Hi Niko,
Like Jim says, different gems need different care. Even different pieces of the same mineral or gem from different or even the same mines can vary.
You need a system that is flexible to your needs,affordable and easily adapted.
For boulder opal I was using a 120 grit sintered 8" wheel for course grinding, It was great on opal but a little slow on agate and others. Finally I wore it out and replaced it with a 100 grit, big mistake!! It's amazing how much more chipping this wheel caures.
Ask around at clubs and ask those who know and not rely the sales staff alone.
I also use the expanding drums but I like the 6" x 3" they are obviously wider,
they allow me not only to change grits fast they are wide enough for me to be able to cut large specimens and the smaller diameter allows me to get into some curves. They are exellent for finishing volumes of cheaper material fast.
A cheap combo unit is a good start as long as the wheels are far enough apart. ( I recomend at least 1 inch apart if you absolutely can't avoid it).
Nova wheels are great but need to be run in correctly, be careful with sharp or straight edges on you gems, they can strip weeks of use from your wheel in seconds.
I still like useing novas, but they are $240 each for 6" in Australia and thats just too expensive. I reserve these for my best gems only.
A good basic combo unit will have a 6" saw (removable) on one side, a 120 to 220 grit grinding wheel and a flat sanding disc on the end , when you can afford a seperate saw you can replace that one with more wheels.
If you go with this type of unit you must keep it clean.
Buy an extra few discs for the end and have a dedicated polishing disc (I find hard felt is best for polishing most hard gems and leather for softer).
If you can find a basic cheap mahine that takes two grinding wheels, you might like to use a180 or 220 silicom carbide or diamond wheel (slower) and fit a 280 grit nova. That will allow you to remove scratches faster and lasts way longer than paper.
Once you have become used to cutting you can add to your equipment as you make some money from sales.
If grinding knuckles is an unavoidable problem or risk I find a pair of cheap medical latex glover (around $9 per 100 pair) are good but keep them tight over your finger tip or they could become a hazard, they take a bit of getting used to but they will save you some grief . I use them when using a 6" paper sanding disk as well, if I slip I don't cut a finger and the gloves will tolerate a few swipes. If the glove tares just replace it.
I hope this helps
Regards to all from Ken
