sanding maple

[Joe Nasca]

hello,

I am on the last leg of my table top glue up. I will be sanding next. I am wondering the order of grit I should be sanding. thanks.

[Howard Acheson]

Sanding wood--hard or soft--beyond 220 does little more than burnish the wood making staining difficult. This is particularly true if you are using a pigment stain which sits on the surface and relies on "nooks and crannies" to impart color. Softer more porous woods can be sanded to to 220 but harder less absorbent woods may stain best if only sanded to 150. The best compromise is to aim for 180 grit.

A number of years ago a large cabinet/custom furniture shop I was involved with did series of adhesion tests with various finishes and sealers. As part of this test we explored adhesion based on sanding grit. We found about the same adhesion up to 180 - 220. Beyond 220 adhesion dropped off due to burnishing of the underlying wood particularly when non-linear machine sanders were used. This was tested on birch panels. We also found that the resulting smoothness of the first coat of finish was not materially affected by the smoothnes of the underlying wood for sandpaper grits between 150 - 220.. The smoothest surface substrate for final finishes was obtained by sanding lightly after the first coat of finish was applied and dry. Which makes the case for a thinned first coat of finish.

So our conclusion was that sanding beyond 180-220 was not necessary and could be actually detrimental.

But, most important was that there was a big appearance affect if the surface was not HAND sanded in the direction of the grain using the highest grit used on the sanding machine. A flat pad sander produced a much flatter surface than a ROS. However, both required final hand sanding with the grain for optimum appearence. If not hand sanded, swirl scratches could show. Final hand sanding using a sanding pad in the direction of the grain is a must.

To carry it one step further, sanding at 320-400 grit after the first coat and subsequent coats was the optimum. No improved appearence was noticed by between coat sanding beyond 400 for varnish. 400 was the sweet spot for thinner finishes. Between coat sanding was always done by hand whether for flattening or for adhesion.

I think you will find similar thoughts in the popular finishing books but YMMV.

Finally, the first coat of ANY finish will soak little shards of wood and cause them to raise whether the surface was sanded, planed or scraped. When the first coat of finish dries these hardened shards are what causes the surface to feel rough. Sanding with 320 paper will remove these hardened shards and subsequent coats will go on smoother. So, smoothness counts after the first coat of finish, but not much before that.

The finish left by the sizing machine determines the starting grit. Jointers, planers, belt sanders etc, should leave a finish that allows starting with 100 grit. From there, go to 120 grit and sand until the marks from the prior grit are gone, then move to 150 and finish at 180 grit.

Plywood is factory sanded to 180 grit. Therefore, it's best to not sand plywood except with 180 grit and sand by hand. Get the first coat of finish on and then sand with 320. That way you are sanding the finish, not the wood. This avoids sanding through today's very thin surface veneer.

[Dave Zellers]

Excellent info. What are your thoughts re wetting the wood then sanding again after drying as a final step before finishing?

[Mel Fulks]

I noticed in another thread today that a member posted about not sponging work to raise the "whiskers" in order to sand them lightly to remove. Long time ago around here the best private cabinet makers ,and factory finishers only sanded to
150 grit. Now every one seems to be going several grits beyond,IMO that is the difference. The dye stains work just as well on over sanded surfaces as they do on 150 grit surfaces. The pigment stains are helped ,I think ,by the "old" 150 standard. The sponging is certainly not a waste of time if it eliminates a lot more sanding.

[Joe Nasca]

GREAT info. I had completed a small maple chopping block last year. I used an orbital sander and got great results. The palm sander seemed to take forever. Since I care a lot more about this project, is it still ok to use the orbital or should I only hand sand?

[Jeff Duncan]

It depends on the condition of the top. If you have heavy stuff to remove you want to start coarser, if not finer. I start as coarse as I need to remove imperfections then move up sanding only enough to remove the last grits scratch pattern. The majority of my work goes to 150 as that's how I learned to sand coming up through the ranks. In some woods you can see the difference and it may be worth going a bit higher…..maple is not one of them IMHO….but admittedly that comes down to personal preference.

