Using Copper Laps to Cut With Diamond by Sumner Olsen
Originally Published in the United States Faceter's Guild Newsletter
This article had its genesis at the 1999 Northwest Faceter's conference at Kennewick, Washington when Jack Gross sat down with me while I was demonstrating a new faceting machine. I told him about my habitual use of copper laps and how it started after I cut my first faceted gemstone egg. My first egg was a 910 carat Citrine egg with 1080 facets. I wore out a brand new 100 grit diamond lap that cost me over $180.00. Wanting to try faceting another egg I figured I had to find a more economical approach to cutting such large stones.
Going back in my memory to when I first started faceting in 1963 I decided to try something I had used before and something commercial cutters had used for a great many years---diamond charged copper laps---an economical solution to an expensive problem. Since that fateful day I have been using copper laps charged with diamond for all my rough cutting. I used and still use the original laminated lap I started out with. This lap cost me about $50.00 and I have used less than $50.00 worth of diamond bort since I started cutting with it. To date I have cut an additional twenty-two eggs, fifteen of which are shown on my web page Olsen's Omelet,and the lap shows no sign of wear because I keep it well charged with diamond. I have also roughed out many other stones on the same lap. The only down side to using copper laps is the necessity of a good cleanup between grits. To me this is a small price to pay for the cutting I do.
Recognizing the problems associated with use of ceramic and other laps when polishing Sapphire I decided to give copper a try for polishing too. To make a long story short I now polish all my Sapphires with 50,000 diamond and I couldn't be more pleased.
As Wykoff points out in his book the Technique of Master Faceting, use of copper laps has declined compared to new diamond laps due to their heaviness, slower cutting speed (?) and difficulties in maintaining a flat surface over the life of the lap. I have found the cost of solid copper laps these days to be prohibitive and therefore I have gone to the use of laminated laps or as some call them "circuit boards". With these weight is not a problem, cost is no longer a primary consideration and as far as the difficulty in maintaining a flat surface goes, the fact that I have cut twenty-two eggs as well as other stones on the one lap without noticeable signs of wear would seam to belie this as a problem area as well. The secret to eliminating these problems is keeping the lap well charged. If you see a trace of copper on your facet it is time to recharge your lap. To me there is no such thing as overcharging your lap.
How do you go about preparing your lap for use could very well be the main factor that will determine whether you will continue to use copper or not.
Remembering the affinity diamond has for petroleum products I felt I had to find a different carrier when applying diamond to copper. I found what to me has been the medium for applying my diamond bort. I prepare a mixture of diamond powder and Prematex Industrial Super Lube which is a multipurpose Synthetic Lubricant with Teflon. I thoroughly mix about three carats of diamond with the equivalent of one liquid ounce of grease. While the grease does not ball up with diamond like petroleum products do, I make sure to mix the items well. Mixed and applied in this manner it is much better than trying to apply in powder form. Before applying the mixture I lightly score the lap with a commercial scoring tool (no hacksaw blades, knifes, or razor blades please) If you don't have the correct scoring tool it is better to apply the mixture directly to an unscored lap. Just use your finger and spread a light coating of the mixture all over the lap. You can use an agate or an old wheel bearing to roll the diamond into the lap, or as I do a large sapphire crystal (not gem quality). When I use the lap I use a light drip of water to get rid of the swarf.
This covers the basics needed for you to save money on your laps as well as rapidly rough out your stones.
As a testimonial for the use of copper laps I will partially quote an e-mail sent to me by Jack. "Following our conversation at Kennewick concerning copper laps I've been using them with remarkable success. They have changed my whole attitude toward faceting---from frustration through prepolishing stages to considerable enjoyment."
An item of interest - The Dare-Devil Faceters of the Intermountain Faceter's Guild have used copper laps to preform all their "BIG" stones such as The Lady at 44,472 carats, Miss Lemon Drop at 22,951 carats, Sun Princess at 14,812 carats, the Countess at 12,678 carats as well as others.