[fleetsidelarry]

I was using some 3-M Tri-M-Ite, 600 grit to wet sand some base coat work, ran low and found some 3-M Imperial 600.

The Imperial blew thru the base coat like it was 320 or 400. it is noticeably coarser to the feel, althought, of course, I didn't check it at first.

on the back, the Imperial is called a "production" paper and I noticed that the number was p-600, versus just 600 on the Tri-M-Ite. I thought the "p" referred to "production". Apparently, that's incorrect.

If the google search I did is correct, the Tri-M-Ite is manufactured in the USA (and/or maybe Canada) and is classed by our standards (CAMI) while the Imperial is non-USA and classed by european standards (FEPA), thus the "p" designation.

Can anyone verify this for me?

[tech69]

not sure but what the "P" stands for is not why you broke through the basecoat. I would put more focus on the work rather than the letter "P" thing.

I think it's just EU nomenclature for blah blah blah. What's more important is if sand paper is open or close coated. Ever try really cheap 36 grit where the grits fly out? That's open coat and is an issue. If you're using 600 "P" doesn't matter one bit. 600 is safe either way if it happens to be a tad grittier or smoother. Both of those 3m lines you mention are probably good either way, unless it's made for wood or something not steel.

[35prog]

You are correct in the classes of paper. the p paper cuts faster the grit is sized by different grades. Anything graded 400 or finer. Base and clear should cover it fine.

[jcclark]

Here's a chart

[fleetsidelarry]

thanks guys. yes, that's the same chart I found, interesting that my tri-m-ite 600 is equivalent to 1200 grit Imperial!

[jcclark]

I think you have some old paper,
They both come in "P" numbers now.
I don't think I've see any with the old style "cami"
grit scale in the last couple of years.
They've pretty much all have gone to the "P" (metric) scale.

[fleetsidelarry]

you're absolutely right, the paper is probably 3 or 4 years old. thanks again