artworkplayer
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Post by artworkplayer on Jan 23, 2007 20:39:53 GMT -5
I would think that the main advantages of 8 over 6 inch wheels would be a bit faster, cooler cutting and a bit longer wheel life, maybe more than offsetting the 30% or so greater initial cost--that the right idea, or...? It'd be great to hear from somebody who's had experience with both.  |
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Post by stoner on Jan 23, 2007 21:36:43 GMT -5
You've pretty much got the idea, bigger wheel-more surface area covered with diamond, longer life. But, the cost of the replacement wheels is greater than 30%. I use an 8" grinder and for a while I had a 6" Nova wheel I picked up for $10. I guess I'm used using 8" wheels because I never did like that 6" wheel. But it's just a matter of personal preference.
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Post by sandsman1 on Jan 23, 2007 22:48:09 GMT -5
if i was gonna use a silcon wheel id go 8 inch if i was goin diamond id go 6 inch if your gonna have multiple wheels just for the price -- dont get me wrong i have a genie with all 6 inch but i also bought a 8 inch 80 grt for my other grinder for rough shaping biger pieces but it only cost like 80 bucks i think from that place over seas --- when i replaced my genie wheels it was like 700.00 for 6 diamond wheels at 6 inch i dont even wanna know what it woulda cost for the same in 8 inch haha
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Post by freeform on Jan 23, 2007 22:54:35 GMT -5
Yup, bigger is better kinda mentale. If you want to do large cabochons, 8inch is best in my opinion.
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stefan
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Post by stefan on Jan 24, 2007 10:43:53 GMT -5
Yea 8 inch has more surface area- and should (in theroy at least) make for easy grinding (especially in the flats)
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artworkplayer
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Post by artworkplayer on Jan 24, 2007 20:31:13 GMT -5
Thanks all. Now here's a question...
Let's say I bought two 100 grit Crystalite diamond wheels from Kingsley North: a 6-inch for $160 and an 8-inch for $210 (basically 1/3 more diameter for 1/3 more $), both of them the same 1 1/2 inch width.
Now if I put both of them on the same arbor so that both revolve at the same speed--say, 1725 RPM--then the 8-inch wheel surface will go around "faster" against the gemstone, because with every one of those 1725 revolutions, 24 inches of diameter will pass by rather than only 18. BUT..
That won't be the same as grinding on the 6-inch wheel at 1/3 faster RPM, because of heat buildup: The 8-inch not only has 1 1/3 the grinding surface area of the 6-inch to take the heat; it also has almost twice as much internal area to dissipate it. So working at the same grinding speed, the 8-inch would definitely run cooler, and naturally that could translate into faster safe grinding speeds and/or longer wheel life with 8-inch wheels than with 6-inch wheels (though how much, I don't know). So here's my main question:
Are 8-inch-wheel arbors designed to revolve at the same RPM as 6-inch-wheel arbors? IOW same size pulley--anybody know?
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stefan
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Post by stefan on Jan 25, 2007 11:58:09 GMT -5
Maybe I'm no mathmatician but would the 6" wheel actually be "faster" as it smaller- and therefore closer to the center of graviety? but as for Heat dissapation- well with a properly cooled (drip of fountain) wheel- heat should not be a concern- and if it is- well then the system is not designed correctly.
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artworkplayer
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Post by artworkplayer on Jan 25, 2007 19:21:55 GMT -5
Hi Stefan. The grinding stone might think it's going faster, but the gemstone thinks it's going slower, because the gemstone is just sitting there feeling the grinding surface rub by. IOW ya gotcher shaft going at 1725 RPM, and on it both your 6"wheel (with its 18" of grinding surface) and your 8"wheel (with its 24" of grinding surface). So put your gemstone up to the 8"wheel and 3450 feet rub by it every minute, but put it up to the 6"wheel and only 2587 feet rub by every minute. I guess this is called FPM. So unlike with blades, heat isn't much concern with grinding wheels, huh? I'm glad to know that. Does keep me wondering--at 40% more cost and 80% more mass/weight to deal with, how much more quality grinding are we getting out of the 8" wheels over the 6"?  |
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stefan
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Post by stefan on Jan 26, 2007 11:14:02 GMT -5
OK my simple mind grasps what you are saying!!! I sometimes wish I had a 6 inch wheel- the belts are so much cheaper- but then I'll face polish a 3 inch wide Thunderegg slice and praise the extra width of the 8 inch- YOU PAYS YOUR MONIES- AND TAKES YOUR CHANCE
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