General Sanding Questions

[Erich James]

When sanding wood, before progressing to the next level grit, do all of the scratches need to be removed, or just reduced? If you don't get all of the scratches out, will the next higher level grit get them out?

I'm working on what I have been told is douglas fir, and am progressing from 50 grit from a belt sander to 60 grit from a vibrating handheld sander, and I don't know if I can get all the scratches out, or how long it will take.

Also, can you switch between a belt sander and a vibrating or orbital sander as you move through the sanding process? Eg. 50 grit belt sanding, 60 grit vibrating handheld sander, 80 grit belt sander etc.

Thanks,

Erich

[Jay Allen]

50 grit belt sanding scratches in a soft wood like fir might be pretty tough to get out especially if they are across the grain. I think I would step down to a finer grit on the belt sander first and be sure that the cross grain stuff is totally gone. Then go to the orbital sander with the same grit before going finer.
How fine do you need to be? What kind of finish is going on this?

[Erich James]

Then go to the orbital sander with the same grit before going finer.
How fine do you need to be? What kind of finish is going on this?

You mean go a step down to a finer grit, meaning 60 or 80? And sand until they are gone? And going to the orbital with the same grit meaning that 60 or 80?

I'm not sure what I'm going to finish it with yet. I'd like to keep the wood light and the grain dark, but that sounds like a lot more work.

[Jay Allen]

Yes, you always need to eliminate the previous grit's marks. Of course this is all relative to your final goal. Stains, especially darker colors (or ones with higher percentage of pigment) show scratches more than other finishes. But if you sand too fine, the stain will not "take" as dark as you expect, so it's kind of a trade-off.
Staining soft wood is usually a bit of a challenge anyway. It has a tendancy to be blotchy and mottled because of the density of the fibers.
I am not particularly a fan of softwoods though, so my experience is pretty limited.

[Charles Lent]

If I use 60 or 80 grit, my next step would be 100 or 120 grit, then 150-180. I rarely sand finer then 180 grit, as stains won't penetrate well when a board is sanded to a finer grit level. During the finishing process I use progressively finer grits between coats to arrive at the desired final finish, sometimes going as fine as 1000 grit. It all depends on what the desired end result is.

Charley

[David Helm]

For your application I wouldn't go any finer than 120 or 150, and I wouldn't try to stain it. Daly's makes a product called Benite that seals grain and helps keep it from blotching, but trying to stain the softwood is a fools errand. As I mentioned in your other post, from exposure to air fir tends to darken with a hint of redness. My entire house is trimmed out in CVG Douglas Fir (this is sanded finer than the beams for obvious reasons). When going with this wood you will find that it is quite expensive as the fine grain stuff only comes from "old growth" ($7 to $8 per board foot here in the Northwest where it comes from).

[Erich James]

If I use 60 or 80 grit, my next step would be 100 or 120 grit, then 150-180. I rarely sand finer then 180 grit, as stains won't penetrate well when a board is sanded to a finer grit level. During the finishing process I use progressively finer grits between coats to arrive at the desired final finish, sometimes going as fine as 1000 grit. It all depends on what the desired end result is.

Charley

So, if you last used 60 grit, the next grit you would use would be 100
and, it 80 grit, the next grit you would use would be 120?

[Erich James]

For your application I wouldn't go any finer than 120 or 150, and I wouldn't try to stain it. Daly's makes a product called Benite that seals grain and helps keep it from blotching, but trying to stain the softwood is a fools errand. As I mentioned in your other post, from exposure to air fir tends to darken with a hint of redness. My entire house is trimmed out in CVG Douglas Fir (this is sanded finer than the beams for obvious reasons). When going with this wood you will find that it is quite expensive as the fine grain stuff only comes from "old growth" ($7 to $8 per board foot here in the Northwest where it comes from).

Thanks, David. I've also heard that there are water based products use can use to seal soft wood that will give the wood a color blended look. Then you can stain the wood, and it will look more color-uniform. Have you had any experience with these products, or have you seen any work done with them? The product you mentioned above might be what I am talking about.

[Charles Lent]

Erich,

I sand to remove the scratches that are bigger than the ones that are being made by the paper that I'm presently using. When I pick the next paper grit size I try to pick one that is 1/3 to one half the grade number larger. In other words, if using 60 the next grade would be 100 or 120. If using 120 the next grade would be 180 or so. The exact grade step isn't critical. With each step you should strive to remove the scratches that are bigger than the ones left by the previous grade. If you choose a grade that is significantly finer than the one that you are using it will just take a little longer to sand away the previous grade's scratches. If you choose a smaller step in grade the sanding will go a little quicker for that step, but too many small steps in grade isn't really practical because it becomes very difficult to see a difference. A little practice will tell you what works best.

Charley

[Prashun Patel]

I am still perfecting my sanding technique.

Here's what I know:

Be careful with grits coarser than 100. They can quickly make divots in yr project that'll show up during finishing.

It's been hard for me to tell which scratches are made by the 50/60 grit and which were made by the milling/cutting process; so it's hard to know when to stop.

What I do lately is work quickly through the grits up to about 180 or 220 - not paying attn to removing scratches. Then I wipe it thoroughly with mineral spirits and see where I need to work. This eliminates about 90% of the oversanding that I'd otherwise do, and makes me focus on the problem areas. I find almost all the time that I can start again at 100g - especially on soft wood.

[Erich James]

I am still perfecting my sanding technique.

Here's what I know:

Be careful with grits coarser than 100. They can quickly make divots in yr project that'll show up during finishing.

It's been hard for me to tell which scratches are made by the 50/60 grit and which were made by the milling/cutting process; so it's hard to know when to stop.

What I do lately is work quickly through the grits up to about 180 or 220 - not paying attn to removing scratches. Then I wipe it thoroughly with mineral spirits and see where I need to work. This eliminates about 90% of the oversanding that I'd otherwise do, and makes me focus on the problem areas. I find almost all the time that I can start again at 100g - especially on soft wood.

I'll try this, as well as the techniques others have posted on, and report back.

Thanks to all,

[Steve Jenkins]

If it is solid stock that I'm sanding I will use my belt sander up through 150 grit then hit it with an orbital and 180. I seldom if ever start coarser than 80 more likely 100 or 120. I run the belt sander at a slight angle like 11:00-5:00 then when I change grits I go at a different angle 1:00-7:00. That way you can easily see when you have removed all the scratches from the previous grit.the last grit with the belt sander is done straight with the grain.
It's usually suggested that you skip no more than one grit size. any more and you spend a lot more time sanding than necessary.