angle grinder flap disk arbor bushing

[swimamile]

My angle grinder has a 5/8" arbor. I found some flap disks with 7/8" arbor hole. I have a reducer bushing that fixes this difference, but it came with a wet-dry blade, for concrete/masonry work. That masonry blade is flat, but the flap disk appears to have a slight offset.
If it matters, my grinder is a Bosch 1380 slim. The flap disk is BOSTITCH BSA8207M 4-1/2" x 7/8" Z60 T29, here:
http://www.ebay.com/itm/331379026057?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
BTW, I know I can get a 5/8" flap disk; these Bostitch 7/8" are just way cheaper.

 

[crewchief888]

the bushings i have are 2 sided, one side has a thinner "step" that the other side.

i use the thin side for cutoff disks, the thicker side for grinding wheels and flap disks.

 

[Advan]

I'm not understanding the problem.... Does the spindle nut not fit in the "cup" on the flap disk? Have you flipped the nut upside down?

 

[vettex2]

pics always help