woodbowlsandthings

June 16, 2014

Sanding the inside of a Hollow Form

Occasionally I really want a really good finish on the inside of a Hollow Form no matter how big the opening is. An example would be when I want to pierce the form with some sort of art that would allow people to get a good look at the inside. Another might be when I make a Hollow Form influenced by harvey Fein. His work frequently has openings in the shape of slits or slots that go all the way through the piece.
To this end I read somewhere that if pieces of broken tempered glass are put inside and slowly rotated they will eventually finely finish the inside.
I am presently experimenting with this process and have rough turned the inside of a couple of blocks of Birch. I used my Kobra hollowing system and made no attempt to get a smooth interior. I did perform a final light cut with a freshly sharpened cuter. The intention was to leave some roughness and some ridges.

The blocks are about 3″ square and 5 1/2 long.
Here is a photo of the devise I cobbled together with parts I had laying around.

IMG_3160

It enables me to angle the turning if I want more finishing done towards either end. The original BBQ rotisserie motor turned twice as fast as my current one. I had planned to turn a week with it slanting towards the top and a week towards the bottom but during the process I decided I needed to keep track of revolutions rather than days/weeks.
Here is a picture of one of them prior to beginning the process.

IMG_3086

Here is a photo comparing the one on the left (unsanded) and on the right the sanded one.

This was accomplished in about 8600 Revolutions.

IMG_3165

As you can see the section on the left does have a much nicer finish and actually feels as if it has been sanded quite well. It did not however remove much of the ridges. I think I will devise a faster turning model and give it a try again. Sanding with more revolutions this time.

On another thread someone suggested the addition of marbles along with the glass and this I will try next.

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1 Comment »

  1. I think your very innovative – good luck

    Like

    Comment by Ray Smith Timaru New Zealand — January 28, 2015 @ 11:25 pm


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