So, what's been your experience with bucks hitting primary scrapes?
I understand that there are three types of scrapes:
random- just a random scrape
territorial- marks the bucks boundaries(ie.- field edges, cut-overs, etc)
primary- multiple scrapes within very close proximity of each other.

When do bucks tend to hitprimary scrapes during the pre-rut? Going to or from bedding areas or is it unpredictable?

I'll let you know what i see after this weekend. i found 3 fresh scrapes within 50 yards of eachother, so by your def these would be primary scrapes. i set my trail cam over one thats been in the same spot for the last 4 or 5 years, and i'll pull the card and see what kind of activity there was over the week. It'll be interesting, cuz theres a major cold front coming through the area thur-fri. btw im in north-central WI.

I found 2 fresh scrapes tonight, they were within 20yards of each other.
The one pictured is about 15yds to the left of a ladder stand I put up in late July.

The reason I'm asking is because I don't have a trail camera and I've found the mother load of scrapes and rubs. I've found about 10 scrapes and about as many rubs all within a 60 yrd diameter. My father-in-law was hunting in my stand last week and was busted by a 10 point. Although it hasn't slowed down the activity in the area. Unfortunately, I think this monster has gone nocturnal.

I believe most scrapes are made at night. I never heard of primary scrapes being defined as close to one another. Sounds as if you are in or close to his bedroom.
When they check them varies, they almost always will scent check them from a distance downwind so get your stand on the downwind side and hopefully you can catch him scent checking one some afternoon.

Normally this time of year the scrapes that we see mean absolutely nothing more than a buck stood there and scraped the ground. Nervous tension scrapes with no adgenda. Don't mistake these early scrapes with the ones that will pop up come late October. On occassion there will be a scrape that was used the year prior that will open up, but don't get too excited yet. You know that there was a buck there but, they're not hot. Unless you see evidence of urination and scat in them with the licking branch chewed all to hell and back, it means little to nothing.