Sanding

Discussion in 'Newbie' started by Dave Fritz, May 12, 2016.

  1. Dave Fritz

    Dave Fritz

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    I hear more complaints about sanding among the turners I know than almost anything else. "I hate sanding", is a common complaint. ( I'm among them) We know good tool work is essential and will minimize sanding however in the meantime.....

    Is there a workshop or a demonstrator that specifically addresses sanding?
     
  2. hockenbery

    hockenbery AAW Advisor Staff Member

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    Bruce Hoover does an excellent demo on sanding.
    He hasn't been doing many demos lately.

    If you are going to the AAW symposium you can get some coaching from Bruce and other vendors at the trade show.
    quality hands on classes frequently include sanding

    Sanding is rarely demonstrated.
    Most turning demonstrations avoid sanding because the rooms are small and without dust collection.
    The symposiums all ask demonstrators to keep sanding to a minimum.
     
  3. robo hippy

    robo hippy

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    Vince Welch, who sells sanding supplies has a couple of sanding clips up, and I have one also, which I need to update.

    Rule 1, My 3 points before sanding: Sharp tools, cause if they aren't, then you have more sanding. Presenting the tool, how to cut cleanly without catches so there is less tear out. Moving with the tool so you get smooth even surfaces.

    Rule 2, abrasives are cutting tools that get dull, and when dull, toss them! Rubber eraser type sticks can help a bit, but they never go back to as good as new.

    Rule 3, Slow sanding speeds. Abrasives need traction to cut. If the drill and/or piece are spinning too fast, the abrasives really don't get a chance to cut as well as they do at slower speeds. Think dragsters here when they burn off their tires, lots of smoke but they are going nowhere while heating up the tires. If you hand sand and your hand is getting hot, so is the wood, and this will cause heat checks. Putting a pad on your abrasive doesn't make the heat go away, slow down and less pressure.

    Rule 4 LIGHTS You have to be able to see, and I don't think there is a turner, dead or alive, who hasn't taken a piece out in the sun light to admire it after sanding, and been horrified at sanding marks left behind because of bad lighting. I prefer the natural spectrum lights. Blue Max is a brand name, but any quilter, needle point sewer, or dentist type lighting is similar to this. Some big box stores have similar lighting, but not quite as good. Oh, if the lighting is good and you can't see the scratches, get prescription glasses. The reading glasses from the cheap store don't do the job.

    Rule 5 Dust control: Just the DC hose okay. Big gulp hood a little better. Sanding hood that encloses most of the bowl, a lot better ( I have a video clip of that one as well). You don't want it in the shop or in your lungs. I never blow off a bowl, and never understood that. One reason is that it will blow more dust out into the shop. Some say it blows out the bits of abrasive that remain from the previous grits... Well, if you are sanding the inside of a closed or hollow form, maybe. I wipe mine off by hand. Never felt any grits left behind, and if you are power sanding the disc will pull them up no problem. When I wipe them down by hand, the saw dust is pushed into any deep sanding scratches that you may have missed before stepping up and this highlights them.

    Other than that, sand till you think you have all the marks out, then hit it again lightly.

    Any particular part that really gets to you???

    robo hippy
     
  4. Dave Fritz

    Dave Fritz

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    It seems the course grits cause problems leaving sanding scratches that are almost impossible to remove.
     
  5. Tom Hamilton

    Tom Hamilton

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    I took a week-long advanced turning class with Al Lacer and I remember him saying to never use hand-held sandpaper on a bowl rotating on the lathe, because of the scratches you mention Dave. His suggestion was to always use some form of a rotating sandpaper presentation.

    I stopped using hand-held sandpaper like that then and now use a small right angle drill w/sandpaper or one of those friction driven rotating sandpaper holders and my sanding became easier and better, with a nicer result.

