Post by bobby1 on Oct 8, 2008 8:39:30 GMT -5
Here are some pictures of a mini sphere maker that I built.
I mounted a motor with the shaft pointing up, installed a plastic pan to catch the debris that flys off the spinning cup and installed a jacobs chuck on the shaft.
Here is a side view of the cup. It is made from a 1" diameter steel shaft with a screw (it doesn't have to be threaded because it goes in the jacobs chuck, but I built it with a 1/4-20 thread so it will fit on the shaft of most small flat laps), and drilled a cup shape in the opposite end.
An end view. I used a large drill bit to make the recess in the end of the cup. It doesn't have to be a perfect hemisphere shape to start with because it will eventually will wear to that shape. This one is nearing that shape.
A view of how you hold the sphere while it is being ground.
I start by making a cube with the trim saw. Then I hand grind it to as close as I can to being round. Then I dip it into some water and a small container of coarse tumbling grit and hold it in the spinning cup. You rotate it around and keep dipping it in water and grit. I wear a tight fitting rubber glove because the grit will stain your fingers black really quickly. Keep grinding, inspecting for flat spots and moving to a finer grit until all of the flat spots are gone. I finish with 600 grit.
I then dop the sphere.
Then I polish it. I have to redop it a couple times to get the whole surface polished.
For larger or smaller spheres I make the cups with different size round steel shaft material.
For star material like this Rose Quartz you can align the star on the top and cut the sphere perpendicular to the star and have two star cabochons.
Bob
I mounted a motor with the shaft pointing up, installed a plastic pan to catch the debris that flys off the spinning cup and installed a jacobs chuck on the shaft.
Here is a side view of the cup. It is made from a 1" diameter steel shaft with a screw (it doesn't have to be threaded because it goes in the jacobs chuck, but I built it with a 1/4-20 thread so it will fit on the shaft of most small flat laps), and drilled a cup shape in the opposite end.
An end view. I used a large drill bit to make the recess in the end of the cup. It doesn't have to be a perfect hemisphere shape to start with because it will eventually will wear to that shape. This one is nearing that shape.
A view of how you hold the sphere while it is being ground.
I start by making a cube with the trim saw. Then I hand grind it to as close as I can to being round. Then I dip it into some water and a small container of coarse tumbling grit and hold it in the spinning cup. You rotate it around and keep dipping it in water and grit. I wear a tight fitting rubber glove because the grit will stain your fingers black really quickly. Keep grinding, inspecting for flat spots and moving to a finer grit until all of the flat spots are gone. I finish with 600 grit.
I then dop the sphere.
Then I polish it. I have to redop it a couple times to get the whole surface polished.
For larger or smaller spheres I make the cups with different size round steel shaft material.
For star material like this Rose Quartz you can align the star on the top and cut the sphere perpendicular to the star and have two star cabochons.
Bob
X - Thou shalt not covet thy neighbor's rocks
- O Henry