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Post by broseph82 on Feb 12, 2015 17:38:22 GMT -5
1) How many cabs can one do on a SiC belt before it's not at it's current grit? (i.e. 200grit before becoming a 400)
2) Do I really need a 200 hard wheel? I know some of you use nothing but expandos, but sometimes it seems like it takes so long on the expandos compared to hard wheels.
3) Do I really need a 280 grit wheel or will a 320 take out the 220 just as well?
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Feb 12, 2015 18:32:46 GMT -5
The number of cabs one can get per SC belt or disc varies depending on the several factors. Size, hardness and shapes of the cabs matters, plus not all brands of SC are equal either. Back when I first learned to cab all we had were SC wheels. The common set up was 100gt & 220gt hard wheels for shaping. Then 400gt, 600gt for sanding and then a worn 600gt for pre-polishing. Then on to the polishing surface and oxide or choice. After using diamond I would never want to have to go back to using SC. Even though diamond is more expensive it is a much better value, not only in time saved, but in the number of cabs finished per dollar invested in grinding wheels and sanding belts/discs. Diamond is also much cleaner and produces less contamination issues than SC. If you like cabbing with SC you will LOVE cabbing with diamond! Larry C.
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Post by broseph82 on Feb 12, 2015 18:36:33 GMT -5
The number of cabs one can get per SC belt or disc varies depending on the several factors. Size, hardness and shapes of the cabs matters, plus not all brands of SC are equal either. Back when I first learned to cab all we had were SC wheels. The common set up was 100gt & 220gt hard wheels for shaping. Then 400gt, 600gt for sanding and then a worn 600gt for pre-polishing. Then on to the polishing surface and oxide or choice. After using diamond I would never want to have to go back to using SC. Even though diamond is more expensive it is a much better value, not only in time saved, but in the number of cabs finished per dollar invested in grinding wheels and sanding belts/discs. Diamond is also much cleaner and produces less contamination issues than SC. If you like cabbing with SC you will LOVE cabbing with diamond! Larry C. I have both actually. After reading Jugglerguy recent post it made me think do I really need a 220 hard and a 280. I do not like switching out the expandos, but some people swear by them.
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Feb 12, 2015 18:40:22 GMT -5
Are you asking about 220 SC hard wheel and 280 SC Belt on Expando? If not what is the set up configuration you mean? Larry C.
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Post by broseph82 on Feb 12, 2015 19:31:31 GMT -5
Are you asking about 220 SC hard wheel and 280 SC Belt on Expando? If not what is the set up configuration you mean? Larry C. No. I was asking is it wise to have a 220 diamond compared to a SiC belt. Answer was "yes diamond rules!" Is it necessary to have a 280 wheel to take out 220 marks? OR does a 320 suffice for the 220 marks?
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Feb 12, 2015 19:55:23 GMT -5
Diamond does leave deeper scratches than it's SC grit equivalent. So if you are going from a 220 grit diamond wheel to an SC belt then yes you may need an SC belt at least as coarse as 280 before going to 400 SC. Not sure if I have answered your question or not? Larry C.
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Post by broseph82 on Feb 13, 2015 11:20:00 GMT -5
Diamond does leave deeper scratches than it's SC grit equivalent. So if you are going from a 220 grit diamond wheel to an SC belt then yes you may need an SC belt at least as coarse as 280 before going to 400 SC. Not sure if I have answered your question or not? Larry C. Still not quite. I've been going from 80 and 100 on diamond to SiC (expandos) 220, 320,400,600 and it seems the 220 doesn't always take out all the marks from the diamonds wheels (mostly on my glass I've been working on)
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Post by deb193redux on Feb 13, 2015 11:32:16 GMT -5
You can generally double or triple grit # between steps - but the move from grinding (really shaping) to sanding/smoothing is often much closer. I would not go from 100g diamond grinding to 220. I would consider a 100g or 180g for first sanding.
IMO you do not need both 220 and 320 - in fact 220,300,400,600 is kind of all close together. 180, 320, 600, 1200 would make more sense to me.
But now you can move you 80 and 100g onto the new arbor, and put 180 and 320 diamond wheels on the old unit. Then start the expando belts at 400, 1200, 3000, 14000
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Feb 13, 2015 12:17:28 GMT -5
Okay I understand now. 100gt diamond is pretty aggressive and leaves deep scratches. Most people do their finish shaping on 220gt (SC or Diamond)or even a 360gt diamond grinding wheel before going to the sanding belts. Also what may be happening with the glass is similar to a discussion that was held a few years back on the USFG yahoo group site where some facters who were doing their rough shaping on 100 grit and 180gt laps were complaining of having scratches follow throughout the rest of the shaping and polishing process. And regardless of how much more material they cut away the scratches remained. I remember one of the members explaining that he had studied this process under magnification and it was determined that the coarse 100/180 grit diamond particles were actually scoring the surface of high silica content faceting rough in the same way a piece of plate glass would be scored for cutting with a diamond tipped glass scoring tool. And the reaction was the same as with scored glass where fractures emanate from the scores (scratches) deeper into the subsurface of the stone and continue to run deeper throughout the entire cutting process. So this may be what is happening when you do your shaping of glass on a 100 grit diamond wheel. I would suggest adding a 220 grit grinding wheel to the process. And if the 220gt you add is SC then you could probably eliminate the 220gt and 320 SC belts. When cabbing exclusively with SC the normal line of progression would be 100gt, 220gt,400gt,600gt, and then a worn 600gt for pre-polish. Back in the mid 70s when diamond wheels started becoming more affordable the normal line of progression using diamond exclusively was 180gt (grinding), 360gt (grinding), 600gt, 1200gt, and then 3000gt and sometimes 8000gt pre-polish. I think probably the reason most folks started with 180gt back then was because industrial diamond production was still expensive and the larger growth of diamond crystals necessary to produce the 80gt and 100gt wheels made them much more expensive than the 180gt. But these days when cabbing exclusively with diamond the normal line of progression is 80gt or 100gt, and 220 grit grinding wheels. Then to 280gt, 600gt, 1200gt, and then 3000gt pre-polish. I hope this helps. Larry C.
