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Post by shivan on May 10, 2016 14:04:39 GMT 10
Thanks for the info Scott. I have been careful not to cross contaminate my laps, but when i recieved the machine the laps with it were not in the best condition, so iam making the best of what i have for now. The cutting discs i am using are thin toppers on a magnetic master lap, i believe they are coated but i could be wrong. Got a couple more cutting laps with the machine but have not used them as yet. For pre polish all i have is a phenolic lap that is badly scoured. On this i use a little sowing machine oil with 14, 000 diamond powder. For polishing i am just using a chromium oxide ultra lap on my aluminium master lap. So hoping to see a big improvement when i can afford a decent pre-polish and polish lap. Have managed to finish off a couple more stones in my spare time. I am getting a better idea now of where the facets should meet, and even though they are not perfect, i think i am improving. The darker stone is a garnet, with light behind it and in the rough it is a purple rock, but after it was cut is looks almost blood red with light from the top in some angles. Pity i don't have a decent camera
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Post by Flying Scott on May 10, 2016 17:07:25 GMT 10
I do hope you are open for criticism. I see in your photos the facets don't meet. But that will come with experience. have a read of this, I tryed to keep it simple.
faceting I do it my way. I sugest you start by practiceing with quarts, because inexpencive. The angles I will be using here will be for clear quartz. We are using a 96 notch index gear, 96 will be zero for this exercise. First I attach the stone I intend faceting to a dop with a 2 part epoxy resin, the dop is then inserted into the chuck , I use aluminum dops. I don't use wax to stick the stone to a dop. If the stone becomes warm the wax has a tendancy to go soft, God knows where the gem goes when it flys off from the dop some I have never found. Before I start to cut the facets on a gemstone I first set the spindle horizontal to the lap and form the gem into a cylinder. ( keep in mind the size of the cylinder will be the diameter of the finished stone) = 2 mm, 2.5 mm 3mm 3.5 mm so on so on, whatever the stone will accommodate , 6mm is "roughly 1 karat" As I said in a previous post I cut the crown first. After I have formed the cylinder I will set the spindle shaft at 45 degrees and use a 45 deg. conversion dop which will accommodate the dop that has the gem attached = the table of your gem will be flat on the lap. Cut and polish the table, first using 100 grit diamond, this will leave the table looking rather dull, thats ok, change your lap to 400 grit, clean the stone with to methylated spirits on a tisue to remove any contaminants, introduce the gem to the 400 grit for a few seconds , check how its going, after change to 1.800 grit again cleaning the gem. now its time to polish the table with 100,000 grit after cleaning the gem. lightly introduce the gem to the lap, check every 5 to 10 seconds, continue untill the table is totaly polished. Remove the 45 deg. conversion dop you don't need it again on this stone. Now insert the dop with the stone into the chuck, set angle to 45 deg. cut 8 main facets starting at 0 = 96 grind off about 40% then do the same at index 48, do same at index 24 , 72, 12, 60, 36, 84, , check that table will be 60% of crown. do regular checks with your dial guage.. Now set angle to 30 deg. for star facets, index settings 6, 18, 30, 42, 54, 60, 78, 90. Very important all of those facets must touch = meet point. now for the girdle facets. Set angle at 48 deg, index settings, 3,9,15,21,27,33,39,45,51,57,63,69,75,81,37,93 you can do all these facets using lap with 400 grit, 1,800 grit. now polish all the facets in reverse with 1000,000 grit. If you have problems I will share my knowlage. ( which is limited ) That's it, I will talk about transferring to pavilion another time
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Post by shivan on May 10, 2016 20:58:20 GMT 10
Cheers Scott. Criticism is most welcome. I have not been able to get to the club for any faceting lessons yet, so it is helpful hearing from people who know what they are doing where i have gone wrong. I do realize my facet meets need work, to start with i was trying to get them the same size by eye, till i realized that was not the way to do it. Hopefully i will get there.
Thankyou again for the info.
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Post by shivan on May 15, 2016 20:55:36 GMT 10
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Post by Flying Scott on May 15, 2016 22:15:30 GMT 10
It is very dificult to take good photos of gemstones. I did mention in my last post I never use wax to dop my stones I use a 2 part apoxy called TITE-ON To get the stone off from the dop just warm the dop with a sigarette lighter the crown should be about 1/3 of total hight of the gem. When I started cutting I used cerium oxide as a polishing agent. 100,000 grit diamond is the best, bit more expensive, cerium oxide is ok for softer stones. If you want the full range of cutting indexes and angles. I can give you that Flying Scott
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Post by shivan on May 16, 2016 0:02:50 GMT 10
Thanks again for the info. The epoxy iam using is TITE-ON, it came with the machine and has worked well up to now, but i believe it may been because i forgot to clean the stone. Have been looking round and seems like you cant but TITE-ON any more.
As for size, i am cutting a little blind there. Still working out what sort of cut work for what sizes.
Would be most interested in the cutting indexes and angles, cheers.
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Post by shivan on Jun 6, 2016 12:08:19 GMT 10
Have cut two small feldspars, one an emerald cut and the other a modified square cut. The emerald was very frustrating to do due to the size. It did not come out perfect, but was a bit of a leaning curve. Not the greatest photos, will try again with a proper camera later.
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