Back to the Tumbler
Because I do a lot of rock tumbling for the Wheels of Fortune at our club’s show, I have the opportunity to look at a lot of polished rocks coming out of my tumblers. I have one 40-pound and two 12-pound units running all of the time. Recently, I was emptying one of them after the grinding step, and I spied an intriguing piece. I believe it is a Brazilian agate mostly because of the pattern in it.
As usual, I am constantly looking for patterns that allow me to carve a sun image on the back. The piece must have a fairly translucent area where I do the carving, so the image shows through to the front. This area must be large enough to carve the sun image and not interfere with the overall image.
The existing black images are rather wispy and ephemeral within this piece, so I chose to make the rays coming off of the sun image irregular and curvy. There is an open space on the piece where the sun image will fit. I located the spot where I wanted the sun image and ground it on the back with a 2mm diamond ball bur and enlarged it with other bits and a final shaping with an 8mm bit.
Because these bits will not drill a hole very well if they are held vertically, I used the side of the bit to deepen the hole. When you drill with the side of the bit, it tends to pull towards the cutting side and makes an oval-shaped hole so frequently that I turn the bit vertically to make sure the hole is truly round. I used a caliper to determine the depth of the hole.
Because this piece didn’t have a highly translucent area for the sun image, I drilled the hole deeper than usual to show better. It is within 1mm of the front of the 5mm thick cab.
When I finished drilling the hole, I used a fine tip felt pen to sketch the wavy rays. Then I used a small diamond bur to grind the ray design. I then used a small cone bur to refine the shape. When I’m sanding the wavy sun rays, I shape a small wood dowel so that I can reach into the depth of the carved waves. I hold it against a coarse file to shape the wood dowel as it is spinning in the handpiece of my Foredom flex shaft unit. I also mix a small amount of 220 grit tumbling media in a small plastic condiment cup. When I mix it, I use very little water, so the mixture is a heavy slurry to ladle small quantities with a wood spatula directly into the carved areas. As I’m sanding, I run the Foredom unit very slowly so the grit is not slung off the dowel. As the slurry breaks down, I use my thumb to push more of it into the groove. When the groove is sanded enough, I clean the cab and wood dowel well and go to a 400 grit and repeat the process. I follow up with a clean-shaped dowel and Rapid Polish, again mixing a slurry and loading it into the curved grooves.
I repeat the same process with the carved hole until I’m finished.
As an added observation: This piece had more red tones in the open area than usual, which is why it ended up with more notable red coloring showing through the front.