I would work this problem in this order:
The printer - go into its settings and make sure the page margins are as you desire.
LR page setup - make sure the margins match the printer settings.
LR photo edit - make sure the crop of the photo matches the ratio for the page.
If you try to print an image cropped to 8.5x11 in a page 8x10.5, the resizing of the image to fit the page will create extra margins.
My thanks to all who replied. Much appreciated. I thought I had covered all the bases but the problem was in the Page Setup portion of LR. Somehow the right side border had been set incorrectly. I changed it to .25 and all is well.
Happy Holidays to everyone.
Glad you got it sorted out. I was going to suggest this, but your statement in your original post started me looking deeper!
...The smallest margins it will allow me to set are L,Top, Bottom = .25 and right = .56...
Looking back, I guess I was a bit vague. I was unable to change the margins under the Layout pane in the LR Print module. I was able to correct this by going into Page Setup.