Smooth Sanding

Re: Smooth Sanding

JL

>Thanks for sharing your thoughts. You say never to go over 220. Is this just for woods that are to be stained or for woods on which you are using those particular varnishes? I have on occasion gone to 320 (and even 400) for unstained woods when I want a smoother surface. I was using BLO for those projects. BTW - could this be reposted on the main?

Actually I said

bill tindall

>that I didn't go beyond 220. If you see an improvement with your choice of finish, reduce grit size, typically by two grades for each step, until you see no further imporvement. I don't think there is any harm done sanding to as fine as one wishes so long as sanding is done at each step with sharp grits and sanding stops when scratches from previous grit are removed.

I think the critical point is that wood is removed (surface smoothed) with an aggressive grit on a stiff backing. After that, the objective of sanding is only to remove the scratches from the previous grit. Because scratches are but a fraction of a thousandths of an inch deep one can not get a lumpy surface sanding just until scratches are gone. Where I have seen lumpy surfaces created is when someone sands endlessly with 220 or so trying to smooth a surface. The fine grits, or dull grits, are aggressive enought to cut the soft places but not the hard places.

Re: Smooth Sanding

Ed Mulligan, Cape Cod

>Bill -

I mostly work with mahogany, cherry and maple. Finishes are usually film-type. My sequence from rough to finish is typically power planer, then remove planer ripples with a hand plane, then remove plane marks with a scraper, then remove scraper marks with sandpaper.

For sanding if the stock is wide enough I use a ROS (PC 333 with PSA and/or Festool RO 150 with hook-and-loop) hooked up to a shop vac for dust extraction. If hand-sanding is indicated I use a cork-faced sanding block for flat surfaces.

I agree with your grit schedule and overall technique. I'd like to emphasize a couple things. First, if power sanding, dust extraction with a shop vac helps keep the sandpaper cutting evenly. It eliminates clogging. Second, replace sandpaper at regular intervals as soon as it loses its bite. You said this and I think it bears repeating. Third, count strokes if hand sanding or if power sanding methodically move the sander in a pattern so each area gets the same attention.

I can get a small table top flat enough so a reflection seen in the top has no apparent distortion. Oh, I'm sure there are a few wayward photons somewhere but it looks flat and so it is flat enough.

Ed

Re: Actually I said

Frank D. in Montreal

>Another way to get a smooth finish with oil finishes is to apply the oil with sandpaper. I use tung oil the most, because most of my projects are hard maple and I don't want yellowing that comes with age from linseed oil. I haven't seen a difference yet going over 220 before applying oil, and sanding to higher grits can burnish the surface and reduce oil penetration.

I only use higher-grit sandpaper for sanding finishes, and I thought that's what they were mostly meant for. Around here stearated papers and wet-dry are the most common papers in the very fine grits (both indicated for sanding finishes), stearated up to 600 and wet-dry up to 2000. For tung oil, after the second coat of oil I apply a coat with 320 or 400 wet dry (SIA 1952 paper backing), and use paper every 2 or 3 coats and on the last coat. This keeps the oil flat and smooth (tung gives a less-smooth finish than linseed) and if I decide to use steel wool to rub out the last coat it takes a lot less time and there are no differences in sheen that you get when the surface is rougher.

Lyn mentioned the problems that you can get when sanding too finely before applying stains, but I've read and been told by people who have more experience than me that sanding evenly and thoroughly to 180 or 220 is a good way to avoid uneven stain penetration on woods that are tough to stain. I don't see (this is a question) how a plane could prevent uneven stain penetration since it leaves cells open (it slices them, doesn't crush them); isn't it often inconsistent cell structure that makes wood blotchy? Anyways, I'm less familiar with staining problems because I don't use it much and when I do I use hide glue size.

My favorite film finish is shellac, and I use it over oil, by itself (usually rubbed down with wax, but not always) or as a base for water-poly if a piece will take a beating. Poly doesn't look that bad over shellac, really. But for these finishes I haven't noticed much difference between sanding to 150, or to 220, or planing. Again, several people who finish or make furniture for a living have given me advice not to sand higher than 180 or 220. I said I'd do some side-by-side tests on some boards so I could better see the difference between a planed surface and a sanded one with finish, and when I come back from my vacation in three weeks I will. I always use higher grits to sand the finish between coats (400, 600, 1200), and sometimes to sand the final coat (then steel wool and wax). I think sanding the finish properly is where I can make a finish look really good, clear and deep.

