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Sanding inside hollow forms

Discussion in 'Woodturning Discussion Forum' started by Brandon Sloan, Aug 15, 2019.

  1. Brandon Sloan

    Brandon Sloan

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    I can get a pretty decent finish cut on the inside of my hollow forms but I’m pretty new to this and my idea of decent might be skewed.

    I’ve never seen any other hollow forms in person and am curious about how far people go to get a perfect interior surface. Also any tips would be welcome.

    My second hollow form, it’s Alaskan birch. I was able to get this one pretty thin because the light shines through. Any advice or feedback is greatly appreciated. I haven’t found any other wood turners in my area. I’m sure they exist. Anyone in Fairbanks area??

    (Sorry, I just read the sticky that says “read this before posting” hopefully one of the nice moderators will move it to where it belongs)

    EA89330C-AEBD-4142-9FDA-8CF45E5BCCD2.jpeg 713C18BA-FFE8-4317-85C7-1177958718D8.jpeg C7F68BBD-0A60-4ABE-AA95-4857E3BA33A9.jpeg
     
  2. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Thread has been moved to the Woodturning Discussion Forum. Sanding the interior varies all over the map, but my take is that most people don't worry much about it unless they feel there is a need to have a smooth interior. For deep hollowforms I have a broom handle with a ball of 60 grit Velcro backed sanding strips on the end. For normal size hollowforms I have a ⅜" dowel with a smaller ball of the same 60 grit sanding strips. I don't ever poke my fingers inside with the lathe running. I learned that lesson the hard way when I was a beginner. Just take my word ... it's a really dumb thing to do.
     
  3. Brandon Sloan

    Brandon Sloan

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    Thank you, do you add any finish to the inside?
     
  4. Bill Boehme

    Bill Boehme Administrator Staff Member

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    There are five AAW members in Victoria and three more if you include Halletsville, Cuero, and Port Lavaca. If you are an AAW member you can use the AAW Member Directory to find other members.

    Sometimes (most times probably) I finish the interior. Flat black gesso makes it impossible to peek inside. You need to be really careful about trying to spray a finish inside because it will come straight out at you so be well out of the line of fire and wear clothing that you don't mind ruining. I also used Krylon stone finish once where I wanted to create a thrown pottery look.
     
  5. Brandon Sloan

    Brandon Sloan

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    I’ve met and turned with most of the guys in Victoria and Dr. Hill in Cuero, great group of guys and I’ll be moving back to that area soon. Right now I’m in Fairbanks, Alaska. Not much up here.
     
  6. Bill Boehme

    Bill Boehme Administrator Staff Member

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    There are 12 AAW members in the Fairbanks and North Pole area. There are probably several others who aren't AAW members.
     
  7. Brandon Sloan

    Brandon Sloan

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    Thanks Bill, I’ll have to track these guys and gals down.
     
  8. charlie knighton

    charlie knighton

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    Is much smoke from wild fires in your area????
     
  9. Brandon Sloan

    Brandon Sloan

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    The smoke was pretty bad for about three weeks. Air conditioning isn’t that big up here if you have the option of opening your windows. The smoke was so bad one day that I couldn’t see the trees in the yard.
     
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  10. hockenbery

    hockenbery AAW Advisor Staff Member

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    The three most important things about a hollow form are
    Shape, shape, and shape
    Fourth is outside surface
    Last is wall thickness( has to be even and less than a 1/4” to prevent cracking)

    I rarely sand the inside of hollow forms. I do use a teardrop scraper to smooth the surface. I don’t want any ridges.

    I treat the indies to go with my vision of the outside.
    If a piece has lots of voids I often bleach the Inside.
    Most pieces I finish with Waterlox - the inside gets 1 coat of Watco or Waterlox.
    If the outside is painted I will usually paint the inside


    Inside Waterlox - 12”D Osage orange- this one I sanded inside it is almost a bowl.
    6DB80DE8-BDBE-48D2-90E1-9A7BCCFA1228.jpeg

    Inside bleached 15”D maple
    03B92D05-57A7-48B4-B0E5-F35929AD68EA.jpeg

    Inside painted 8”D Campher
    BD2DE373-1EFD-4F1F-B35F-86A6F59E21BA.jpeg

    Inside nothing 7D cherry
    D93A898B-C31A-4C8D-A9D3-C865A54733A1.jpeg
     
    charlie knighton likes this.
  11. Brandon Sloan

    Brandon Sloan

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    Wow! Those are really nice, thanks for sharing. I woke up this morning and found cracks in my hollow form. The shoulders were a little to thick.

