Question

I have a question I hope you can answer for me. Recently, I was cutting a stone and watching it contact the lap of my Graves Mark IV faceting machine. As I moved the stone, I noticed that contact was not consistent across the width of the lap. While the stone wasn’t making contact with the lap toward the center, near the arbor, it was contacting the outside portion of the lap.

I thought the stone being cut should make contact across the entire width of the lap. Is that correct? If I need to adjust my faceting machine, can you give me some tips for completing that task?

Thanks,

Phil DeHart

Answer

Here are two IGS lapidary articles that will help you. The first, “Scratches From The Master Lap,” is quite lengthy. Nevertheless, it covers just about everything you’ll need to know about adjusting your Graves faceting machine. The other, “The History of the Beale/Woolley Depth of Cut Indicator,” covers an inexpensive accessory that will make your faceting machine more accurate.

Regarding how a gemstone should contact a lap, let me point out that a flat lap to dop swing isn’t necessary. I learned to cut that way,…