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question about scratches on a bowl

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Walnut bowl. Sanded from 180 to 600 but i cant seem to get rid of these scratches.

I am a fairly new turner but I am not happy with this finish. what am i doing wrong. I thought it was nice but as soon as i applied the polishing paste they showed up.

I assume i need to drop down to a lower grit and start over sanding . The only part of the bowl this shows up on is pictured and also opposite these scratches is the same but only those 2 spots.

Appreciate the input

Mark

20191119_191931.jpg 20191119_191848.jpg
 
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You also have a bit of tear out near the rim on the first picture, as well as the scratches. Also just a bit of tool burnish marks. You moved away from the coarse grits too soon, then not enough time with each grit. Also looks like you were lucky it didn't blow apart where the growth rings are starting to separate in the first picture. I suggest you invest in some power sanding equipment, and even a random orbit sander for the outside.
 

john lucas

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Use a small.light source that you can easily move around to see the scratches. Then follow the advice the others gave you. Also helps to wipe off all the dust between grits. The sanding dust can fill the scratches and hide them.
 
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You also have a bit of tear out near the rim on the first picture, as well as the scratches. Also just a bit of tool burnish marks. You moved away from the coarse grits too soon, then not enough time with each grit. Also looks like you were lucky it didn't blow apart where the growth rings are starting to separate in the first picture. I suggest you invest in some power sanding equipment, and even a random orbit sander for the outside.

Thanks for the input . For the separation of the rings i added a gold perl epoxy i did the same with the few knots that were in the bowl . I have a power sander and a random orbit as well as an inertia sander i guess i need to wipe down in between. I was blowing it off with the compressor. Should i use any liquid as well DNA or anything?


Looks like you were in too much of a hurry to sand. Dont change grits until no sign of the previous grit can be seen. You might need to wipe the bowl down to see the scratches or change the angle of your lighting to see it.
If i buy another light the wife may shoot me 2019-11-19 21.29.10.jpg
 
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In addition to what others have said: make sure you are changing your sandpaper often, and going through proper grit progression, ie. 80, 120, 180, 240, 320, 400, etc. Powersanding is more efficient, but you can get away with handsanding. Sandpaper needs changed often—you've probably heard the saying "use it like someone else is paying for it."

The advice about a low angle, single source light is golden advice. Somehow I didn't hear that one for a long time.

Good luck!
 

odie

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I assume i need to drop down to a lower grit and start over sanding

You instinctively knew the answer! :D

I can't add much to what advice has already been given about sanding......the real trick here, is surface preparation, so that when you do sand, you've already minimized the need for it. ;)

-----odie-----
 
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Wiping off the bowl while sanding is counterproductive. You will push saw dust into the scratches and hide them and they will appear latter. Use compressed air to blow off the dust between grits. The scratches will be visible.
 

hockenbery

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I generally sand walnut to 320. Each coat of finish gets sanded with a higher grit. Too the 0000 scotch bright.

the 320 I stop the lathe and work the sanding disc with the grain lines. Any 320 scratches will be hidden by the grain.
 
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I don’t really know if it was what made a difference for me, but changing the type of sandpaper I was using changed my finish. Slower lathe speed, very light touch, and better sandpaper worked for me.
 
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If you sand by hand and your fingers get hot, you are pressing too hard or sanding too fast or a combination of both. Heat will cause some woods to crack. Allyn
 
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You instinctively knew the answer! :D

I can't add much to what advice has already been given about sanding......the real trick here, is surface preparation, so that when you do sand, you've already minimized the need for it. ;)

-----odie-----
I am working to get my gouge work good enough to start at the higher grits. I have not yet attained that level. I have been turning since January, started with a local club and am working on my technique.
 
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Well, for sure, those are coarse grit sanding marks. Being able to see is crucial to making sure you get all the scratches out from the grit before stepping up to the next grit. This means good glasses, and good light. I don't really like most LED lights because they are too white, and prefer the natural light spectrums, which are generally the florescent bulbs. I never blow off my bowls as I sand. Main reason is that it puts much more dust into the air in the shop, and to me that is a huge problem. I do wipe between each grit, and wipe by hand. In the coarser grits, you still can't see much, but in the finer grits, for me, it pushes the dust into the cracks and high lights them. If I start with 80 grit, the next grit is 100, then 120, then 150, then 180, 220, 320, and 400. The 80 grit scratches are some times more difficult to remove than tool marks, and stepping up from 80 to 120 takes about the same amount of time as 80, 100, then 120. I try to get contrasting scratch patterns. Not sure if you used the inertial sander for those scratches or not. My scratch patterns are more circular with the angle drills. With my angle drills, I use one edge of the pad for one grit, and the other edge for the next one, so I get 2 different scratch patterns. Slow speed makes for more efficient cutting. If you are going too fast, then the abrasives don't get a chance to dig in and cut, where with slower speeds, you get better traction. Maybe as high as 500 rpm for hand sanding, and as slow as my lathe will go for power sanding. Drill speed is never more than half the trigger pull. As some one on another forum said, "Never take a finished piece from the shop into the house on a sunny day. Sunlight causes scratches." I did make an articulated arm for when I sand, and that is a video I have up. This essentially holds my arm as I sand so there is no weight to support. Main thing this does, other than prevent fatigue, is to let me spin the bowl by hand. Huge advantage is making sure you get every thing sanded out before stepping up to the next grit. I spend more time with the first grit or two than I do with the rest of the finer grits. Once you get to 220 or so, you are doing more of a polishing out the scratches than you are sanding out the scratches... If that makes any sense. I did make a sanding hood, and have one up about sanding in general.

robo hippy
 
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Thanks Robo. That lathe the slowest speed I can go is 500 so I have been using that. I used the sander but I never thought to use contrasting sides of the pad for different patterns. I will also try adding the filters that I have for those LED lights to bring them to more of a daylight color and see if I like that any better.
 

Tom Gall

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From the photos the scratch pattern(s) is in a straight line and at an angle to the rotation of the lathe. This seems impossible if hand sanding or power sanding while the lathe is running. Power sanding, in my experience, will produce curved sanding scratches no matter if the the lathe is on or off, unless an extremely large disc is used.....unlikely in woodturning. If hand sanding at an angle with the lathe off seems to be the only way these scratches could possibly occur. Maybe that's just me! o_O
 
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From the photos the scratch pattern(s) is in a straight line and at an angle to the rotation of the lathe. This seems impossible if hand sanding or power sanding while the lathe is running. Power sanding, in my experience, will produce curved sanding scratches no matter if the the lathe is on or off, unless an extremely large disc is used.....unlikely in woodturning. If hand sanding at an angle with the lathe off seems to be the only way these scratches could possibly occur. Maybe that's just me! o_O

I was as perplexed as you are trying to figure out how they got there. I cannot come up with anything other than gremlins.
 
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As for removing dust between grits - I dont like blowing dust around with compressed air. I have found microfiber cloth/towels do an excellent job removing the dust from the surface. Also, I always have my dust collector running when sanding, and holding the microfiber towel in the inlet at the lathe and letting it flap around removes most of the dust. A shop vac is my backup to the towels.
 
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