2 part sanding question

[David Warkentin]

I have a couple of questons for my friends here. When I sand a bowl and put finish on it, I can see scratches from sanding. I am using a sanding kit from Vinces. I believe it goes from 80 to 400 grit in six discs. I use a cordless drill to sand. What am I doing wrong?


Next question. When I laminate walnut and maple together and sand them I am getting walnut dust staining the maple. And it won't come off. Any advice for this problem? Thanks for all your answers (I hope):D.

[Roger Chandler]

Next question. When I laminate walnut and maple together and sand them I am getting walnut dust staining the maple. And it won't come off. Any advice for this problem? Thanks for all your answers (I hope):D.

David,

You might have to do most of the sanding on the different woods first, then join them together............it is a pain, and requires extra time, but it may be what will keep the pieces from staining one another. Just a thought.........not sure if it is the correct answer.

[Lee Koepke]

My opinion on the first question is, you arent getting all the previous scratches out. One method I read about and use is after machine sanding, hand sand in one direction (ie like for pens, the length of the barrel ) that orients the 'scratches' in the proper direction.

You can wipe mineral spirits or DNA after each progressive grit to see if there are residual scratches left. They should be getting harder to see each time. this also cleans off previous dust / sanding grit that can stay behind and scratch. Example, you may leave some 150 grit behind, then your 220 pad will be grinding the 150 instead of 220.

The second one ???? Not sure. I generally dont have that problem when I use maple and walnut together for my cutting boards, but I also sand in the direction of the grain, and usually sand by hand. the swirling motion may have something to do with that (see the answer to question 1)

[Clint Baxter]

In answer to the first, when using one of the finer papers/disc, you're evidently not getting all the scratches removed from a previous coarser grit. Oftentimes, you may no longer be able to see those scratches but they may still be there. Some wood types are, needless to say, more likely than others to have this show up on. Scratches are much more likely to show up crass grain as well. Some will stop the lathe and sand with the grain as the final step before moving on to a finer grit. Reversing the direction of the lathe seems to help in removing all scratches as well if you have that capability. You might be able to expose any remaining scratches with a quick wipe of mineral spirits before going to a finer grit as well.

As to the second, is it possible that they aren't getting sanding enough? If your maple has small scratches from your sanding, the walnut dust would stick in them and cause the "staining". I've never seemed to have my maple colored by adjoining walnut, but that doesn't mean your wood isn't doing that. JMHO.

I'll be monitoring this myself to see if there are any other solutions/suggestions from the experts here.

Clint

[David Warkentin]

On the second question; I can't sand before hand. I laminated approximately 5/16 x 1 1/2 inch strips together. Then I cut them on an angle across the strips, maybe 20 degrees, not sure, then turned it for a handle on one of those pigtail turner things from Craft Supplies.

[David Warkentin]

When I do segmented bowls I don't seem to have nearly the problem with staining. Maybe the stain is just showing up on end grain. Maybe more sanding needed. Maybe I just answered my own question.:D

[David DeCristoforo]

This is an issue that plagues all woodworkers, not just turners. Sanding on the lathe presents it's own unique set of problems. The primary "rule" of sanding is that you sand with the grain. But most sanding on the lathe is done with the piece rotating which means that in many cases you are sanding across the grain. Cross grain sanding scratches are much more difficult to remove. Additionally, when you use a disk type power sander, the sanding is in a circular direction from the rotating disk, not "linear" as it would be if you were hand sanding a board. So even if your grain orientation is such that a stationary piece of sandpaper would be cutting with the grain, you are still getting a cross grain scratch pattern.

It is often difficult to see sanding scratches until you apply a finish coat. You need a good strong light positioned so that the light reflects from the surface toward your eye. This will usually reveal any scratches remaining from previous grits. It is important to remove all fine sanding dust from the surface before inspecting it. Fine dust can obscure remaining scratches. You can also wet the surface with a non grain raising liquid like alcohol or lacquer thinner. This will immediately reveal scratches that might otherwise escape detection. These liquids will evaporate quickly and will not alter the wood color.

Finally, I always finish sanding by stopping the lathe and hand sanding with the grain. I do this with each successive grit. It only takes a minute or two and will quickly show any cross grain scratches you may have missed. Do not make the mistake of thinking that sanding with the next finer grit will remove stray scratches from previous coarser grits! This will only lead to your having to strip your finish coats and resand. Lots of needless extra work.

As to your second question, I had to deal with this problem extensively when I used to make a lot of chessboards. You may find that the dust from the darker wood discoloring the lighter wood. But maple is pretty dense and there are no open pores to hold actual dust. So you may be "burning" the walnut color into the maple through the heat generated by power sanding, something that becomes more of an issue with the finer grits. You will have to do some hand sanding on the lighter woods to remove it. A chessboard is flat so I always used a card scraper for most of the smoothing to avoid contaminating the light woods. I have never done any segmented turning but there are a lot of guys who do and they may have some specific tips on this.

[Bernie Weishapl]

David you have gotten some good advice. I always blow the dust off after using each grit. After the 150 grit I use mineral spirits to check to see where I am at and also after 320 grit. I do reverse my lathe on every other grit and stop the lathe to sand with the grain. I have never had walnut bleed on any light wood that I have laminated together. I had what looked like bleed over in some oak/walnut that was just dust in the pores which blew out easily.

[David Warkentin]

Wow! All this great info! Thanks.

