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Should I use 400 grit

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Forum topic by Patrickgeddes14 posted 10-15-2019 09:40 PM 429 views 0 times favorited 14 replies Add to Favorites Watch
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Patrickgeddes14

193 posts in 351 days


10-15-2019 09:40 PM

I’m doing a bench with roughsawn spruce. I want to keep the roughsawn look is 400 a good choice to prep for urethane?


14 replies so far

View Axis39's profile

Axis39

80 posts in 132 days


#1 posted 10-15-2019 10:25 PM

You mean just hitting the rough sawn surface with 400 grit? Not sure it would do anything, other than lighten the very tips of the rough surface. Any sanding of rough sawn surfaces has always messed up things more than fixed it for me.

If you want to maintain the rough sawn surface, but make it a little less rough to the hand, I’d just plan on a lot of coats of urethane. Once you have a few nice coats fo urethane on, then, you can begin sanding a little to smooth the surface off.

You could also try epoxy?

-- John F. SoCal transplant, chewer uppper of good wood

View John Smith's profile

John Smith

2044 posts in 698 days


#2 posted 10-15-2019 10:31 PM

Patrick – try 360 and work backwards until you get the look you want.
360 – 320 – 300 – 220 – 200, etc.

.

.

-- I am a painter. That's what I do. I paint things --

View Andybb's profile

Andybb

2149 posts in 1139 days


#3 posted 10-16-2019 12:24 AM


Patrick – try 360 and work backwards until you get the look you want.
360 – 320 – 300 – 220 – 200, etc.
- John Smith
Interesting idea.

I’ve always lived by the idea that anything finer than 220 impedes penetration of the finish coat. Then sand that to 400 or higher if you want.

-- Andy - Seattle USA

View Lazyman's profile

Lazyman

4080 posts in 1923 days


#4 posted 10-16-2019 12:43 PM

I assume that the main purpose is to remove any splinters that might be a problem. I would work my way up to 180 or 220 just like you normally do with sandpaper, just don’t sand long enough to remove any mill marks you want to remain. I would not use a sanding block or power sander and instead of sanding with the grain, sand in the direction of the mill marks. It will probably only take a few strokes on each spot with each grit to get the look you are looking for.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View ArtMann's profile

ArtMann

1441 posts in 1351 days


#5 posted 10-16-2019 01:34 PM

400 or 320 grit won’t do anything of any value. I don’t agree with working backwards to coarser grits. You may as well just start with the most coarse grit you want to sand to. The end result will be the same. If I were you, I would do some experimentation with scrap before doing anything with the actual project. You might find that no sanding at all is what you want. The finish alone will smooth the project to some extent. On the other hand, you may find that sanding to 220 grit provides the effect you want.

View pottz's profile

pottz

6639 posts in 1520 days


#6 posted 10-16-2019 02:02 PM



400 or 320 grit won t do anything of any value. I don t agree with working backwards to coarser grits. You may as well just start with the most coarse grit you want to sand to. The end result will be the same. If I were you, I would do some experimentation with scrap before doing anything with the actual project. You might find that no sanding at all is what you want. The finish alone will smooth the project to some extent. On the other hand, you may find that sanding to 220 grit provides the effect you want.

- ArtMann


ditto.

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

View Bill_Steele's profile

Bill_Steele

591 posts in 2267 days


#7 posted 10-16-2019 02:12 PM

I would think for a rough-sawn look maybe just clean the surface and then apply the urethane. Perhaps a handheld wire brush or stiff nylon bristle brush.

My guess if you were to use 400 grit paper with a stiff backer on a rough-sawn board—you would end up slightly smoothing just the high points. 400 grit is so smooth that I think it polishes more than anything.

It might be interesting to experiment by using a soft backing pad (maybe use an intermediary/interface pad) with around 150 grit on a RO sander. My guess is that the softer pad will allow the paper to better conform to an uneven surface and will smooth more of the surface, but not flatten the peaks.

View Lazyman's profile

Lazyman

4080 posts in 1923 days


#8 posted 10-16-2019 02:21 PM

Perhaps using one of those sanding sponges to lightly scuff the surface might do?

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Rich's profile

Rich

5001 posts in 1125 days


#9 posted 10-16-2019 05:15 PM

A product like Mirka Mirlon Total would do the job very well. It not only will follow the contours and not flatten the saw pattern, it will also flag any areas that would snag clothing due to its nonwoven construction.

View WoodenDreams's profile

WoodenDreams

791 posts in 446 days


#10 posted 10-17-2019 02:42 AM

I’d would then probably take 120grit and take about six back and fourth swipes with the sanding block. will knock down some of the roughness, if still too rough, do another six quick back and fourth swipes.

View Zonker's profile

Zonker

100 posts in 386 days


#11 posted 10-17-2019 10:20 AM

I have had pretty good luck with careful handplaning. Set the blade to take a very thin shaving and the take the high spots down. I have some really old Barn siding that I’ve done a few projects with that I wanted to save the rough sawn look. By running a plane lightly over it, I’ve been able to knock down the high spots that might snag things and still keep the saw marks intact enough to see. The first few passes yielded “crumbs” of wood from the nubs and tear out left by the saw. As I progressed, I would get small broken shavings. I inspected the grain after each pass until I reached a point where I didn’t want to lose any more marks. And once the top coat of poly is on, the marks were even more pronounced. ope this helps.

-- Larry A. - I've made a small fortune with my woodworking. The trouble is, I started with a large fortune.

View Jack Lewis's profile

Jack Lewis

502 posts in 1613 days


#12 posted 10-17-2019 01:56 PM

I have had very good luck using a scotch brite scuffing ball in a drill motor on live edges and cut edges. They come in different grits also but not 400 grit.

-- "PLUMBER'S BUTT! Get over it, everybody has one"

View Lazyman's profile

Lazyman

4080 posts in 1923 days


#13 posted 10-17-2019 03:14 PM

Seems like the Scotchbrite and Mirka pads would snag on the rough surface?

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Rich's profile

Rich

5001 posts in 1125 days


#14 posted 10-17-2019 03:50 PM


Seems like the Scotchbrite and Mirka pads would snag on the rough surface?

- Lazyman

Well, that was kind of the gist of my post—if it doesn’t snag, you’re there, and the pad will smooth the surface to be ready for finish. It’s definitely not how to start off with splintery wood.

Unlike the 3M pads, the Mirlon Total are impregnated with abrasives and behave much like sandpaper. They come in equivalent grits of 360, 800, 1500 and 2500. The link I provided was to the 360-grit product.

I’m not knocking the sponge pad idea you posted, just sharing how I work.

I use shop-made blocks with the hook side of industrial velcro when I’m doing a flat surface to keep it even.

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