Coarse wet dry sandpaper

[oilboy123]

Is 120 grit considered the most coarse grit of wet dry?

 

[Stu_Rock]

McMaster has it going down to 60 grit.

 

[Kestas]

That depends on what you're trying to accomplish.

 

[oilboy123]

General wet sanding of metal....different uses in that area though.

Don't think that I have ever seen lower than 220 locally.
Is this waterproof stuff the same as the Wet dry that you buy in parts stores?



Aluminum Oxide Cloth Sanding Sheets
The most popular choice for general purpose sanding of metal and wood. All are 9" x 11".
Dry Sheets— 36-60 grits have a strong, stiff backing; 80-500 grits have a flexible backing.
Waterproof Sheets— Unlike dry sheets, these products resist water as well as grease, chemicals, cutting fluids, and other solvents that may be present when sanding, deburring, cleaning, or polishing. Backing is flexible.
Sheets
Pkg. Pkg.
Grit Qty. Per Pkg. Qty. Per Pkg.
Dry Sheets
36 25
4671A23 $37.43
5
4671A79 $10.51
40 25
4671A22 33.61
10
4671A78 14.67
50 25
4671A21 30.98
10
4671A77 13.78
60 25
4671A59 28.81
10
4671A76 12.73
80 25
4671A58 24.48
10
4671A69 10.64
100 50
4671A17 45.12
10
4671A68 10.00
120 50
4671A16 45.39
10
4671A67 10.00
150 50
4671A15 45.39
10
4671A38 10.00
180 50
4671A14 45.39
10
4671A37 10.00
220 50
4671A28 45.39
10
4671A36 10.00
240 50
4671A13 45.39
10
4671A35 10.00
280 50
4671A27 45.39
10
4671A34 10.00
320 50
4671A12 45.39
10
4671A33 10.00

Pkg. Pkg.
Grit Qty. Per Pkg. Qty. Per Pkg.
Dry Sheets (Cont.)
400 50
4671A11 $45.39
10
4671A32 $10.00
500 50
4671A26 47.90
10
4671A31 10.19
Waterproof Sheets
60 50
8270A58 52.39
10
8270A78 12.53
80 50
8270A57 48.46
10
8270A77 11.76
100 50
8270A56 45.94
10
8270A76 11.25
120 50
8270A55 45.94
10
8270A75 11.25
150 50
8270A54 45.94
10
8270A74 11.25
180 50
8270A53 45.94
10
8270A73 11.25
220 50
8270A31 44.61
10
8270A32 10.99
240 50
8270A52 45.94
10
8270A72 11.25
320 50

 

[labman]

You can also ''wet'' regular sand paper with mineral spirits.

 

[Kestas]

I use mostly silicon carbide paper for grinding metal in the lab. Again, the grit depends on what you're trying to accomplish with the metal. For general sanding, you shouldn't need anything finer than 220 grit. 120 to 80 should accomplish most tasks.

For wood, 120 grit would be considered fine grit.

Using the paper wet will keep the paper from loading up and increase the life of the paper.

 

[TooManyWheels]

I used 30 grit wet/dry for years on body/paint work, and I think I have heard of 24 and 18 (I don't keep up with this anymore).

 

[Kestas]

30 grit??... that would leave a similar finish as putting a foundry grinding wheel to the body panels! Maybe to hog off bondo perhaps.

 

[TooManyWheels]

I'm not making assumptions on his use. I'm just answering his question as it is stated.

If his intended application is to reduce Bondo or remove paint, 220 isn't going to do anything.

 

[oilboy123]

I see one website with Silicon carbide 60 grit. Where can you find course 18-60 grit silicon carbide without mail ordering it? I am thinking of using it to sand salt corrosion on a galvanized boat trailer.

I was thinking I could keep the dust down by using it with water. Prepping the parts dry is very nasty. I am going to get a quote for a company to sandblast the trailer parts. If it's too high I will do it myself.

 

[TooManyWheels]

Body and paint supply places will have it. You might also think seriously about using silicon carbide sanding disks and/or a wire cup brush on a 7" grinder. If your wrists can handle it, it will take off rust, now!

 

[oilboy123]

I did not know there where Silicon carbide sanding disc? I thought about the wire cup grinder.......

What I am really trying to do is not remove the base metal. Maybe the wire cup would do that best?

I see this sort of thing, but it has internal thread. The sander I have has an internal thread with a angled Allen bolt.
So I believe I would need a grinder type sander.

Makita 743209-B
2-3/4" Knot Style Cup Brush - Stainless Steel Wire

 

[TooManyWheels]

Yes, that Makita item is the kind of thing I'm talking about. Assuming the rust is not all crusted up/scabbed over, the cup will get it clean and not hurt the metal. Carbide disks will do pretty much the same, assuming you don't spend much time in one spot. If you do, you can start to reduce thickness.

You could rent a grinder, and the rental place may well have the cup brush or disks also.

 

[Kestas]

Sandblasting is a more elegant way to remove rust from a trailer. It removes rust from the nooks and crannies that are difficult to reach by grinding or sanding. Sandblasting is not too aggressive on the metal.

 

[oilboy123]

The material thickness is .100 I assume that it is 13 gauge then dipped in the galvanizing get's a little thicker?

The tool rental is not a bad idea. I have not rented a tool in a long time. Took some pics and am getting a quote for sand blasting. Then I will make a decision.

My Brother told me I could do painting/sanding at his place of work. Makes me wonder if I could rent or buy a sand blaster and do it to it. I see Harbor Freight has a pressurized model. I would have to tent off the room and rent or purchase a sandblaster, and breath through a respirator. Then maybe practice on a test piece.

 

[Kestas]

Few mills dip their steel in galvanize. Most of it is electrocoated and rather thin. If it was indeed dipped, then it was a quality steel product before it rusted. I believe welding galvanize is difficult.

 

[oilboy123]

The trailer is a 1985. I assume it was hot dipped in galvanizing?

 

[Kestas]

Probably not. Only a trained eye can truly tell. Dipped would leave a somewhat uneven surface.

 

[oilboy123]

I would assume it is because of drips I see on the parts.

 

[Kestas]

Yup, that's hot-dipped!