Stuborn sanding marks

[Bill Jobe]

Just turned this last night. Cannot get the sanding marks out. Went from 50/80/100/150/220/320.
So I went through the same process again. No help.
What am I doing wrong?

[Brice Rogers]

From the pictures, it looks like you are sanding on the lathe.

I recommend that when you finish one grit of sand paper (e.g., 50 or 80 grit) that you sand either with the grain or perpendicular to the axis of rotation. Then switch to the next higher grit. When you do this, you should sand until you cannot see the radial scratches. Then jump to the next finer grit. If you can still see the radial scratches, then you need to remove more material (axially) before changing grits.

Another thought - - your piece looks shiny. Did you apply a finish before you sanded?

[Barry McFadden]

50 seems like a very coarse grit to use on a turning.....possibly the lines are from that?...do you hand sand on the lathe or use a drill with a sanding disc?

[Dennis Ford]

I don't think you need the 50 grit again.
Sand again with 100 grit until the largest scratches are completely gone (both while turning and by hand with the grain).
Then sand with 220 until the 100 grit scratches are gone (again both with turning and with the grain).

Skipping from 100 to 220 grit allows you to tell when the coarse scratches are gone. 100 grit and 150 grit scratches are difficult to tell apart until it is too late.

If it has some finish on it already, it will gum up a lot of paper sanding now.

[John Keeton]

Looks like walnut, which is notorious for showing sanding marks. Wet sanding with oil or mineral spirits will help.

When you sand on the lathe, always keep the sandpaper moving side to side. That will minimize a scratch pattern. It also looks like you are pressing really hard - let the paper do the work using moderate pressure, particularly with coarse grits. And, finally, don't ever start with 50 grit regardless of how much you think you need to do so. It is hard enough getting 80 grit scratches sanded out. If at all possible, try to get your tool skills to where you can start sanding at 150. There may be those times it takes 80 grit, but they should be rare.

Those are deep scratches and I would go back to 80 grit and follow the advice to get rid of visible scratches at every grit. You should end up with an evenly sanded surface at every grit.

[Kyle Iwamoto]

What brand of sandpaper are you using? I found out the hard way to avoid using *-mart cheap paper. The grit controls are all over the place, and sometimes there seems to be a 50 grit rock on the 220 sandpaper, making huge scratches. After investing in "quality" paper, i see no more of this problem. Any high quality paper pays for itself IMO. Better backing means the grit stays on and cuts for longer. AND you don't get all the loose grit on your piece.
Oh +1 on NOT using 50 grit. The coarsest paper I use is 60 :eek:.....

[Dok Yager]

I agree that 60 or 80 grit is where I start. And as John said keep your sandpaper moving at all times. Also I learned a long time ago to buy "Good" quality sandpaper. I usually buy the boxes of sandpaper from Klingspor as it is Top quality and you get a lot of different grits depending on which box you choose. I too agre you start over with 80 grit and sand until smooth with each grit, always moving the paper. Here`s a link:


http://www.woodworkingshop.com/category.aspx?id=25&f1=BARGAIN+BOXES

Hope this helps.

[robert baccus]

Actually I power sand on the lathe with a 6" drill and pad--the grits are not all in a row that way. Usually 80-150-220 grits. Use high rpm,s and very low pressure is the key here. Finish up with handsanding so you can say it's hand sanded. And like the above buy the best sanding paper you can buy.

[Bill Jobe]

Well, you've all identified the mistakes I made on this piece.
Yes I sanded it on the lathe and a lot of pressure. I've gotten by with that before but this piece is particularly hard. I used a chainsaw to split a section that had 3 limbs leaving the main trunk. How I did want for this to turn out. I love the color and the cavities.
I did add a coat of Minwax Tung Oil Finish after sanding. I didn't think that finish would be a problem when I had to redo the sand.
I spent about 5 minutes blowing every bit of dust and such at about 60psi. There was a lot of crap in those holes!
Anyway, sounds like you are all in agreement that it is salvageable. That's good news for me. I was trying to replicate a vase in my daughter's living room that is about 3-3.5 feet tall. I love the shape. Was planning on removing the flute on the bottom and just have a flat that the vase curves into.
You'll notice I left it on the face plate. I knew I'd need the lathe on it again and did not want to lose dead center.

