Sanding questions

Discussion in 'Newbie' started by Douglas Ladendorf, Jun 20, 2016.

  1. Douglas Ladendorf

    Douglas Ladendorf

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    some questions came up for me recently around sanding.

    If you sand through the grits and see some fine lines, how do you know how far back to go in grits? One scenario is when the fine lines are clearly from power sanding. Another scenario is when they are circular along the rotation.

    When you have good cutting with little tear out, how do you know what grit to start with?

    Power sanding, how can you tell when a disk is too worn?
     
  2. Jamie Straw

    Jamie Straw

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  3. Zach LaPerriere

    Zach LaPerriere

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    Hi Douglas,

    I remember having the same question, and the only answer that ever worked for me was repetition and experience. It's taken me a while, but I can usually tell where my sanding went astray—and usually that's because I should have pulled out new paper in that grit sooner. I spend more time during sanding watching how much dust is coming out, and that's helped me to know when to change to a new piece of paper. If I'm not sure, I'll switch to a brand new piece and compare how much dust is coming out.

    An air chuck and great lighting are also helpful to avoid undersanding in a particular grit.

    Answer #2 is if you don't know which grit to go to for removing old sanding marks, try a finer grit than you think, and see if that removes the lines. If that doesn't do it, go a bit courser.

    I know this a bit of a PIA. I usually sand between grits, so if I'm unlucky enough to start at 80, next will come 100, 120, 150, 180, 240, 320, 400, 600, and 800. So in the end, I have to know what any given grit (or grit range) sanding marks looks like.

    Finally, for the softwoods I turn, 400 just isn't fine enough for my eye. It pretty much always leaves fine sanding marks, unless I'm turning a harder hardwood.

    One more thing: I've grown to be a huge fan of 0000 synthetic steel wool. It's almost like a quick buff, so I've even put the synth steel wool on at 320 or 400 to see if I've removed the other grits.

    Sanding is definitely the most frustrating, four-letter-word-inducing part of turning, but it does get easier!
     
  4. Jamie Straw

    Jamie Straw

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    Amen to that!:mad:
     
  5. robo hippy

    robo hippy

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    For where to start, that depends on how bad the tear out is. If you can barely see it, then you may get away with 120, but not higher. Grits from 80 to 120, remove wood, good for tear out and tool marks. 180 or so take off a little wood, but are more for removing scratches from coarser grits, and some rounding of edges. 320 and above are more for polishing out scratches from the other grits. I do have one sanding video clip up that needs to be updated, but not too bad. Of course, improving sharpening and turning skills goes a long way to reducing sanding time. See the long thread about Negative Rake Scrapers. I have found them to be a big help.

    robo hippy
     
  6. Douglas Ladendorf

    Douglas Ladendorf

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    Thanks all. It sounds like sanding, as with mos things, improves with experience. I'm happy to say that my tool surfaces are improving - thus the question about knowing with which grit to start. I did recently have some trouble with faint lines after full sanding and had to go back - in this case I went back to 100 or 120. The takeaways for me are to change paper more often and get better lighting. Most recently after power sanding I also did a full sanding with the grain on each grit.
     
  7. Gerald Lawrence

    Gerald Lawrence

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    You have a couple good answers.

    When I go back it depends on what I see in scratches but usually no lower than 180. I Like Robo's answer.

    Tear out is only a guess as the hardness of the wood affects that for me, usually at least down to 120 for me.

    This is a question we all have to deal with. The common answer is if there is no sawdust stream from the paper it is time to change. You can also fell the paper and feel a new piece and note how sharp the new feels, then use you judgement in feeling the used piece. When in doubt change paper.
     
  8. robo hippy

    robo hippy

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    Since I am on a sanding binge, I did try one or two 'wet' sandings where I oil it first, then sand. While it cuts the dust, I can't see the scratch patterns. I do have some that were dried with out the LDD (10 to 50% liquid dishwashing degergent, the rest water, 24 hour soak), and since the bowls are dry after the soaking, there is no sludge to fill cracks and voids, and the abrasives cut much much better. Now, only a hundred or so more to go....

    robo hippy
     
  9. Mark Hepburn

    Mark Hepburn

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    Doug,
    If I have learned one thing in my couple of years of wood turning, it was how to sand. A lot :D

    You might want to consider setting your light at a raking angle, so you can really see the lines. It's kind of disheartening at first if you're starting with hundred grit or so, but it really does help you to identify problems
     
  10. Jamie Straw

    Jamie Straw

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    Reed, I'm confused. It says you had some without the LDD, and since they are dry after the soaking....:confused:
     
  11. robo hippy

    robo hippy

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    Soak, rinse off, let dry and then sand. I am not a fan of wet sanding, it is more work, and/or time consuming. Since my bowls are warped, having the arm rests is huge in being able to hand spin the bowl with one hand, while the arm rest holds all the weight of the drill. The LDD soaked bowls when sanding yield a dust that clumps kind of like big wet snow flakes do, and we get a lot of that type of snow in the west coast. The un-LDD soaked bowls have dry powder type dust.

