Changing grits

[Mnb]

Interested to know how people decide to go up a grit when sanding?

I know the theory of not changing grits until the scratches from the previous grit are gone. How do you personally tell that you are at that point?

I'm finding that it gets easier with experience. Is that how others know?

Is there a way you use to tell or decide to change?

Do do you have a method that usually works?

[Blackout]

Hi,
I find the more I do the more I notice when I need to change. I will admit I also feel the timber to see when al the surface gets progressively smoother.
Cheers,

[Robson Valley]

On wood carvings, it's my sense of touch.
1. I'd rather finish many parts of many carvings with a textured surface. #5 sweep looks good.
2. On hardwoods, sanding fails because it shreds the surface. Cabinet scrapers are easy and cheap to make, they cut wood fiber.
3. After some sort of finish coat, I will not sand. Instead, I will use 000 coarse steel wool.
It is flat strands, it cuts like a thousand chisels without disturbing the surface finish. It cuts off raised grain.

[Kuffy]

With lower grits 80, 120, 180 I will 'lightly' draw a pencil line over the board 90° to the grain direction so that the tip of the pencil falls into the previous scratch marks and/or timber grain. Then I sand until the pencil mark is gone and then a little more. For higher grits 240, 320, 400 I just do a couple passes on every section of the board and it's done.

[Mnb]

Blackout, I haven't been using my sense of touch really. Except that after a while it starts to feel lovely. I imagine it's something you get better at with more experience too. I will try to deliberately pay attention to the feel as I go in future. To me looking works better but I have been focusing on it - where I am working now has the sunlight coming in beautifully and I can sit so I can see all the little imperfections ;) Robson Valley, When I was just starting to get into woodworking I used a scraper. I had only started getting the hang of using it when I had to move and when I was set up again I started sanding instead. No particular reason. I became determined to learn to sand well but scraping makes much more sense. Logically, cutting the fibers at a single level should be more effective than gradually making scratches smaller and smaller. I have found that wood doesn't always behave logically though. I wonder why sanding is so much more popular - or seems to be anyway. I get that there's a learning curve but there is in all woodworking. I was getting good results but with a couple of nasty scratches appearing. In another thread someone said you can file off the offending bit. Would it be an uneven bit on the bur? A little sharp bit sticking out sort of thing? There don't seem to be many explanations of how to know when to change grits. I have seen mainly simplistic ones so I was interested.

[Robson Valley]

I make my own cabinet scrapers for what little use they see. 1.25" lumber strapping steel banding, cut into 3" lengths.
They're useless in conifer and I'm not much of a woodworker in the feature-less hardwoods that we have.
I clamp a piece in a vise, chalk a mill file and try to square one edge. Don't even bother forming a burr.
The other edge gets a wrap of masking tape so I can tell them apart.

After the first coat of finish has set up good and hard, I gently buff the surface with the coarse steel wool.
The flat strands cut off all the raised grain and that's the end of that for however many more coats of finish I apply.
Lovely to work the curved surfaces of carvings. Four coats of MinWax Tung Oil Protective Finish is water-wet glossy with NO sanding at all.

[Robson Valley]

I think that using fine sandpapers on metals (sharpening wood carving tools) shows when to change grits and the larger scratches diminish.
Woods will never be like that but the principle holds well enough. Beyond 320 or 400, why bother?

So much of the common woods are now softwoods, conifers, spruce/pine/fir/cedar. Scrapers just don't work well at all.
Even Leonard Lee pointed that out in his sharpening book.
I did learn that sandpapers for wood working can be cleaned with crepe rubber to last far longer than expected.

I don't want to sand my wood workings. As I described in po.st#3, texturing a surface hides a multitude of carving sins.

[foff47]

The way I do it is when I am sanding I change directions regularly so you don't sand in the lines in the one direction, this way you can see when the grit you are using has worked, then move up to the next grit, but, always changing directions.