    Happy turning - Tom
     
  6. robo hippy

    robo hippy

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    I do some times have to start with 80 grit. When I do, next grit is 100, then 120. The scratches from 80 grit do run deep..... Most of the time when I have to start that coarse, it is with a piece of wood that just wouldn't cut pretty no matter what I did...

    robo hippy
     
  7. Dave Fritz

    Dave Fritz

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    Thanks for the feedback. Tom, it sounds like I have more than one reason to visit your shop.
     
  8. John K Jordan

    John K Jordan

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    When sanding and polish metals for microscope examination there is a thing called subsurface deformation. (In the '70s I did prep, etching, and examination of grain growth in aluminum alloys on nuclear reactor elements.) A scratch from a single coarse grit can cause damage below the bottom of the groove that is revealed far later in the process. The cure is to removed more than needed with each finer grit.

    I always suspected a similar thing happens with wood under certain conditions, big coarse grains digging a trough and deforming fibers deeper than the bottom of the groove. I imaging this might be worse with certain woods and with an excess of pressure/heat.

    I despise circular sanding scratches. My sanding:

    When sanding spindles by moving the paper against the rotating wood, I stop the lathe after every grit and sand perpendicular to the circular scratches (generally with the grain) until they are removed. My theory is if I can't take out 400 grit scratches with 400 paper, I'll never get them out with 600 grit paper. (It's worse with coarser grits.) Primary rule when sanding with the lathe spinning: spin very slowly. Other things: avoid excessive pressure and especially heat. As mentioned, good lights and good vision are necessary, not just useful. I generally sand spindles with the lathe in reverse with a mini-gulp positioned behind the work to suck up the dust.

    When sanding face work I generally don't, much. I turn as cleanly as possible being absolutely sure to remove any tearout. Then I use hand-held, generally curved, usually small cabinet scrapers to remove remaining tool marks and ripples such as in the middle of the inside bottom of the bowl that I didn't cut cleanly enough. This allows starting with a much finer grit. Instead of 80 grit, I usually start with 400 grit or 320, occasionally 220. This actually is quicker than sanding through the grits for most things. People ask me how in the world did it get the inside bottom of the bowl that smooth. That's how.

    I dislike power sanding because of the dust. When it makes sense to power sand, I've switched from the rotary sander (angle drill) to a 2" or 1" sanding pad on the tiny Grex random-orbital-sander. Rudy Lopez recommended this at the TAW symposium this year. This thing is air operated and is amazing. With the trigger pressed lightly the speed is very slow. The random orbital motion minimizes sweeping scratches with even the coarser grits where needed. This method does require a good air source.

    As mentioned, good lights and good vision is mandatory. I'm convinced that some of the horrible circular sanding scratches some people leave in the work are simply due to their vision problems. This is a shame on otherwise beautiful work.

    I prefer small, bright light sources on swing-arm or gooseneck fixtures at the lathe both for turning and for inspection. A light positioned at a glancing angle (tangent) to the surface is best since the bottom of a scratch will be in the shadow and easier to see. The "point source" lights are also, in my opinion, best for turning since they let me see and judge the compound curves as I'm forming the surface. Small turning defects such as unwanted inflection points, ripples, and curves other that what I had in my mind are far easier to see and to fix. In my opinion broad, diffuse lighting such as indirect lighting or multiple long fluorescent fixtures high on a ceiling above the lathe are the worst for seeing scratches and defects since the lighting is too even. Unfortunately, many shops are lighted this way. In this case, one or two bright movable lights (or a bright flashlight) will go for towards the perfect finish.

    During and after sanding I occasionally wipe the surface down with a fast-drying liquid. With the good lights, this is amazing at highlighting the scratches. I generally use naptha, sometimes alcohol to raise the grain (very useful when sanding). I'm sure many people have watched Jimmy Clewes use alcohol for this and ignite it with a cigarette lighter to dry it quickly. I don't do this. I don't have central fire extinguisher system installed in my shop.

    JKJ
     
    Last edited: May 12, 2016

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