    Do you use more than one bent tool? I bought two of the Trent Bosch cutters. One straight and one bent. He has an extreme bent tool, would that be the tool to cut the hard to reach area in my image?


    0972FD22-06EA-44E3-B1D6-9AF4D2C599DC.jpeg
     
  12. charlie knighton

    charlie knighton

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    The elbow tool for hollowing can do 90° about 3" & I guess you could fabrication a cutter for more length....the original elbo's were square stock but now round....needed about 1" entry and careful....hollowing @ 90° has been said to have more wear on bearings....i cannot really say but have had mine changed mainly because of multi-axis work ....so 90° and multi-axis something caused wear
     
    Last edited: Aug 15, 2019
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  13. hockenbery

    hockenbery AAW Advisor Staff Member

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    Thanks!
    In a room kept at 50% relative humidity, I dry my hollow forms in a cardboard box for a few days. Flaps closed for a day, one flap open for a day, All flaps open for a day, sit of a shelf for a day the sand an begin finishing.
    This keeps the form from drying too quickly.

    The extreme bend will give you a little more reach into the shoulder area. About an inch maybe a little more depending in the opening diameter and the shape of the top.

    My forms are mostly rounded on the top. This has two benefits for me.
    First I like the look and sense of volume the rounded tops give
    And second much easier to hollow the rounded top than the flat or recurved tops.

    I also have a tool made by my friend CA Savoy who is no longer with us. I use this one close the opening where he regular hook tool cannot go.

    Al


    E6E05D21-F11E-4510-A98D-A427E7032B73.jpeg


    909266A6-A500-4BF6-AC96-11074A9BC28B.jpeg
     
    Last edited by a moderator: Aug 15, 2019
  14. Brandon Sloan

    Brandon Sloan

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    Thanks for the drying tip, I will try it on my next hollow form. I have a lady who is going to let me have a bunch of birch that has been sitting for around 2 years. She just wants a bowl or hollow form.

    It’s funny you mention your Savoy tool, I just came across a similar tool and thought it was a good idea. It was included in the Keith Clark hollowing system.

    Do you have any experience with those teardrop scrapers? I was thinking about ordering one with the extreme bent tool.
     
  15. Brandon Sloan

    Brandon Sloan

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    Off topic, but here’s a Birch bowl I finished this morning. 2AAC321C-C24E-484D-B08F-E53121801A15.jpeg
     
  16. Brandon Sloan

    Brandon Sloan

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    You already answered my last question. Is the teardrop used any different than the other cutters?. I know my bowl scraper can be particular.
     
  17. hockenbery

    hockenbery AAW Advisor Staff Member

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    You probably don’t “need” the scraper at this point. Get really good with the tools you have. Then in a couple months or so revisit the scraper purchase.

    I have the old Stewart bars straight and curved that have screws to hold the scrapers.
    Also I have a CA Savoy 1.5” bar that has mountings for them too.

    I use teardrops similar to those that Trent Bosch sells. To use them you also have to buy a bar.
    You probably can get away with just the curved Bar scraper it will work down to dead center bottom.
    I just learned to use the straight tool for the bottom.

    I cut my own from tautung that MSC stopped carrying. Still have two left in the last bar I have.
    Then 8 may try edger blades as stock.

    I use the scrapers level and on center and pushing from rim to bottom this lets the curve of the leading ,work for you similar to pushing the gouge forward in a scraping position so that the leading edge of the lower wing can cut- back cut is one name people use for this.

    Also i finish the inside wall in 3” increments. So as get 3 inches down the wall I clear away anything that sticks out then use the scraper for the three inches being careful as i get to the end of the 3 inches in case I did not clear away everything that sticks out.
    Then do the next 3”
     
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  18. john lucas

    john lucas AAW Forum Expert

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    Many many years ago I remember reading about someone putting gravel inside to clean up the inside of a vessel. I think I even tried it but that was soooo long ago. don't remember anything about it other than if it had been successful I would probably still be doing it. I think it's the Fred Flinstone method of finishing the inside.
     
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  19. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I don't remember who did it, but as I predicted it was a disaster. It mainly eroded the softer early wood, but as the vessel started filling with wood dust the erosion just fizzled out.
     
