I have a 24" great Western and the hydraulics system has a throttling valve on it so that I can control the speed of the carriage depending on the material that I am sawing. It doesn't have a shut off mechanism, just a bolt on the carriage that hits the back wall to stop the carriage.
I would like to find a parts list for the saw because the throttling valve is wearing out and the carriage doesn't always move smoothly or at a consistant speed. I will probably end up taking it to a hardware store and getting a matching one.
Bob

Shawn,
Use it as long as you want. I'm having trouble getting the light evenly under the background so it looks darker in the center of the cab. The density of the transparent area is the same all across the cab. I use two 100 watt blue photo flood lamps pointing in from the sides but I need to make another stand that will lift the cab higher towards the camera then I should get a more even light under there. I use a home made plexiglas stand with double sided sticky to hold the cab in place so it is lifted away the background that makes it look like it is floating in mid air. I also use a photo gradient for the background.
Bob

It is a solid piece of Obsidian without any backing or such. It is a little thicker than I usually cut this material but the clear area had enough transparency for it to show well.
Bob

I just finished this Mahogany lace cab. It is 4" across.
Bob

I kinda got carried away with this one. It is a Brazilian Agate that is 3-1/2" tall.
Bob

Rhodochrosite

After seeing this great piece I'm almost motivated to make one for my wife's 65 GTO but I don't think she is into wearing belts with big silver buckles.
Bob

This one is a COPCO Agate cab that is a small one for me at 1" tall.
Can you see something in it?

$15 for a 12" by 12" by 1/8" sheet on Ebay
Bob

The seal is a sheet of silicone rubber. Most of them that I have seen are red. Most jewelry tools suppliers should carry it.
Bob

Actually I heat the piece under a 100 watt bench lamp until it is too hot to touch, then I place it in an aluminum muffin pan with Opticon and heat it again to make the Opticon thin and watery so it will penetrate better.  All of this heat definitely drives off all the water. I let it cool a somewhat to minimize the probability of the Opticon boiling under vacuum but it still does.
Bob

In my efforts at stabilizing or fracture sealing with a vacuum pump I found that, at least in my experience, the vacuum was so significant that what I saw as bubbles coming from the fractures was actually the epoxy boiling and causing the bubbles. I'm using an industrial vacuum pump that probably works too well.
Bob

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

Amethyst Druzy?
Bob

I've found that most opalized wood is fragile, fractures easily and rarely holds together enough to do much lapidary work on it. I would imagine that stabilizing it with Opticon might work but if it is of any size I doubt that the Opticon can penetrate very deeply. I stare at many of my pieces of this material thinking that someday I might just try stabilizing it and then I set it aside while I move on to working on other more solid lapidary material.
Bob