Bruce used to make the Transcriber brand replacement styli for Hi Fi/stereo cartridges so they are not strangers to making styli.
Please know and understand this is to answer the following question. At one time the thought an Edison diamond was worn or broken never entered my mind because I did not understand and the purpose of this post is to give understanding. I enjoy reproducer questions because it allows me to have fun with the research I and others have done.
So, how can it possibly be then, that a diamond riding over a smooth, soft, phenolic resin disc turning at a slow, slow 80 RPM can be damaging any diamond?
The answer is one revolution at a time courtesy of friction. Even modern diamonds playing vinyl with a few grams weight get worn. Think of the poor Edison DD diamond with the heavy weight and you will get the idea.
I thought diamonds were forever and as a result I lost over $500 because I purchased diamond reproducers at top dollar with worn, broken and broken and work styli. Please see the photos below to see worn and broken Edison diamonds courtesy of Ron L'Herault.
There are two types of diamonds, at least for our discussion. Gem Grade diamonds and industrial diamonds. If you do not know what Bort is then you should read this. Bort or boart is a term used in the diamond industry to refer to shards of non-gem-grade/quality diamonds. In the manufacturing and heavy industries, "bort" is used to describe dark, imperfectly formed/crystallized diamonds of varying levels of opacity. The lowest grade, "crushing bort", is crushed by steel mortars and used to make industrial-grade abrasive grits. Bob Waltrip accused one company of using material not classified as industrial diamond for making their styli.
The photo of the bort shows a mixture of bort and gem diamonds. Some of the early Edison diamonds are large and white, the later ones are small and dark.
http://en.wikipedia.org/wiki/Bort
When you think of a diamond you think of your mother's diamond ring and might be tempted to talk to a jeweler about diamonds and if you do you will get a jeweler's perspective on gem grade diamonds. Polishing a faucet that was on the diamond in your Mother's ring is much different that wearing the tip of a diamond that is .0035 in diameter. 20 pound printer paper is .0038 thick to give you an idea of the tiny surface speeding along at 80 rpm. You get wear not visible to the naked eye but thanks to Ron L'Herault you can see the wear.
Do sapphires wear? Anyone who has a Model H sapphire that has played celluloid cylinders will tell you that they do wear, you can see this wear with a loupe and hear it with degraded sound and eventually an echo and very low volume. We all accept that sapphires wear.
Diamond is the hardest known natural material on the Mohs scale of mineral hardness, where hardness is defined as resistance to scratching and is graded between 1 (softest) and 10 (hardest). Diamond has a hardness of 10 (hardest) on this scale and is four times harder than corundum, 9 Mohs. Diamond's hardness has been known since antiquity, and is the source of its name.
Ruby and Sapphire are scientifically the same mineral but just different colors. Ruby is the red variety, and Sapphire is the variety that encompasses all other colors, although the most popular and valued color of Sapphire is blue. Sapphire is also only used to describe the gem variety, otherwise it is simply called Corundum.
If sapphires wear and diamond is four times harder than sapphire it is reasonable to deduce that diamonds wear also but at a slower rate. In fact this is the reason they made the stylus microscope which is very hard to find today because few people use vinyl records these days.
I have seen hundreds of Edison diamonds and I estimate that only 5% of the original Edison diamonds are still good because of wear or the fact that they are broken. The gem quality diamond and the industrial diamond are quite different, but remember people used to use a hammer and chisel to separate diamond to make smaller stones.
Edison used to plate bare diamonds with silver and solder them into the cup on the stylus bar, I have found 5 like this. The one was so badly broken that only 20% of the original diamond was left. Edison found that these diamonds were easily broken by careless lowering of the reproducer so he created his diamond assembly. I will post the excerpt from EDAR by Ron Dethlefson next which explains Edison's diamond assemblies and how they are made. I will also post how to be careful with your Edison diamonds. I have broken Edison diamonds and know of people that have.
I have removed many of Edison's diamond assemblies and due to a lack of tolerance many are both press fit and soldered in place, only a few will push out when heated. Edison diamond assemblies are supposed to be around .074 but all vary in circumference to the extent it is easily seen with the naked eye.
The only people I have seen wear out diamonds are Larry and Bob Waltrip. If I remember correctly Bob told me an Edison diamond was good for around 450 hours. He went through at least one a year as he listened while he worked on reproducers. Most people do not play enough records to wear out even sapphires today, so far no one I have rotated a sapphire for has asked for another rotation.
The reason I am having different people test the diamonds is the same reason I have my wife do the final sound test when I rebuild reproducers.
I want to be 100% certain the diamonds are good. That is why I chose Larry to test the first one in this batch. Larry is the only person I know who plays so many DD records and I trust him as he has been my good friend for years. This is the third batch, the first two did not turn out well so Bruce continued to improve them.
There are many people to thank for the Bruce diamond project. Ron L'Herault, Larry H., Charles Smith, Rob Lomas, and Scott. Without all these people helping me nothing would have been accomplished. I would run out of space if I listed all the people who have helped me and many who did will read this and thanks to you as well.
If this does not work out it is better to shoot at a target and miss than not try at all. I really appreciate this Forum and all those who make this a such a wonderful hobby.
The bottom broken stylus is an original Edison that belonged to a man named Bruce