Can you go too far with sanding?
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17 January 2015 at 10:56 am #123598
Hi guys,
Just glued up my first dovetail box. After planing the edges as Paul shows, the box sat perfectly flat on the base. No rocking, no gaps. Got lucky!
Then I thought I’d sand the sides and the base and started at 80 grit working my way up to 1200. I used a sanding block. When I finished at 1200 I wet the box and base down with a spray bottle of warm water to raise any grain and then waited until it was dry. I’d read this somewhere and it seemed like a good idea at the time.
The box sides were fine but the thin base cupped badly. Fortunately, I left it in the sun (very hot Aussie summer here) with the convex side up and it flattened out again.
However, when I placed the box on the base, I had small gaps on the edges where the box and base meet. Not gaps from anything warping it seems as no light shows through and the box doesn’t Rock on the base. It’s seems like the edges of the box have been rounded just enough that they don’t quite sit perfectly flat on the base. I’m wondering if even though I used a sanding block, I might have rounded over the edges?
Anyway, I’ve glued it up and I’ll put some shellac on it tomorrow. Strangely, the box feels very smooth after sanding to 1200 but it wasn’t that bad to begin with after planing. What grit does everyone here start and stop with?Andrew
17 January 2015 at 4:09 pm #123616i try to get my surface smooth off the plane the only sanding you have to do then is with 220/240 paper to roughen the suface to take a finish if the grain is going to rise it will rise after the first coat of finish, i use fine denibbing pads to knock this down .
17 January 2015 at 9:26 pm #123618Andrew, as Eddy says, Paul advocates just light sanding with approx 250 grit after planing. If your surface is reasonably smooth after planing (and we should all strive for a pristine smooth planed surface), then all you need is light sanding with 250 grit. It seems to me that starting with 80 grit is far too coarse and ending up with 1200 is far too fine. You should only need 80 grit if there are deep scratches and you need to remove a LOT of material. Having said all that, I don’t think I’ve heard of anyone sanding more than 400 to 600 grit – back in the power tool woodworking days I would start with about 100 grit and stop at 220 grit.
I get the smoothest surface off the plane, and I cringe a bit at having to mess that up by sanding (roughening) to accept a finish. I go with 250 or so, and yes, you can sand an edge even though you are using block, because the paper will roll over if not completly taught. This article may be of help. http://www.jamarco.com/91b_Technical/sandpaper/Making%20Sense%20of%20Sandpaper%20-%20Page%202%20-%20Fine%20Woodworking.htm/ if the link wont work, this is the section of interest:
“Sand bare wood to 180- or 220-grit–For sanding bare wood, 180-grit will generally give you a surface that looks and feels perfectly smooth and is ready for a finish of some kind. Sanding the surface with a finer grit is only necessary if you’re going to use a water-based finish. These finishes will pick up and telegraph the smallest scratches. Sanding the wood to 220-grit or finer will prepare the surface better. However, it’s not always wise to sand to a finer grit. You will waste your time if you can’t tell the difference, and you may create problems in finishing. Maple sanded to 400-grit will not take a pigmented stain, for example. Pigments work by lodging themselves into nooks and crannies on the surface; without them, they will have no place to stick.”29 January 2015 at 8:03 am #124057I think somewhere we are introducing one of those unknown sources here that might be better addressed now. There is no need to sand anything more than 250-grit, sometimes 350 max. Generally there should be no need to start as coarse as 80-grit either, unless the wood absolutely won’t plane because the grain is just too wild. If planed using a well sharpened plane, the surface (sometimes) is more likely to need roughening a little, to give the surface tooth for the finish. Wetting the surfaces of boards isn’t a good idea and especially unconstrained materials and thin flat panels especially. Wet a board with water and it has no choice but to curl and crawl all over the place. There is no doubt that we can indeed go too far with everything, the questions is, how did we get to there?
29 January 2015 at 10:10 am #124062Thanks Paul,
I was led astray by reading a publication widely heralded down here in Oz called “A Polisher’s Handbook.” It’s put out by the guys that make U-Beaut shellac and other products. I won’t slight the book, as its a much revered publication in these parts. In my beginning enthusiasm I must have misinterpreted the bit that said if you want a good finish, sand to 1200.
There was also a part that said after sanding wet down the surface with hot water to raise the grain.
Oh well, live and learn. Next time I’ll just go to 250 grit and forgo the hot water.
My “chisel tray” box looks good nonetheless and I learned so much working through various problems along the way.
I’d like to make a few more for my better half and my step daughter. Both have requested jewellery boxes with the fitted lid but that also want the divider like the dovetail caddy. It should give me some good practice before I tackle the joiners toolbox.
Thanks again Paul and also everyone else around here for providing so much help and encouragement and a welcoming place to learn and share.
Andrew -
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