Otherwise for wood prep, whether I use a planer first or not (usually not) I always finish with hand planes or scrapers. I never have to go below 150, and I only hand sand. My biggest problem isn't the marks left by my planes (I don't use hand scrapers much) but the dings and dirt left during assembly, or while a piece sits around, or when I walk by it and knock it over, or hit it with a pipe clamp and have to iron it, etc. Of course I don't make a living making furniture. I use power sanders for regular carpentry jobs if I'm not inside someone's home.

Just my .02¢

Frank

great information

bill tindall

>and I feel the pain. I thought I was the only one to manage to bash something into nearly finished cabinets.

Re: Smooth Sanding

bill tindall

>Thanks for the supportive post. I recently stuck my neck out and said that I didn't see raised joints with yellow glue and dodged bullets for days over on the other side. Now I don't see lumpy sanded surfaces either. I was begining to think I needed to visit the eye (or head) doctor. Well, given some of my spelling on these posts, the eye doctor could be in order, or just finding my glases in the morning.

Not hardly Bill

Dave Anderson Chester, NH

>I don't think I've ever made a piece of furniture that didn't require me to steam out a few dings or dents from careless handling of the parts awaiting assembly. I really need to find a better and safer storage method for parts before they are assembled.

Re: Actually I said

Lyn J. Mangiameli

>A few comments:

"because most of my projects are hard maple ... I haven't seen a difference yet going over 220 before applying oil, and sanding to higher grits can burnish the surface and reduce oil penetration."

Yep, hard maple is probably the single best example of a wood (at least of the ones I've encountered) where higher grits tend to achieve a burnishing effect and reduce penetration not only of oils but of stains. I suspect it is due to the actual chemical composition of the cells more than any structural differences, but that is only speculation on my part. Still, there are times when I will take maple up to 800 or so. I never apply stain to maple, and I don't care if my oil doesn't penetrate.

"I only use higher-grit sandpaper for sanding finishes, and I thought that's what they were mostly meant for."

They are, the finest grits usually manufactured primarily for dealing with automotive finishes. The folks who are most responsible for bringing fine grits to bare wood are the woodturners. Why?, because their creations are often examined in greater detail, are handled more closely, are made of denser exotic woods, the often use oil or only wax finishes, because their work has a greater percentage of endgrain and endgrain/face grain transitions than does flat work, and because they have a high speed lathe to help them do the work

Most of my flat work uses woods that are more similar to those of a woodturner (exotics with high figure and varying grain orientation) than those who work with lots of straight grained woods like Maple and Walnut and Mahogoney. Straight grain tends to camaouflage scratch patterns, while cross grain figure, endgrain, and endgrain transitions tend to reveal it. If examined closely, even with most film finishes, you can discern the scratch pattern of using sand paper below 600, and indeed, often you can discern scratch pattern over 1000. This is more appperant in darker woods, and less so in lighter woods, and the less the film finish the more it is apparent.

"For tung oil, after the second coat of oil I apply a coat with 320 or 400 wet dry (SIA 1952 paper backing), and use paper every 2 or 3 coats and on the last coat. This keeps the oil flat and smooth (tung gives a less-smooth finish than linseed) and if I decide to use steel wool to rub out the last coat it takes a lot less time and there are no differences in sheen that you get when the surface is rougher."

For domestic hardwood surfaces that will see some wear, I concur that this is a viable approach with tung oil. For more sculptural or highly examined pieces (pens, jewelry boxes, etc). I often power buff the oil with tripoli, white diamond, and then hand buff an automotive polishing compound (Like Griots #2 or 3-M Finness-it II). The difference in clarity of figure is quite apparent.

" I don't see (this is a question) how a plane could prevent uneven stain penetration since it leaves cells open (it slices them, doesn't crush them); isn't it often inconsistent cell structure that makes wood blotchy?"

