Big grinder sanding backer pads

[Know Wosad]

I have both 7" and 9" Makitas that spend most of their life on the shelf.
I have some BIG **** to work on and am considering sanding disks over flap wheels because it's nasty work.I plan on the 7". The reviews on the Makitata pad talk about the nut getting in the way and, from pics, it does look like my avatar designed the nut. I see Boschmake a more commonly seen style that used a flat spanner nut to **** the disk in the center.
What do youz guyz use and whats a good grit for mill scale and medium rust. I generally use 40 and 60 on flappers and 24 to take down a weld but a flat disk is "different" ? Or no?
See what I mean ? Get that "engineer" a banana

 

[Superbec]

flat disk is so much faster than the flap .. 2-3 x faster

I built a bridge ~10m .. with a 125mm grinder, I believe your 7" will get old pretty fast but hei... maybe you like working out.

 

[Know Wosad]

If a 7" grinder wore me out I'd get into another game to play.
What brand of backer do you run on the 115 ? (thats forna harrf for us metrically challenged Amerkins)

 

[Superbec]

If a 7" grinder wore me out I'd get into another game to play.
What brand of backer do you run on the 115 ? (thats forna harrf for us metrically challenged Amerkins)

I got a Promat, don't know if you can get those in the U.S. but I must say the 3M is far better it has some ridges tfor cooling and the nut is flush... that makita is crazy
those things eat metal so fast I bet you don't need the 7"

 

[fourjeepin]

I use the Home Depot flat discs all the time in my 4-1/2". I tried flaps a few times, but they seemed to wear out really quickly.

 

[Know Wosad]

I was on a mission, as usual. I found some good options.
Chekkitoot !
Gonna call them after the rest of us chickens wake up and get a box assembled. 7", 4.5 and a shitload of different disks to try.Some Walter cool cuts and stuff.I'll let you girls know how it works out.Put some brushes and red grease in lo' bertha too.The old thing has been at it for a few years,,,,okay. Many few
http://www.weldingoutfitter.com/products/walter-15m007-turbo-action-pad-7-black-1-pack