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  20. Jason Van Duyn

    Jason Van Duyn

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    I used to sand the inside of hollow forms and I basically don't now for two reasons. Before I get to that, I used a set of forceps to hold a piece of old sanding disc wrapped around a small bit of floor mat to sand the inside of the hollows. Craft supplies sells the forcepts

    https://www.woodturnerscatalog.com/p/119/5070/turners-select-Sanding-Clamp

    Ok to the reasons why I don't sand that much anymore...

    1 - I try and shoot for opening sizes to be around 10% of the diameter of the piece. So a 5" hollow has a 1/2" opening... which means the opening is now too small. I will sand on larger pieces, with larger openings occasionally.
    2 - this is more philosophical but I would rather have an unsanded surface on the inside as it shows the skill of the turner. I do a lot of natural edge hollows, so often you can see inside of many of my pieces. Some days for better or worse.

    I saw you were asking about finishing the inside of the piece. I think it would be better to be able to immerse a hollow in a vat of danish oil, however that is only helpful if the inside can be seen. In those cases I think it looks better but again I have moved away from that as my openings are small and I can't get inside there with the forceps for finishing. I also mix my own danish oil ... https://vanduynwoodwork.com/2018/09/18/danish-oil-finish-top-3-reasons-to-mix-your-own/ ... so its expensive to have a large quantity mixed up for immersion unless you have a vaccuum pot, which I don't. The oil will eventually skim and set otherwise.

    Sanding on the inside surface is nuance really. It can have a nice feel if you can feel it but honestly outside shape and proportion are more important factors to a good hollow.

    JVD
    www.vanduynwoodwork.com
     
  21. William Rogers

    William Rogers

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    First, Jason thanks for the information you share on your website and your work is outstanding.

    I sand the inside of my hollow forms IF you can see inside easily. I also use the same instrument forcipes/hemostats as Jason, but the HF version. I’ve put some sticky back craft fun foam on sandpaper and use the hemostats. Note; don’t put your fingers in the holes of the hemostats when sanding.

    Regarding finish on the inside, I was taught by an old cabinet maker to finish both sides. His theory was that if the the would absorb moisture differently and lead to warp if only one side was finished. I don’t know if there is that much difference, but it made sense to me. If I’m using a spray finish I use sanding sealer on the inside.
     
    Last edited: Aug 16, 2019
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  22. Gerald Lawrence

    Gerald Lawrence

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    I only sand as far as someone could reach with a finger, in other words about 2.5 inches. That is only on the narrow opening forms. For wider forms starting at 4 inch opening I sand farther down or use black gesso so no one can inside. As to finish I do not finish inside deep or hollow forms such as you have shown. As to the cabinet makers comments on inside finish if you will look at real antique furniture the inside is not finished, So that will have very little effect on wood movement.

    As to the teardrop scrapers. Not that great for hollowing itself but excellent for doing a cleanup of the inside and could actually be used to get finial finish surface inside a bowl including the bottom. They can be used on curved or straight bars. I have one that is on a straight bar set at a 20 degree forward angle to get somewhat of a shear scrape.
     
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  23. Brandon Sloan

    Brandon Sloan

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    Thank you to everyone who took the time to offer tips and tricks. I really do appreciate it and will use the advice to become a better turner.
     
  24. William Rogers

    William Rogers

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    Gerald, I have a “real" antique desk and it is finished underside, back, and inside drawers. Maybe not all antique furniture but some yes. For me I’ll continue to seal/finish the inside as the only downside I can see is the time and expense of the finish. Not much IMO. I would say turners preference in finishing the inside.
     
    Last edited: Aug 16, 2019
  25. Gerald Lawrence

    Gerald Lawrence

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    When what I call real antiques were made (over 150 year) they did not do inside and there was lots of saw and chisel mark on undersides of tops and bottom of drawers. Finishing was very time consuming and expensive but of no use as far as anyone seeing and not affecting the longevity of the piece. Not true of plywood which has to have that matching veneer but finish does not affect it. The reason finish has no effect on a piece lasting is that it slows (at least some finishes do) the exchange of moisture. Now consider environment and that gets to be a long story.

    But overall it is just in makers opinion because with controlled environments that will have little effect.
     
  26. William Rogers

    William Rogers

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    Not disagreeing with you Gerald. To me I feel it is better to finish than not to finish the inside.
     

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