[David DeCristoforo]

One other thing to keep in mind. If you do use alcohol, lacquer thinner or mineral sprits, these can pull color form some woods and "bleed" them into the adjacent lighter woods. Padouk and cocobolo are especially prone. Test on sacrificial wood first! Many use water to dampen the wood both to reveal any errant scratches and to purposely raise the grain. Subsequent sanding will cut the fibers raised by wetting, resulting in a smoother surface, albeit at the cost of additional sanding.

[Fred Perreault]

David, I also use air to blow the sanding dust off of mixed wooden ware. I laminate contrasting colors often, and learned early that the coarser, more open grained wood held dust that could be sealed into the grain if not removed. And have clean air, no oil or water in the tank and lines.

[Reed Gray]

As said by others, the sanding scratches are probably from not getting all the others out before you move to a finer grit. The one bad thing about using 80 grit is those scratches are as hard to get out as tool marks some times. When I first went to power sanding, it was a real problem for me as well. A couple of things can help out a lot.

First, you need excellent lighting. One of the multi spectrum lights that most imitates natural sun light in brightness and spectrum makes a big difference. Ott, and Blue Max (used to advertise in Woodturning Design) are two brands, and if you have some one around you who does hand quilting or fine needle work, they will most likely have this type of light. If you are sanding and take the bowl out in the sun to see, things will show up that weren't there before. This is also time to consider good glasses if you vision isn't quite what it used to be.

Another thing is to vary your scratch pattern. I used to hand sand just a bit to see if there were any remaining scratches. The straight lines from hand sanding would contrast with the circular ones from power sanding. You can also get a different power sanding mark depending on how you hold your drill.

I don't want to put any mineral spirits on my bowls. While I don't blow them out, I do use my hand to wipe the surfaces of the bowl. The dust from the higher grit will actually work down into coarser grit scratches and high light them. More so as you get to finer grits.

I frequently will sand with the lathe off, and slowly rotate the bowl by hand while power sanding. This also allows you to see the scratch pattern change. I do some times on all of the grits.

Sand till you think you have all the marks out, then hit it one more time.

robo hippy

[Leo Van Der Loo]

I have a couple of questons for my friends here. When I sand a bowl and put finish on it, I can see scratches from sanding. I am using a sanding kit from Vinces. I believe it goes from 80 to 400 grit in six discs. I use a cordless drill to sand. What am I doing wrong?


Next question. When I laminate walnut and maple together and sand them I am getting walnut dust staining the maple. And it won't come off. Any advice for this problem? Thanks for all your answers (I hope):D.

David the first paper you choose is the most important one, it should take out all the tool-marks and rough spots, but just because the sanding kit goes from 80 grid and up, that doesn't mean you should start with 80 grit, especially with softer wood, the wood can be torn by this coarse grit, and the scratches from coarse grit can/will go deep, and then you will have to do a lot of sanding to get those out again.
Also using two woods that are very different in hardness will make it harder to get both all equally sanded, good light as has been mentioned already is needed and hardly ever good enough, concave curves are very hard to get to show any scratches that are left, taking the piece off of the lathe to get into better light and position to see, is what I have to do quite often, (my eyesight isn't getting any better:rolleyes:) even then having to go back and re-sand sometimes is not uncommon, a finish will make scratches stand out, so using a wetting to show them is a good idea.

Cross contamination is a problem with some woods, sealing open grain first can help prevent this from happening, color bleeding also can be reduced by sealing first, something we all seem to learn the hard way :)

[Jim Silva]

Hi David,
As for the first as others have commented, it's not how many grits you use but how effective you are when using them. Too coarse a grit on soft wood makes deep scratches that requires far more sanding to remove with subsequent grits. Not coarse enough leaves tool marks, etc etc. Sanding pressure can cause issues also. Try not to apply too much. Let the grit do the work and check between grits with mineral spirits or alcohol to see what you have left.

As for the bleeding, I'd suggest as Leo did to use a sanding sealer before you begin. Don't be afraid to thin it further than it comes out of the can either. That may help.

Jim

[John Keeton]

I usually start with 150, and spend 75% or more of sanding time with that grit. From there upward, it takes very little to remove the previous marks. But, you cannot skip grits. Also, I have gotten away from power sanding whenever possible. I have much better success getting a good finish by hand sanding. But, I don't do many bowls, and those I do usually power sand.

I do a lot of walnut and maple together, both in flatwork (in a prior life!:D) and in turnings, and have never experienced the problem you describe - no help there.

[neil mackay]

if your having a problem with scratches etc. Then perhaps its back to the old maxim, "down through the grits each and every one, missing none"
I dont always do this, but with some timbers you have no choice and it can be a slow process, good luck

[Thom Sturgill]

Lots of good advice, so I'll throw in my $.02

Make sure that you are not loading up the sandpaper. Power sanding can cause more heat and cause the paper (or disk) to load up with dust which burns and can cause deeper scratches and dis-coloration.

[David Warkentin]

Thanks very much for the answers. Went back out to the shop and got that walnut/ maple handle basically done. Looks like maybe the walnut dust was getting into the endgrain on the maple. Sanded some more and it will be fine. Haven't tried another bowl yet to check those sanding marks.

[John Beaver]

Glad to hear you got it all worked out.

For the future with contamination issues, first thing I'd try is a strong air compressor to blow the Walnut dust out of the Maple. If this doesn't work, then the next step is to apply sanding sealer before sanding. For some challenging combinations I have used sanding sealer, followed by very light sheer scraping a couple of times before sanding.