Anecdotal Scotch-Brite grits?

M

Mr.Wizard

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Feb 28, 2015
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The question of Scotch-Brite equivalent grit keeps coming up and I think maybe it's time to add it to my grit chart. I have been unable to find any actual particle size values for Scotch-Brite, so all I can work with is "equivalent finish," and the tables I have seen for that really don't agree with each other.

Do any of you have your own experiential comparisons to P graded paper, especially the finer Scotch-Brite grades like the gray Ultra Fine 7448 hand pad?
 
SCOTCHBRITE GRIT CHART

7445 - White pad, called Light Duty Cleansing - (1000)

7448 - Light Grey, called Ultra Fine Hand - (600-800)

6448 - Green, called Light Duty Hand Pad - (600)

7447 - Maroon pad, called General Purpose Hand - (320-400)

6444 - Brown pad, called Extra Duty Hand - (280-320)

7446 - Dark Grey pad, called Blending Pad (180-220)

7440 - Tan pad, called Heavy Duty Hand Pad - (120-150)
 
I can try to explain my experience used mostly stainless blending and polish and some auto body paint and blending
White basically like they say cleaning ,it will barely scuff clear coat
Green close to 600 but wears quickly probably closer to 800
Maroon I use most of and it will blend a #4 stainless brush finish and close to 400 grit on paint
Dark grey also blend #4 stainless and closer to 220 when used
This is using 3M scotch brite brand ,many other knock off brands I have tried but do not hold up or even compare .
Hope this helps out.
 
I can only speak to the green ScotchBrite. The rated 600-800 for it, by the charts, seems pretty accurate as compared to equivalent grit wet/dry sandpaper (FEPA-P standard). I've used both on occasion, for cleaning up blades & bolsters (brass, nickel silver, SS).

Obviously, the harder or more wear-resistant the metal, the finer the effective finish produced by it will be. So the finish on a hardened SS blade would appear somewhat finer than seen on something like a brass/nickel bolster.
 
R rlucius They appear to be mostly consistent, but not common, and still confusing. Colors are not only by grade (grit, e.g. MED or VFN, as well as grain type, (A)lumina or (S)ilicon carbide) but by specific product, e.g. "7447 PRO" is red, and "General Purpose 7447" is maroon, but both are A VFN. Current hand pads only start at "MED" i.e. the "7440 - Tan pad, called Heavy Duty Hand Pad" mentioned above is A MED whereas there is a brown S CRS belt, not to be confused with the brown "6444 Extra Duty Hand Pad" that is A FIN. I can pull up some catalog images if you like.

Correction: No, they aren't consistent. Maroon is A MED in belts and A VFN in hand pads.
 
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I don't think scotchbrite is a conventional abrasive. It seems like it does some kind of combination of actions, which include abrasion, but also maybe burnishing? Or perhaps there is some much finer polishing action don't by the synthetic weave or something. I'm guessing at the causes of the effects I see when I use ScotchBrite on metal.

Scotchbrite seems designed for blending and "softening" finishes. There's a 3M video showing how to conceal weld lines using various abrasives, ending with ScotchBrite. It's pretty incredible. Oh well, let me look at up so you can see.


With that in mind, I think that the grits listed on this chart seem "close enough" for blending applications:

https://sharpeningmadeeasy.com/grits.htm#scotch

What I mean is, if you work on a blade with a 220 grit belt and you want to smooth and soften and blend the finish, then a medium Scotchbrite seems just about right. I have limited experience and I've only used ScotchBrite belts, not pads or anything else.

Brian.
 
ScotchBrite is a nylon mesh material impregnated with abrasive grit, like aluminum oxide, as mentioned earlier (* - see edit below). Effectively, the nylon mesh fiber is the binder for the grit. The compressibility of the pad tends to greatly soften the effect of the abrasive, which is why they won't be as aggressive as something like sandpaper or whatever. This is probably why they aren't generally rated by particle (grit) size, as the compressibility of the pad itself would render the finish much finer than actual grit size might imply.

Edit:
* - Reading more into this, the nylon mesh carries a hardened resin, which itself binds the abrasive particles.
 
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You can figure from the fact that I was browsing catalogs in languages I cannot read that my search got a bit obsessive, but it finally lead me to a chart in a 3M German brochure that provided finish equivalences to FEPA P for multiple types of Scotch-Brite products. This to some degree explains the divergence I see between other sources. It is still not unifying in the sense that there are many other tables that do not align with any of the types on this one, but I think it is the best I can hope to find and I shall conclude my search.

For the GLGC I shall take input from this table as well as several others, averaging values across sources and types. This all shall be highly approximate but I believe it is still useful information that is sourced as robustly as possible.

This is the table from 3M Germany, 2019.
gL1mKWt.png


Here I converted those values to microns and plotted them along with data from several other charts in official 3M publications. The leftmost column is my amalgamation guided by several lesser sources not plotted as well as anecdotal accounts including those provided above.
QlDd3iO.png

"A" and "P" columns for "WW" and "Swiss" sources are from tables that provided both ANSI and FEPA P values; as you can see 3M doesn't use quite the same translation I do, and interestingly if you look closely you will see that they use different translations between the WW and Swiss tables themselves.

The gold "UFL" value is based on this, with other influences:

eRfmj6J.png
 
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