# Problems with lines when sanding



## Thuzmund (Dec 9, 2013)

Hi all,

So I have noticed a scary pattern: often, as I sand, I leave light swirls and lines that won't come out. In fact (and this is what scares me)-I can tell the lines are coming from my sanding, not my tools (though to be fair, I know my tools don't leave a flawless finish). I can see the lines appearing and multiplying as I sand.

This implies that even if I can get a near-perfect finish, I am destined to mar anything I turn until I get to the bottom of this. I've attached a picture of a recent bowl to demonstrate my problem:



















I had this sucker very, very smooth (for me) by "cheating" a bit with PSI Versa Chisels (Spindlemaster clones). So I was a little heartbroken that my work went for nothing.

How do others cope with or prevent this problem? Do I need new sandpaper? (I used Gator Grit with the palm of my hand 80-120-150-220, and I should note that lines form in the 120-150 range, not just the 80 range)

Any info is greatly appreciated!


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## Wildwood (Jul 22, 2012)

Besides sharpening tools more often, learning how to shear scrap or how a pull cut can help also look into getting some power sanding equipment from these vendors.
Vince has some videos here too.

http://vinceswoodnwonders.com/

http://www.woodworkingshop.com/?inMed=WOODCNT09

You-Tube will have some videos on shear scraping, using pull cut, and power sanding too!


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## bondogaposis (Dec 18, 2011)

I sand to 600 grit on turnings. You have to sand to much finer grit on turnings because you are sanding across the grain for the most part.


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## Nubsnstubs (Aug 30, 2013)

Those lines look to me like they were created by your tools. After a certain point when sanding, you think you're done with a coarse grit, you go to another finer grit. That's when you start noticing lines. They are usually not from the sanding but from you're turning technique.

My experiernce is lines appear because I've just sanded the material on both sides of the groove/cut/tearout caused from the tool and technique used to form the sides of the form.

I know this because I use an angle drill for sanding, and any lines caused by sanding are curved, rather than straight. I keep sanding through the grits until I see a straight line. I then go back a grit or two, sand and repeat going back and forth through the grits until the line disappears. ...... Persistance, smooth tool presentation and new sanding discs is the solution. ............ Jerry (in Tucson)


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## Wildwood (Jul 22, 2012)

How much you sand woodturning depends upon the wood species, and finish going to apply. Sanding your woodturning all about removing tool marks and even out the surface without leaving notable scratches.
Fact, sanding does not always remove tool marks or repair torn end grain!

See grain direction & Importance of sharp tool videos;

http://woodturning.org/education/

Stuart is not a fan of the pull cut but most American turners do use it. Even using a push cut with sharp tools may need some shear scraping.

Everyone talks about sanding sequence and agree up to a point. Think need to work toward a goal of off the tool finish. No do not always achieve my goal, lot depends upon wood species and grain direction and not going back to the grinder before making last cuts.

Before selecting a sanding sequence evaluate, wood surface first! Most film finishes only require you to san to 180, 220, or 320. Oily woods will require you to sand to higher grits. If finishing with oil or oil varnish blend will need to sand to higher grits.

Simply trying to say only sand as much as needed to give a uniform scratch pattern on the wood! Start with highest grit needed to achieve that goal and not lowest grit.

Do not skip grits, and do not go to a higher grit unit scratch pattern on surface is uniform. If have a stray scratch here and there, next higher grit might not take it out. Goal of higher grit sanding is to lessen scratches left by previous grit.

Do not use dull sand paper, sand paper wears out, so use it like toilet paper. Yes, some grades & brand sandpaper last longer than cheap stuff. Find a brand that suits you best.

Lathe speed turn speed down for sanding. Sanding at high RPM's just over heats sandpaper & burnishes wood surfaces, Do not press too hard while sanding.
I
shoot for completing 99% of my sanding and finishing with wood still mounted on the lathe. Hate to admit have still found problems once piece came off the lathe that should could easily been corrected.


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## dean2336 (Jun 8, 2010)

that is tool marks.working with spalted material you have hard and soft grains .a soft touch on finishing passes
and a continuous stream of material off the tool should mean the surface is flat.


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## a1Jim (Aug 9, 2008)

Along with the other suggestions I would spend a lot of time sanding with 60grit and then move through all of the grits with out skipping any of the grits spending a little less time with each grit up to 600 grit as Bondo sugjested.


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## TheDane (May 15, 2008)

I have recently switch to Abranet … it is not conventional sandpaper but rather is a mesh that, IMHO, does a better job. It doesn't load up like regular sandpaper and seems to stay sharp longer.

That being said, I concur with the others above … I think your sanding is simply revealing the tool marks.


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## Thuzmund (Dec 9, 2013)

These replies have been great, everybody-there's a lot to take in! But it's all good stuff, so let me see what I'm taking away from this.

So tool marks are left behind even when the surface appears "pretty darn smooth" by my beginner's standards, which makes sense. Dean, that's an interesting tip about how a continuous stream of feathery shavings indicates smoothness. I was quite pleased with myself to get a lot of wispy fluff on this project, but I do recall that the stream was often NOT continuous. That's something useful to remember next time, and of course it also makes a lot of sense, even to a beginner. 

Jerry, I will also try your suggestion of regressing periodically as I move through the grits of sandpaper. It's an easy thing to try while I begin work on getting better results with my tools (which I suspect won't come overnight). Jim, I will try 60-I was avoiding it mostly out of fear that it'd be just too coarse and rough, but I really ought to experiment with that hypothesis and see what it does on some practice turnings. For example, I have lately been experimenting with white cedar for spindlework, and even the sandpaper can cause tearout! This experience certainly contributed to my hesitation to use 60 grit with this "special" project.