    Another tip I forgot about is with sanding pads. I don't like the sanding pad and the abrasive disc to be the same size. The plastic hook part of the pad will leave 80 to 120 grit scratches in the wood. You never can get the disc and pad perfectly centered on each other, and if you bring the edge of the pad into a transition, it leaves marks..... I forgot to trim the new ones down about 1/16 inch all around the pad.

    I haven't used raking light for sanding, so can't really comment about them. I have a multi spectrum type of therapy light (Blue Max) that is florescent, and very bright. Close to natural sun light so it makes things a lot easier to see. When I get to the finer grits, I hand wipe the bowl off and that highlights the 'mystery' scratches. I know I sanded them all out.....

    robo hippy
     
  12. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Reed, what are the "arm rests" that you mention? Sounds like something that I might need.

    Until a couple months ago, I did about 99.44% of my sanding by hand off the lathe, but suddenly I need to figure out how to sand without any arm motion ... or as little as possible. I also have been limited to just thinking and wishing about any kind of turning activities after apparently ripping the rotator cuff in my right shoulder all to heck. What I really want is a demented apprentice, but I hear that is unlikely since about a hundred years ago. My sanding is mainly very fine grits to level and polish spray lacquer using Micromesh.
     
  13. robo hippy

    robo hippy

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    Bill, I have my articulated sanding arm at about 3:00 in this clip. Some where in the sanding discussions lately Odie had pictures of 3 or so padded rests that just sit on the lathe for arm support for sanding. I need to get some sort of bearings for the arm to swivel on. Saw one set up where there were ring type roller bearings in between washers that some one used for an articulated arm for hollowing. I could add those to both sides of the maple chunk I have here to make the arms swivel better. Probably need to add a little more length to it, or make a new sanding hood that the banjo will fit inside of. I made the arm rests with one high and one lower because that is usually the way I hold my drill.


    View: https://www.youtube.com/watch?v=NV9lt-FNo4s


    robo hippy
     
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  14. Douglas Ladendorf

    Douglas Ladendorf

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    Reed, I have been thinking about something much like that and using the banjo to hold it. I like it and may have to make one in the future.
     
  15. Jamie Straw

    Jamie Straw

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    Post #3 in this thread.
     
  16. Jamie Straw

    Jamie Straw

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    Hmmmm, the discs I get from Vince are over-sized for the radius pads (but "same size" for the harder tapered pad, which I wouldn't use in a curve). Haven't measured how much over-sized they are, but I for sure the Velcro doesn't reach beyond the edge on the radius-edge papds. Can't say I get them perfectly center, but pretty darned close.
     
  17. Jamie Straw

    Jamie Straw

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    Reed, can I fetch some pictures and resize them for you to choose an Avatar? Hate thinking of you as a question-mark.:):p
     
  18. robo hippy

    robo hippy

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    May take you up on that some time, if I remember.... I find the question mark funny....

    I do like the orange 'medium' pads from Vince for 220 and up, but never go beyond 400, though I should try some time with the myrtle... I can get the pads and disc to line up very close, but if you go up on the edge of the pad at all, it leaves marks. Firm pad till 180 to 220, medium to 400, soft beyond that.

    robo hippy
     
  19. Bill Boehme

    Bill Boehme Administrator Staff Member

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    And ... I take my glasses off and rub my eyes when I see your fuzzy avatar. :p :D

    Maybe Reed really is a ?

    Steve gave me a spanking about my blurry avatar so now I'm going to take it out on everybody else. :D
     
  20. Zach LaPerriere

    Zach LaPerriere

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    [QUOTE="Douglas Ladendorf, post: 115135, member: 33004"
    If you sand through the grits and see some fine lines, how do you know how far back to go in grits?[/QUOTE]

    Here's another possible reason why... sanding too fast at fine grits. I'm not 100% certain this can also cause the fine lines, but a little experiment today with higher RPMs on both the lathe and powersanding seemed to produce the fine lines. Dropping the speed on both and going back to 320 and then working up made quick work of the lines.

    ...Now we just need a tutorial on how to choose an avatar! ;)
     

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