Re: 8 year old Chehalis apple not fruiting, Hillsboro OR
According to the list at the link above, Chehalis flowers early (does this comport with your observations). It may be blooming before the others. None of Melrose, Red or Golden Delicious are listed as blooming in the same group and Gravenstein is a triploid and pollen-sterile so wouldn't serve as a pollenizer.
So problem #1 could be that you don't have a pollen donor.
Problem #2 could be that an early flowering tree is more likely to be succeptible to frost damage (although, at least here, this year seemed great for apples).
Problem #3 could be that an early flowering tree may finish its bloom before pollenating insects have emerged and begun their activities.
Problem #4: none of those earlier things are relevant if the tree isn't flowering sufficiently, which you've noted. That could be related to pruning. Or I've heard that excessive vegetative growth can also cause that (happens sometimes when trees are in a lawn that is being fertilized and watered). Your watering doesn't sound excessive. How much is the tree growing each year?