I was chatting with a friend from work about this, and he suggested that cuts in wood also expose pores, which then fill with sawdust to different depths and degrees depending on how sharp the cut (which leaves pores more open than a burnishing action from duller tools) and how deep the groove that's been created. That's an interesting thought, and it might account for why these things "appear" when sanding. Perhaps the sanding isn't actually creating the lines, but merely "lighting them up" with pale dust jammed into the wood grain/pores.

Thanks again, everyone, for sharing your experience.


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## lumberjoe (Mar 30, 2012)

I hate sanding with low grits on a lathe. As others mentioned, practice scraping the surface smooth. I generally start sanding at 220. Depending on the finish, I will sand as high as 12,000 grit. I never sand below 1000 grit.


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## wormil (Nov 19, 2011)

I had that exact issue using cheap sandpaper. After switching to 3M and wiping down the wood between grits, the problem went away. The 3M cuts very aggressively, it's the most aggressive sandpaper I've used based on the amount of dust it produces. Mineral oil keeps the dust down and I feel gives you a better surface.


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## Thuzmund (Dec 9, 2013)

So Rick, you would put mineral oil on the sandpaper as you sand?


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## PRGDesigns (Jan 25, 2012)

Have you been raising the grain in between each successive grit?


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## wormil (Nov 19, 2011)

I don't always start with mineral oil but somewhere along the line I'll wipe the wood with it or dribble some on the sandpaper.


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## Thuzmund (Dec 9, 2013)

PRG, I have not been raising the grain. I see that some folks do that with a solvent-based product, and other just add water or mineral oil. Does that sound about right?


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## wormil (Nov 19, 2011)

You need water or alcohol to raise the grain. AFAIK, petroleum products will not do it. Mineral oil or wax acts as a sanding lubricant and helps fill the pores, I get a smoother surface using it especially on end grain.


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## rhford (Aug 28, 2013)

I have found that using water as I sand, combined with slowing the lathe down to maybe 200 - 250 rpms (in reverse if possible) and keeping the sandpaper moving all of the time makes a big difference. Another trick I got from Vince of www.vinceswoodnwonders.com is to paint the surface with a very thin coat of sanding sealer to raise the grain and make it stand up to the sandpaper. Sort of what shaving cream does to a beard.

Hope this helps.

Ron


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## RussellAP (Feb 21, 2012)

I think there are two ways you get this result, one is of course the tool you use to finish the turning, and the other is sanding while on the lathe. I've personally never understood why so much sanding is necessary if you have the right chisel, it should need very little sanding, but if you do sand on the lathe, I'd never just stick a piece of sand paper on something spinning at 500 RPM without expecting some lines to appear whether or not you smoothed it out well with the finishing chisel. The best answer is to get some of those pads you put on the end of your screw gun. Get the extra soft foam and use some 240G on it while the piece turns in the lathe at a low speed. It's more like a ROS that way and less likely to produce lines. 
But your time is much better spent with a sharp carbide oval tip finishing chisel. Some woods it wont work on, but most hardwoods come out much better if you don't need to sand them afterward.


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## Thuzmund (Dec 9, 2013)

Russell, thanks for your reply. This is all new to me, but it has been making sense (generally) to me as you guys walk me along. Here's another example where I treated an important detail like a simple checkbox: of course sandpaper will score wood to some degree; that's its job, right? I can see the circles forming in my mind's eye similar to layout marks drawn by pressing a pencil tip against the rotating wood. Why would it be so surprising to encounter?

My handyman side said that SP makes stuff smooth; the "circular imagination" required/developed by lathe work would have alerted me that the sandpaper shouldn't have been merely pressed on if my wish was to avoid lines.

This is, as you mentioned, assuming that the lines weren't caused by tool technique.

I have recently started working more with the skew chisels and scrapers, and trying for shearing-type cuts when using my gouges. It's definitely a primary goal of mine to unlock this latest technical mystery!

Finally, I have only just recently heard about those sanding mandrels that attach to a drill. (Now, picturing how the sanding action of the pad against the rotating wood is a great example of that "circular imagination" that I'm trying to acquire-it's kinda hard!  It would seem to me that when sanding the inside of a bowl, I should use opposing combinations of drill and lathe directions:

Lathe turning CCW (normal direction)
Drill turning CW (righty-tighty)

Lathe turning CW (opposite direction)
Drill turning CCW (lefty-loosey)

This way, the sanding action is always moving against the rotation of the wood. The other way would seem to me less aggressive, perhaps. I wonder what everyone's experience has been with that.

Thanks for all the ongoing feedback and a happy 2014 to everybody.


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## RussellAP (Feb 21, 2012)

Judging by the photo's I'd say the chisel is your main culprit here. Spalted maple is not great for uniform results. The end grain always opens up instead of cutting. What I do now is go ahead and gouge most of the material out, then use scrapers, either righties or lefties depending on your orientation, and smooth it out while you take out that last bit of material. A good sharpening before hand is a must and then a very light touch. If I saw any more lines, I'd use a round or oval carbide to smooth it out, but…and here's where you need some experience on chucking…you need to spin the bowl very fast. I usually get my lathe up to about 3k rpm. Needless to say you must be extremely careful and just barely graze the inside of the bowl and move very slowly and very uniformly. You'll get the hang of it, but please wear a face shield.


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