This is a water pump for drill. You could use 4х120mm nail or something like this for creation the shaft for this pump. As example i used the nail.

Assembly steps:

1. cut off the nail had
2. cut 10 mm nail piece and weld it to main nail piece to make shaft key
3. put the shaft in impeller hole and close it with the impeller lock
4. put the grease into the friction pairs in the pump caps (i used washing mashine bearings grease)
5. assemble the pump, use grease or sealant to seal case-caps connections
6. use little screws to connect caps to pump case