Newbie - How fine to sand for paint? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 9 Old 03-29-2020, 03:39 PM Thread Starter
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Newbie - How fine to sand for paint?

Hi All

I've made my baseboards and door trim from poplar and have planed to 7/8 and sanded it to 3/4" with an 80 grit paper on a drum sander.

It feels pretty smooth to my hand and it looks good but I don't know if I need to go over it all again with a finer paper or not.

I plan to prime and paint it with an oil based paint.

Do I need to go further with the sanding? I'm a little concerned that if I start trying to smooth it with a palm sander I'll lose the evenness that the drum sanding produced. I could put a higher number paper on my drum but I don't want to do more work than is required, if it will come out smooth with a coat of primer and two coats of paint I will stop sanding now.

I'm open to suggestions, I've got about 300 linear feet milled so I don't want to make a mistake at this stage that causes me to have to start over.
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post #2 of 9 Old 03-29-2020, 05:54 PM
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I would no stop with 80 grit. Even though it feels smooth to your hand, it could show when you get it painted, especially with white paint. I would sand to at least 120.


George
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post #3 of 9 Old 03-29-2020, 07:02 PM
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why on earth sand off 1/8" after planing it? Just because you can?

In any event, I would never stop at 80 grit, if the 80 grit had been cutting like it should.

For me, 80 grit is used only ocassionally for rough work. 120 is where I start these days for the finishing, and then finer still for the last pass..

Retired engineer-bureaucrat in Oakland, CA. Been working with wood since the 1960's.
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post #4 of 9 Old 03-30-2020, 02:59 AM Thread Starter
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Quote:
Originally Posted by kiwi_outdoors View Post
why on earth sand off 1/8" after planing it? Just because you can?
More like because I'm new at this and didn't know any better.

My planer is a rotary attachment on my Radial arm saw, it's good at mowing stuff down but it's sure not a smooth surface when it's done. I was afraid I wouldn't be able to get rid of the circles so I erred on the side of caution. Next batch I'll plane down to 13/16 and sand 1-32nd off each side from there.

I realize I'm on a learning curve.

So if I wanted to go down to 120 or 150 should I load the drum with that or would you load the fine paper onto an orbital and do a final pass by hand?
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post #5 of 9 Old 03-30-2020, 10:07 AM
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Yes I would go with the drum sander since its available just to save time.

Any particular reason for oil based paint?

Robert
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post #6 of 9 Old 03-30-2020, 12:58 PM Thread Starter
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Durability, especially since it's trim.

When we moved into this house eight years ago the paint store employee convinced me that oil based paint wasn't available anymore and that the new acrylic latex was just as good.

He was a LIAR on both counts.

The acrylic latex chips really easily, we end up walking through the house a few times a year with a quart can and a touch up brush trying to keep things looking OK. It's just simply inferior. I think it's brittle, I wonder if oil based paint has more flex so it doesn't crack and chip as easily?

Oil based paint is still available, it's just a little harder to find. It's still used in marine applications and for painting steel and metals. It's a little more expensive at the cash register but if you add up all of the "touch up" labour it's probably less expensive over a ten year period.
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post #7 of 9 Old 03-30-2020, 08:35 PM
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Alternatives to oil if you're interested

I've used Sherwin Williams Pro-Classic Acrylic enamel on a built-in and it's proven to be very durable.

For me, at 80 grit, my old random orbit sander leaves a pretty smooth surface that I'd be happy with for most paint, but that's a random orbit sander, not a belt sander. For varnish or lacquer I'd go finer. I think it also depends on what sheen you're planning to use. Gloss shows every imperfection, but semi-gloss and satin are more forgiving, especially if you use a good primer. If you're going for flawless gloss, then you're into primer, sanding between coats and that kind of stuff to get the mirror top coat.

The purists are going to hate this, but you can get away with a little bit more imperfection on the baseboard since it's not at eye level. Also, most people aren't looking at trim up close with a magnifying glass.
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post #8 of 9 Old 03-30-2020, 09:48 PM Thread Starter
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Thanks Quickstep, I won't be going for mirror quality so I think I'll finish with the drum sander at 150 then prime and two coats of paint before install.


I guess I shouldn't consider all acrylic paint defective, I seem to be turning into a grumpy old man LOL.
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post #9 of 9 Old 03-31-2020, 05:37 PM
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Most paints require a specific 'tooth' to stick to. Think of sandpaper creating mountain tops and valleys by cutting into the surface with the sandpaper. Your surface will end up looking like a mirror image of the sandpaper. This 'tooth' oor total surface area including the mountains and valleys is called the Anchor Profile. The courser the grit, the taller the peaks and the deeper are the valleys. Each finishing product, whether a primer or actual first coating, whichever will contact the bare wood first, has a specific recommended anchor profile. Most people dont have the equipment to measure this and the manufacturer is aware of that fact. So the manufacturer, on his label on the can of the finishing product will recommend the the proper grit to be used as your final grit to sand with. It's that simple. Just read the label and you will be fine. And remember, the manufacturer wants you to succeed.

Tony B



Retired woodworker, amongst other things, Sold full time cruising boat and now full time cruising in RV. Currently in Somerville, Tx
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