Shaft snapped off
You have to disassemble both the top and bottom. The planetary gear rotates on the shaft and has retainer bearings to hold the bottom together. The top has Springs, gears and shift collar that are keyed and the keys have to come out before removal. Have fun.
I was able to find that this is a Presto unit. Are we talking about the Presto PM-20 mixer as shown in this link?
Please let us know, so we can better assist.
It appears from the diagram in the above link that the Working Shaft is removed from the bottom of the operating shaft, though it is hard to be certain from this diagram. But the flat key at the top of the working shaft is making me think it goes in from the bottom.
As far as pressing or hammering, I cannot say with certainty. Hopefully another user will have some insight.
Retrieving data ...