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Post by broseph82 on Feb 13, 2015 18:17:50 GMT -5
Thanks QuailRiver ! Much appreciated info. Should the top of my cab ever come in contact with the 80 diamond? I love my 80 in shaping compared to the 100 which seems like it takes forever on harder stuff, but I think on softer glass (like my slag) I should prolly skip the 80 and do 220 do shape. I'll have to get a 220 hard to really see. In my gem club I've used the 220 right after the 120 and I liked it. I really don't like the SiC belts but it's what I have for the time being and will have to deal I guess. Thanks again!
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QuailRiver
fully equipped rock polisher
Member since May 2008
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Post by QuailRiver on Feb 13, 2015 20:32:31 GMT -5
I currently use an 80gt sintered diamond grinding wheel for pre-forming and rough shaping but leave some meat on the bone for the 220gt diamond wheel to remove for final shaping. While the 80gt is much faster, doing the final shaping with it will leave deep scratches on the crown that can be tough to sand out. And I really, really HATE having to sand out deep scratches! There are a couple of other sanding belt options to SC for the Expando drums. The least expensive are Crystalbelts www.kingsleynorth.com/skshop/product.php?id=100739&catID=1140 which can be charged with the diamond paste grit of your choice. www.kingsleynorth.com/skshop/products.php?keys=diamond%20paste&catID= These are inexpensive and I used Crystalbelts and Crystalpads for many years with good results. After applying the diamond paste to the belts/pads I used spray silicon for lube. When they start getting less effective just recharge them again with diamond paste. The Crystalbelt I had charged with 600gt diamond lasted over 20 years. You just have to be sure to clean the cab very well with a solvent like Naptha in between each grit so you don't carry coarser diamond paste to a finer charged belt and contaminate it. Then the other option, which is a more expensive than Crystalbelts but less expensive than the Nova wheels, are the pre-charged Diamond Resin Belts. I used these for several years too but the last couple of times I bought these they didn't seem to last as long as they used to and are getting so expensive that I decided the Nova wheels would be a better value and switched to them. Larry C.
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Post by bobby1 on Feb 15, 2015 0:17:29 GMT -5
I use a mildly worn 100 grit diamond wheel for the first grind and then move to a well worn 100 grit diamond wheel to smooth out the coarse grind divots. Then I go to a slightly worn 60 or 80 grit S/C belt to quickly get the shape and most of the dome material removed. I then go to a worn 220 S/C belt run dry to finish removing any grind or sand marks. This is followed by a slightly worn 400 belt run dry to get the final shape. Then to a well worn 220 and 400 and off to the polishing wheel. I learned many years ago on S/C wheels and belts. Early on I graduated from the split wheel "thumper" wheels to the expandos. After the price of diamond wheels started coming down I went to them. I feel quite comfortable with my method and the belts last me many years and they are still cheap. I am currently writing a monthly article for Rock and Gem about how I make my very large cabs with S/C belts. The first two articles have appeared in the January and February issues. Bob
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QuailRiver
fully equipped rock polisher
Member since May 2008
Posts: 1,640
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Post by QuailRiver on Feb 15, 2015 2:54:31 GMT -5
I use a mildly worn 100 grit diamond wheel for the first grind and then move to a well worn 100 grit diamond wheel to smooth out the coarse grind divots. Then I go to a slightly worn 60 or 80 grit S/C belt to quickly get the shape and most of the dome material removed. I then go to a worn 220 S/C belt run dry to finish removing any grind or sand marks. This is followed by a slightly worn 400 belt run dry to get the final shape. Then to a well worn 220 and 400 and off to the polishing wheel. I learned many years ago on S/C wheels and belts. Early on I graduated from the split wheel "thumper" wheels to the expandos. After the price of diamond wheels started coming down I went to them. I feel quite comfortable with my method and the belts last me many years and they are still cheap. I am currently writing a monthly article for Rock and Gem about how I make my very large cabs with S/C belts. The first two articles have appeared in the January and February issues. Bob Respectfully Bob, I would like to point out to any novice lapidary hobbyists reading your post the dangers of grinding or sanding dry. Inhaling particles of rock dust can cause silicosis. Even if a dust mask is worn while doing the actual cutting, without a sophisticated air cleaning system, the silica containing rock dust settles everywhere in the shop and remains a health risk when disturbed enough to become airborne again. I know of two people who have died from breathing rock dust. Larry C.
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