Thank you all for your comments and suggestions. I will definately be using your info. I do not want to lose this piece. And it's about as big as you can go on a HF mini lathe.

[Thom Sturgill]

One more thing to add to the list - wipe it down or blow it off after every grit. Grains can be left on the piece and trapped under the next paper causing deep scratches. Remember that the wood dust is just as hard as the wood it came from, so even grains of wood dust (rather than sandpaper grit) can cause scratching and burnishing.

[John Keeton]

Since you still can center the piece, I would consider shear scraping it to remove the deep scratches. This depends, of course, on your confidence level in doing so. That is usually my final tool use prior to sanding if the configuration of the piece will permit it. Often, one can begin sanding at 220 afterward. There are various interpretations of shear scraping, but for me it means using a side ground scraper held parallel to the surface and slanted upward with the handle low. Keep the rest as close as possible. This will produce wisps of shavings and leave a very nice surface.

[Reed Gray]

I will add some here... For best cutting with abrasives, you need slower speeds so they get better traction. For me, lathe at max 500, same with drill, with the exception here being my warped bowls which are sanded with the lathe at about 20 rpm. Too fast and they still cut, but not as well. For pressure, if your hand is getting hot, then so is the wood which can cause even dry wood to get heat checks. Most of the time, after years of turning, I start sanding at 120, though some times 80 or 100. I can start finer some times, but the time taken is greater. If I start at 80, my next step is 100, then 120. Main reason is that the scratches from 80 grit are some times harder to remove than tool marks, and 100 saves time over going up to 120. I never blow off my pieces because that just spreads more dust around the shop. I do hand wipe them off once I get up to 180 or so. This will actually push dust into the scratches from lower grits and high light them. I have never felt pieces of grit from other coarser grits on the pieces I have sanded. If I am power sanding, I can't see how a grit would stay embedded in the wood, but should come right out. If you are hand sanding, then a coarser grit piece may get stuck under the paper. Inside a closed or hollow form, some may hang around, but if you can wipe it out, you can move them. If you have to start at 50 grit, then you could use some work on tool technique. The 50 grit scratches are deeper than most tool marks and 50 grit is for serious stock removal rather than clean up. I do like to change sanding directions, so on a piece like yours, I would power sand with the spin of the lathe, then stop and hand sand long ways to make sure the previous scratches are out, then step up to the next grit. Having good lighting and good glasses are critical here as well. I am not the only one who has finished a piece that looked great, then took it out side in direct sun light for a 'better' look and then notice all the scratches I left behind....

robo hippy

[Bill Jobe]

Thanks again for more great advise.
I have a Milwaukee orbital sander that I love on flat lumber, but wouldn't you know it, the day I turned this piece it started throwing sanding discs. Did not know not to leave a disc on the pad when storing.

[Faust M. Ruggiero]

Most stubborn sanding marks are caused by not removing the prior grits scratches. In other words you must completely replace your 50 grit scratches with your 80 grit scratch pattern. If not, the 120 paper will never get left over 50 grit scratches out. The hard part is being able to differentiate between what grit scratch pattern you are looking at. Here's a trick. After your course grit with the drill, sand the next grit by hand holding the paper. Those scratches will be in a totally different direction making it easy to see if you got all the prior grit's scratches. Go back to the drill for the next grit and alternate till you are happy.
faust

[Bill Jobe]

Thanks. On my way to HD to grab a new disc. My old one started throwing sandpaper discs as soon as I turn it on.

What is the very best sand paper.
I realize the answer to that may be different for sheets and 5"discs, but I want to get both.

[William Bachtel]

Dok Yaker above answered that question, (What is the very best sand paper) and he added a link to it.

[Bill Jobe]

So he did.
My appologies, Dok Yager, and thanks for the link.

[John K Jordan]

You got some very good advice so far. I learned quickly to use good paper - I personally like Klingspor Gold in rolls but there are many others. Paper from HD/Lowes/hardware store would be my last choice.