One place I'll slightly disagree with Howards' comments, (though i agree with most of them), is that I sand veneered sheet goods with 150 also. The fact that the factory sands it higher just makes my life a bit easier! If your sanding correctly you should really not having any problems sanding through. That's something I hear on these forums a lot and it just indicates to me guys don't know how to sand correctly. I routinely have to remove scuffs and scratches that require 120 and even 100 grit paper. I even steam and sand dents out pretty often, (at least one or 2 per job!), and it's pretty rare to sand through, well with the exception of defects that is. Once in a while you'll get a spot in a sheet where something got below the veneer and caused a bump, if your lucky you find it before the project gets to sanding;)

So you use the ROS all the way to the very end, then once you've got it finished take the same grit and put it on a hand block. Go ever the project a couple times being careful to use long straight lines….this is where many guys screw it up! The natural tendency of the arm/body is to create a curved motion, even when your trying to keep it straight. You have to focus on making nice straight passes back and forth as this is the scratch pattern which will be visible in the end, and a curved pattern can show right through.

As far as wetting the wood to raise the grain, that's pretty much a trick used by guys using water based finishes. If your spraying solvent based there's no point in doing it. I spray a full wet coat of catalyzed lacquer then let it dry for at least a couple hours. Flat panels then get hit with 400 grit on the ROS and a finish pass by hand, (though I agree the 320 will work as well). Anything else gets hand sanded with 400 and then a second coat of finish. Makes for a great, durable finish….for cabinetry, at least IMHO:D For a table top you'll probably want something even a bit more durable?

good luck,
JeffD

[Brian W Smith]

Probably shouldn't respond....oh well?

"Burnishing" is a problem,irrespective of the grit........the paper(grit),gets dull and you're going backwards.

Sanding,possibly better stated as "grinding",is a cutting action,moreso than a "polishing" process..And,just like a blade,when the process stops being "cut" and turns into a burn of sorts....problems arise.Thes problems may or may not show up in the machining dept(depends on the skill/experience of the operator),but it will show up in the finishing rm.Heck,books have been written on the subject.....do yourself a favor and do a little reading on "sanding".Widebelts would be one area to start your research.Look at the issue from a wider viewpoint though.....meaning,what works for/against widebelt finishing....and how that correlates to doing it by hand for instance.The process is very dynamic in this sense.

[Mike Heidrick]

Make sure you have good lighting when sanding maple.

Consider your finish when planning the sanding methods and grits.

[Joe Nasca]

The planks that I joined have been sanded at the factory. They are relatively flat and smooth. The sanding will basically be smoothing the joints.

I am not overly positive which stain and finish I will be selecting. This project is a coffee table. How does sanding relate to stain/finish? Can someone recommend me a good stain that will have a better shot of adhering/absorbing into the maple. I know maple does not take kindly to stain, but I assume there are stains that are significantly better than others.

[Mel Fulks]

I don't agree with the anti sponging comment. As obsessively stingy as some of the old time employers could be about
sandpaper they still insisted that a NEW piece of 150 be used for the post water de-whiskering. It's easy for a ding to disappear with some sanding and then reappear at application of water stain. They had very strict rules about who did what ,the finishers sanded NOTHING other than finishes. No matter how slight a flaw was the cabinetmaker had to move the piece back into the shop,fix the problem,and then return furniture to finisher. Strict but efficient,much better than some new
things I've seen ,like letting some "ace" slap together product then send it to someone else for sanding.

[lowell holmes]

I do more scraping on maple than sanding. There is a video on the Fine Woodworking site that shows how to sharpen a cabinet scraper. It works!

If I do sand, I agree with Howard's assessment. I never sand beyond 220.

[Chris Padilla]

If you have the opportunity and the time and the material, try this:

Sand pieces of comparable maple to 120, 150, 180 and 220 grit, respectively. Now stain/finish them all the same way. Do you see any differences?

I like to use oil/varnish blends and mixes as my finish of choice and I find sanding maple to 150 to work for me.