What you are seeing is the effect of poser smoothing. If the ends of a cylinder are not visible you can simply delete the polygon , otherwise unweld it . The square part of the hammer can be improved by small bevels along the edges, or unwelding . 

Changing the crease angle should fix the problem in poser 7 , but you will need to play with the settings , try 30, 45, 60, 80, 120, 160 degrees and see what happens to that mesh .  Turn smoothing off is an option too. In some cases you want smoothing on but parts of the model need sharp edges, That is a matter of small bevels and selected unwelds .

Splitting vertices is an unwweld but unwelds everything so may be overkill. Learn to be selective.

Nice BIG hammer by the way .