A plane (i.e, a cutting a surface with a blade) doesn't prevent uneven staining, it just doesn't cause it, at elast relative to sanding. There are lots of reasons for uneven staining and finish absorption, one of which is localized burnishing that can occur with sandpaper. As it see it, the burnishing occurs not only from the compression of the cell walls, but is effected the localized heating that can occur with power and even vigorous hand sanding.

"My favorite film finish is shellac, and I use it over oil, by itself (usually rubbed down with wax, but not always)"

Me too if I am going for a film finish

or as a base for water-poly if a piece will take a beating. Poly doesn't look that bad over shellac, really.

Ugghhh!

"But for these finishes I haven't noticed much difference between sanding to 150, or to 220, or planing. Again, several people who finish or make furniture for a living have given me advice not to sand higher than 180 or 220. I said I'd do some side-by-side tests on some boards so I could better see the difference between a planed surface and a sanded one with finish, and when I come back from my vacation in three weeks I will."

So much of this is going to depend on the wood samples you use (species, figure, density variation and endgrain content, color) and the relevance of your selection to what you usually use.

It is not just aesthetic decisions, but also the woods one uses to work with, and the uses to which they will be put, that will have the greatest bearing one what approaches seem satisfactory. What is adequate for Maple or Walnut going into a dining room table is not the same as Cocobolo or Macassar Ebony or Aboyna Burl or Wenge going into a fine wall cabinet or box. I've always be wowed by the patterns and color of highly figured wood (followed by the smell, and then the texture). These affect me more than the overall form of the piece. Some will have other or another aesthetic focus. In the end, to do as you will be doing, is the best approach to this, IMO. Comparatively experiment (and thereby expand your options) based on your own circumstances and sensibilities. That's what I have done, and again, for me, planing (and use of a skew in woodturning) reveals a level of clarity that I prize, with sanding and polishing up to very fine abrasive size, coming second.

Re: Smooth Sanding

Lyn J. Mangiameli

>Not often we disagree, but here we do.

It all comes down to differential rates of abrasion, due do varying densities and hardness within a given wood surface, that nearly all forms of sanding and buffing (materials and techniques) tends to generate, and that blades inherently avoid. Now if the abrasives on the paper were of equal size, affixed to rise about the carrier an equal amount, and the carrier were rigid and of necessary size and flatness, it wouldn't make any difference (of course then you'd virtually have a toothed blade). But this isn't the sand paper most people use.

Of course if there is little variance in density and hardness in the woods you are using, the effect will by minimal and perhaps visually unnoticable, but where the variance is great (between endgrain and face grain, or when there are large differences seasonally), the effect can be, and usually is, pronounced. Indeed, this is sometimes deliberately exploited, such as with sand blasting (the ultimate sanding without a refrence surface carrier) or sanding or buffing at right angles to the grain (I do this on Wenge bracelets).

Re: Smooth Sanding

Bill Lowrance

>I know that many people abhor exposing wood to water, but I would just remark that on small and uncomplicatedly-glued pieces, a step that can make a difference even with intermediate grits is simply "raising the grain" (mostly, raising the fluff) by wiping with a cloth dampened with water or, less effectively I think, with alcohol. Fibers pop up that have been bent over and burnished down, and the next sanding, even a light one with the same grit, chops 'em off. This can even help level an area, in that it selects-out falsely planar burnished patches.

Ooppps, more disagreements

bill tindall

>I just got up close and personal with the last few things I have made with a profiled edge (1/4 round). They are ash, walnut and cherry and sanded to 180 in one case I clearly remember and 180 or 220 in other cases. I always hand sand edges, typically with a hard rubber block and with a sanding motion at an angle to the edge. Finish is either conversion varnish, shot to give a close to wood oiled look (walnut) or shellac.

I see no scratches on end grain, and I don't think there were any there before finish either. Actually I find end grain very easy to sand smooth and bright. I usually start with a coarser grit (100) on end grind and sand until the surface is uniform bright and then it is a quick sand at the finer grits. Interestingly, this is not the case on lathe sanded pieces. I clearly see scratches even at 220 which is why I try to avoid any sanding on turned furniture parts.