I have been refinishing floors for 10 years now and have had problems here and there but this one scares me.
On all my sand jobs I run the same thing on both my lagler hummel and super7, 50 grit and 100 grit, finished up with a 120 grit screen on my buffer.
But I helped a well established company for a day and they rough the field with the big machine using 36 grit, then they do all theyre edges with only 80 grit, then fine the field with 80 grit, and finish by buffing the whole floor with a 120 screen. floor looks great and only took half the time.
So I started using this technique but added palm sanding the edges with 80 grit on an orbital sander. first couple jobs went fine. But the last couple jobs showed a very faint picture frame on only a couple end walls but only a 1/4'' line about 4-6'' from the end wall. Im dumbfounded because I don't rush when fining off the field and my helpers palm sanded from the baseboards out 6''.
I always buff into my end walls, then buff my field at a 45 degree angle followed by going with the grain.
Any ideas how I can trouble shoot this?

Thanks

is the frame darker or lighter than the field?

One common mistake is to not change edger paper often enough. In a typical 10x12 room , I would use at least two to three pieces of 80 grit to fine off or four or five 100 grit .

If you let your papers go too far, they heat up, get soft and polish the edges of the floor. If that happens , a bugger isn't really enough to get the surface even with the field unless you spend a very long time working it .

If youre buffing at 120 and palming at 80 that could cause some differences.

Seems to me that the variable is the palm sander. I'm not a sander by trade, I apply 2nd and final coats...been doing it for 16 years, so take what I say with a grain of salt, as this problem piques my curiosity and I love to figure out flooring puzzles ( see my last post on dye stain ).

I've noticed when working with a palm sander that I can't get the same grade of sanding done by hand as a rotary disc edger can. I've tried for years to replicate it on jobs. I've tried to do touch ups on stain jobs where I had to remove sanding marks and all I carry is a scraper and a palm sander with various grits from 40 to 220. Even water popping rarely gets the same results as having a sander come back out and run the edger on it again.

So, perhaps if you have the option of having a small bedroom done where you only palm sand half of the end wall and leave the other untouched and then buff as usual, perhaps you will be able to see the results without it being obvious to the customer. This job is a lot of experimentation as you go along. I've personally evolved my coating techniques many times over to help me achieve a consistent, perfect finish every time and every circumstance. I got there by testing the limits of what I knew worked and what I thought could work.

Thanks for the replies.
I decided to try 120 grit easy change disk from 3M instead of Palm sanding or screening on my last sand job. It was 330 ft of red oak. The sanding disks with a 1/4" white pad on the 16" buffer eliminated the 80 grit edger swirls and the faint drum marks on end walls. They only last half as long and I used 2 disks on the 330 ft (1 for all my edges and 1 for my field). What I liked most about the disks is they don't dish out the soft grain like screens do.