of the axle. On the other side there is a 10mm Allen "relief" cut into the axle half itself.
The two axle halves fit into each other, frequently rather tightly. If you back the 6mm bolt out part-way, and tap the head of it with a punch and hammer, (or use an 8 - 10mm bolt in place of the punch if you don't have one,) the impact will usually separate the axle halves and loosen one side enough for it to be removeable by hand. Rotate it and pull on the flange to work it out of the axle tube on the frame.
No need to hit it hard, a tack hammer tapped lightly on the bolt head a few times will usually do. If you hit it too hard, you will distort the bolt threads or bend the bolt. This is Not Good.
Best,
Doug