PSA discs--- 3M vs. Mirka vs. Norton

[Nathan Hawkes]

First off, I'm a semi-production turner, mostly green wood bowls. I use shop-made soft foam mandrels which conform well to curved surfaces. I go from low to high, starting wherever needed to at least 400grit, sometimes higher depending on the wood species. I'm about ready to make the switch from 3 1/2" velcro discs to 5" PSA discs for most of my medium to large bowls. Larger discs sand faster and are more economical. There are quite a few choices out there for PSA. I'm not completely sold on some of the "extended life" discs that I've used, for a couple reasons--cost, and they do LAST much longer, but don't seem to cut as fast or consistently as when brand new.

What are you using, and why? I've heard good things about both 3M and Mirka "gold" lines. 3M is "stikit gold" and Mirka is "bulldog gold". Both are semi open-coat, non-loading, stearated, aluminum oxide abrasive on lightweight, probably A-weight paper. Mirka also has another product, "Carat" PSA discs, which seem to match the same description, but cost less. Norton makes a "dry ice" ceramic/al-ox disc that is supposed to last a long time, but costs a LOT. 3M makes a similar "cubitron" disc, which seems to be even more expensive.

Who uses what abrasive, why, and what are you sanding (size, shape, etc). There aren't a lot of PSA users out there that sand in the amount that I want to hear from. Thanks in advance!!

[Kyle Iwamoto]

I use Indasa discs or Norton A275. Pretty economical. They last a long time. The Indasa is my favorite, I think they have the best quality control on grit size. They are both light colored, so in the event that a grit breaks off and gets imbedded in your light colored wood, it won't be visible. In dark wood, you won't see a light grit in there. But you will notice a black spec on maple. After you apply finish of course.

Just my $0.02.

[Reed Gray]

I haven't talked to Mike Mahoney about abrasives in a while, but he swore by the 3M purple ceramic discs, PSA, and only up to 220 grit. I tried one, and it was fine, but I never liked the idea of PSA in a dusty/debree cluttered bench and shop like mine. Fine if you use the disc for a moment or two, then toss it, but horrible idea if you can use a disc for several bowls, like the blue discs from Vince, or the ceramic ones from 3M.

On a side note, I found out a while ago that for the coarser grits, up to 220, that they cut far better (120 on a firm pad cuts better than 80 on a soft pad) with a firm interface pad. Vince does sell a medium pad which does conform better to inside transition areas. The soft pads are fine for 320 and above. I don't know if Vince (VincesWoodNWonders) could make you custom interface pads or not. I do love his firm pads with the 1/4 round profile on the edges. Only place I have found that carries the 3M ceramic ones is the Sanding Glove.

robo hippy

[Bob Bergstrom]

I've used the 3M ceramics and have to say they cut the best and longest of the disks I've used, but if you are changing PSA disks there is always the problem of keeping them clean.

[Nathan Hawkes]

Good points all. I found the indasa paper was not very consistent in grit size from order to order. In regard to changing the discs; I would have a separate mandrel for each grit so that I would not have to change discs except to change out to a fresh one when spent. My shop is also quite dusty and full of debris. The lack of higher grit availability makes the 3M less attractive than others available. I like the pink discs from Vince, but the lower grits have been sold out for a while on his site.
Reed, thanks for the hints on the mandrel firmness-I may try making some firmer ones out of a higher density of foam. I just have to find out where to get the foam....
Anyone else out there using PSA??

[Bob Bergstrom]

Good points all. I found the indasa paper was not very consistent in grit size from order to order. In regard to changing the discs; I would have a separate mandrel for each grit so that I would not have to change discs except to change out to a fresh one when spent. My shop is also quite dusty and full of debris. The lack of higher grit availability makes the 3M less attractive than others available. I like the pink discs from Vince, but the lower grits have been sold out for a while on his site.
Reed, thanks for the hints on the mandrel firmness-I may try making some firmer ones out of a higher density of foam. I just have to find out where to get the foam....
Anyone else out there using PSA??

I found the foam from the sole of "flip flops" work very well for firm mandrel pads. Xl sizes will yield a pretty big disk but short of 5". I've also used stadium cushions, solid rubber balls and garden kneeling pads.