On most pieces, especially open-grained wood like walnut, I like to apply a coat or two of sanding sealer before sanding. Either shellac or lacquer-based sealer is fine.

When I sand on the lathe I stop the lathe after every grit and sand by hand across the other scratches until they are gone. Think about it: if you can't remove, say, 220 scratches with 220 paper you will never remove them with 320!! (At least not easily)

When sanding by hand with all but the finest grits I often like to use a Magic Rub eraser as a small, flexible sanding block. But always without much pressure. When held in the hand, if the paper gets hot you are pressing too hard. Too much pressure with coarse grits can create deep sub-surface deformation almost impossible to remove, almost as bad as tear out. Too much pressure with intermediate and fine grits can cause checking in some woods from the heat. I learned that the hard way on my 3rd bowl!

I rarely power sand but mostly by hand and primarily with the lathe off. With cleaner cuts you can start with finer paper. I don't even have any coarser than 80 and don't even use that - I rarely start with coarser than 220 or 180 in worst cases. If I have to power-sand I do so with a tiny Grex random-orbital sander at a very low speed using 1" or 2" disks.

That said, instead of coarse sand paper I use small hand-held curved cabinet scrapers. These leave an amazingly good surface on bowls, platters, and forms. Much or most of my scraping is with the lathe off. After using the hand scrapers I can often START with 400 grit paper and sometimes with 600 or finer on smaller turnings.

I would absolutely use cabinet scrapers on a piece like you show, probably one with a flat edge to smooth the convex areas, with the lathe turning very slowly. They are available from woodcraft and elsewhere and are sharpened like conventional flat cabinet scrapers.

JKJ

[Doug Reesor]

I alternate between the 2 or 3 inch diameter pad sander on my drill and straight sand paper. That way as I step up to the next level of grit sandpaper you can see that all the lines of the courser fit are eliminated. Also, I use my trouble light to shine from the back of the piece as I rotate to inspect whether I have finished each grit before moving up a level. The pad sander makes the marks at a distinct angle to the regular paper and they can be easily seen.

[John K Jordan]

...Also, I use my trouble light to shine from the back of the piece as I rotate to inspect whether I have finished each grit ...

Doug, you make an excellent point about the lighting, one often not addressed. Broad, diffuse light such as from a series of long fluorescent bulbs overhead, or worse, from behind your head, makes scratches harder to see. (Worst of all is a headlamp.) Light that is too diffuse or coming from too close to the eyes also hurts truning in another way - it makes it harder to see and evaluate the compound curved surfaces we make in nearly every turning.

The best lighting to evaluate scratches is a "point" source, a light from a small, bright source, ideally at a glancing angle. This makes a shadow in the bortom of the scratch grooves and makes them much easier to see. A single bright light like your trouble light or a bright LED handheld is ideal.

I find that using several small but bright lights positioned around the work is a good compromise for general turning. I use several on swing arms or goosenecks so I can reposition them as needed. I often position one low behind the work and turn it on as needed (but I need to fix it somehow to keep the small reflector from filling up with shavings.) Besides helping me see the scratches, they let me better evaluate the surface curvature. I do have long, bright T5 fluorescents overhead for general work but switch them off while turning.

BTW, over 40 years ago while exploring caves I learned the value of using a glancing light where possible instead of a headlamp. A headlamp was invaluable when climbing or when both hands were otherwise occupied, but as the sole light source it removed shadows and wiped out my depth perception - it was hard to see small rocks and uneven ground. Glancing light from a handheld flashlight was far better. This is the same reason light from a strobe mounted on the camera makes a horrible flat photo compared to lighting from off to the sides.

JKJ

[Bill Jobe]

BTW, over 40 years ago while exploring caves I learned the value of using a glancing light where possible instead of a headlamp. A headlamp was invaluable when climbing or when both hands were otherwise occupied, but as the sole light source it removed shadows and wiped out my depth perception - it was hard to see small rocks and uneven ground. Glancing light from a handheld flashlight was far better. This is the same reason light from a strobe mounted on the camera makes a horrible flat photo compared to lighting from off to the sides.

JKJ

And red eye, or in the case of wood, glare that prevents viewing the entire piece.