woodbowlsandthings

June 28, 2014

Re-cobbled

The continuing saga of my path to discover an ‘easy’ way to sand the inside of hollow forms.
If you read the previous post and are following along then here is the next edition.

I previously purchased a rock tumbler at a garage sale this is a much faster turning devise than either of the BBQ motors I was trying earlier.

With the increase in speed I can in two days get the same revolutions I was getting in 2 weeks. I do realize that at some point if it spins too fast the glass will just cling to the outer walls and not tumble or grind the inside of the hollow form as I intend to.

The rock tumbler uses a 1725 rpm motor connected to a 1.5″ dia pulley which is then connected with a vee belt to a 9″ pulley. Please feel free to correct me if I’m wrong but by my calculations this devise now spins my hollow forms at  287.5 RPM. I wondered if it might be too fast but I can hear the glass and marbles (yes I have included marbles this time around) sliding and grinding as it spins. I am certainly not a machinest and the part that is in between my chuck and the shaft of the pillow block is not a tight fit and as a result the chuck ‘wobbles’ a little which i believe may add to it’s ability to sand.

Here’s a shot of my ‘re-cobbled’ devise.

IMG_3203

I tip it slightly toward the bottom and alternately the top in an attempt to get the glass and the marbles working more on the ends where the torn grain is. I try to tip it about about 2″ and run about half time with it tipped each way.

Here is a comparison shot of one piece before sanding and after about 300,000 rotations.

IMG_3210

And a closeup of the one on the right.

IMG_3208

I think you can see quite an improvement as far as sanding and removal of ridges goes but as you can see it hasn’t cleaned up the torn end grain.

If I was to do a finished Hollow form I would spend a little more time with my tools to try to minimize the torn grain prior to using my sanding devise.

Please feel free to email me if you have any comments or questions.

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