General information about the Site

This lapidary and jewelry design community forum is dedicated to the novice, more experienced, and expert lapidaries and jewelry designers.

Forum cabochon in the Spotlight

Bob ( bobby1 ) shared this unknown druzy

Forum Jewelry Design in the Spotlight

John shared this beautiful pair of amethyst cufflinks

Forum Jewelry Design in the Spotlight

Mick B shared this stunning opal shell carving

Intarsias / Composites / Bead Making in the Spotlight

Kent shared this really nice Imperial Jasper pendant

Lapidary Related and Forum Member Shop Links

Brian Ababurko Silversmithing Classes / Rock Rollers Club

Dons Lapidary Arts

Idaho Rock Shop

Rare Rocks and Gems

Coyote Rainbow

Lightninghorse

Rocky Treasures

Talking Rocks

Fine Gem Designs

Idaho Rockman

Fine Woodwork and Lapidary

Darkstar Jewelry

DLC Gems

Teton Art Gallery

Art Cut Gems

Woman With A Torch

Lapidary Buy and Sell (Facebook Group)

Lapidary (Facebook Group)

Lapidary Equipment Marketplace (Facebook Group)


Lapidary / Gemstone Community Forum
January 20, 2019, 01:53:40 pm
Welcome, Guest. Please login or register.

Login with username, password and session length
News:
 
  Home Help Search Login Register  

Finishing the inside of Stone Bowls

Pages: [1]   Go Down
  Print  
Author Topic: Finishing the inside of Stone Bowls  (Read 281 times)
Amethyst Rose
Full Member
***
Offline Offline

Posts: 141


WWW
« on: January 06, 2016, 03:10:31 pm »

I didn't know where to post this question for the group but carving is at least close.

I have obtained from an estate about 300 unfinished stone bowls.  These bowls were cut initinally by Dr. Martin Hulquist of Boulder Colorado and obtained from his estate by another rockhound.  He just stored them for 30+ years and now I have them.

I have no problems finishing the exterior of most of the bowls with either the Genie or expando drum unit but am looking for input as to ideas for the interior.  These are all near perfect spherical cuts from 2 inchs to 4+ inches in size.  I have been contemplating using 3M bristle brushes on my carving arbor.  They come in all ranges of grit sizes and in both 2 and 3 inch sizes.  The arbor has its own water supply so I can keep the bowls cool.

The instructions I have that were written by Dr. Hulquist spend all their time on the actual cutting of the bowls and a partial paragraph on finishing in which he describes using wood wheels on a home made flexible shaft.  Unfortunately, none of this equipment can be located.  I know where the original bowl cutting equipment is and how to use it but finding rough large enough and flawless enough to cut more bowls is problematical.

Does anyone have any other ideas as to ways to finish the interior of these bowls.

Thanks in advance

Bob Johannes
The Amethyst Rose
Report Spam   Logged

Debbie K
Hero Member
*****
Offline Offline

Posts: 1139


« Reply #1 on: January 06, 2016, 06:31:11 pm »

I polished the interior of a chalcedony cup and jade cup using large wooden craft balls. I used diamond powder and oil.

I made a point carver out of an arbor from Kingsley North and a Jacobs chuck. I recently tried to find the arbor in their catalog, but it wasn't in the new one or on their webpage. I posted a response to someones question about bowl carving and polishing, where I talked about the danger of using a flex shaft with these heavy wheels. They loosen up in collets and more than once I was holding a large stone or large wooden ball into the machine with the rock as the motor from my Wecheer wound down. Not happy making. The Jacobs chuck didn't loosen up.

You could cut a circle out of an appropriately thick piece of maple with a hole in the center and file it down while it's spinning to true it and also chamfer the edges to accommodate the concave contour of the bowl. Maple works well with the oil and diamond powder, but it will wear down. I always made an extra for the coarser grits, 100 and 200, as they lose their diameter pretty quickly. I did 100, 200, 600, 1200, 3000 and 8000. The chalcedony polished beautifully. You just spin and rotate the cup by hand; it works really well.

Here's the point carver I made, and for safety's sake I recommend making one. The flex shaft just isn't designed to hold heavy bits or burs like what you need. In the second photo, you can see a wheel in the box. It came from a Michael's or Hobby Lobby in the wood section for making wooden cars. The large wooden ball came from there also; and as this is the 600 grit box it is pretty ground down; it started out at least 1/2 again as big. The 100 and 200 grit ones are even smaller.

Debbie K


* point-carver.jpg (13.79 KB, 600x600 - viewed 8 times.)

* Untitled-1.jpg (12.94 KB, 600x600 - viewed 6 times.)
Report Spam   Logged
Amethyst Rose
Full Member
***
Offline Offline

Posts: 141


WWW
« Reply #2 on: January 06, 2016, 06:45:51 pm »

What I have is not a flex shaft.  That is what the old timer who first cut the bowls made.  What I have is the Diamond Pacific Carving Arbor with a variable speed motor and water drip with face shield.  I'll see how the bristle brushes work when the arbor adaptor comes in.  The arbor has a 5/16" s in shaft and I can't find a tapered spindle to fit but did find an adapter to bring it up to 1/2".  The wood balls look interesting as well.  Thanks for the tips.

Bob Johannes
The Amethyst Rose
Report Spam   Logged
Debbie K
Hero Member
*****
Offline Offline

Posts: 1139


« Reply #3 on: January 06, 2016, 08:34:29 pm »

In my experience the bristle brushes don't work until your last grits. They help with 3000 and 8000 to achieve a higher polish, but don't do much to remove any grinding marks. I tried them, too. Interestingly, the softer brushes work better than the stiff ones.

Debbie K
Report Spam   Logged
bobby1
Hero Member
*****
Offline Offline

Gender: Male
Posts: 3606


« Reply #4 on: January 06, 2016, 10:53:09 pm »

I do a lot of the sanding and polishing with wood wheels and tumbling grits. Get a wood ball from a hobby store and cut in half. Locate the center and screw in a large wood screw that will fit in the chuck of your fixed or flex shaft. I put the particular grit that I'm using to "sand" with in a small plastic or aluminum cup and add a little water and roll the wood ball half in it with considerable force so as to embed it into the wood. I then moisten the ball and dip it into the grit  then proceed to spin this ball around in the bowl to do the sanding operation. I have different balls for the different grits . I also use one of these for the polish either cerium or aluminum oxide. You can also cut round disks from a piece of wood and do this sanding and polishing process.
Bob
Report Spam   Logged



Pages: [1]   Go Up
  Print  
 
Jump to:  

Bookmark this site! | Upgrade This Forum
SMF For Free - Create your own Forum | Buy traffic for your forum/website

Powered by SMF | SMF © 2016, Simple Machines
Privacy Policy