Trying to make a gear pump

[Futterama]

Hi forum,

I'm new here but have been reading alot about your fine projects.

I have a small lathe and a small vertical mill and wanted to build a gear pump, later some valves and cylinders, just for fun and maybe it will end up with a wheel loader build of some sort.

Anyways, I have these module 1 10T gears I want to use for the gear pump. The flange section has to go for the gear to be used in a pump. Now how do I fasten the gear to the axle without the flange to drill and tap for a set screw?

The gear has a 4mm hole, the axle is a 4mm surface hardened pin.

Please advise :-)

Thanks.

Best regards,
Martin from Denmark