RockingRuralMo
starting to spend too much on rocks
Member since July 2022
Posts: 132
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Post by RockingRuralMo on Sept 17, 2022 7:21:07 GMT -5
I'm a newer lapidary, but really enjoying the tinkering side of the hobby.
I bought an old 1950s or 60s two-headed grinder that I'm going to upgrade with modern wheels. (the carbide wheels on it now are cracked.) Your expert advice would be much appreciated.
There's room for 2 wheels. I was thinking I'd do one "coarse" wheel for rough shaping of cabs, and a an expanding drum for the other. I have questions (naturally) about both.
For the coarse wheel I'm trying to figure out ideal grit, and also ideal material.
I was thinking probably something in the 120 - 140 range, mostly because I fear that 60-80 is too coarse for my skill set, especially with softer material, and 120-140 seems to be the most common "next" range in the products I'm looking at. (My flat lap started at 180, so either one will be faster than I'm used to.)
Then for the actual wheels I was choosing between:
Nova or Super Nova wheel - I like the idea of a soft wheel for shaping, especially since I'm new to the craft and have only used a flat lap. The resurfacing option is pretty great too. I can only resurface a proper "nova" though right? Not the Johnson Brothers "supernova"? (Or am I wrong about that?)
- Solid silicone carbide green wheel (a budget option but I'm not familiar with their effectiveness, but $30 to get started is enticing.)
- Sintered diamond wheel - most expensive, not soft, but should last a really long time. I'm willing to invest, but wonder if I should wait until I really understand this type of machine before jumping off in the deep end.
- Some other thing that wiser lapidaries recommend instead?
Then on the expanding drum I'm torn about 2 things:
Is a 2.5 really appreciably better than a 1.5? I've only made cabochons - nothing bigger yet. Is it worth going ahead and doing the bigger drum? It's not much more expensive, so I'm inclined to go bigger unless there's a down side.
On belts: I was going to go with silicone carbide at least at first because they're so cheap (under $2 at Johnson Bros.) But they only go to about 1000 grit. Should I switch to diamond for a finer one (I'd like at least a 3k.) Should I just go with diamond in the first place? They're SO much more expensive. But if they last longer and do better work maybe I should just get it over with. What do you experts think?
I extend my eternal gratitude to all of you for your help. It's been a great ride so far, but there's so much great stuff out there it's hard to optimize as a new kid.
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Post by jasoninsd on Sept 17, 2022 7:47:25 GMT -5
I can't answer ALL your questions, but I will say my opinion about the first wheel. I wouldn't go with a 120 for the initial grinding wheel. Harder materials will take forever to grind...and put additional wear on the 120 which will make it wear it out faster than necessary. You are correct that softer material will require starting on the 120...so you wouldn't be able to start them on the 60-80. It's a trade off. I will say that I do WAY more initial grinding on my 80 than my 120 (due to working more harder material than softer material).
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RockingRuralMo
starting to spend too much on rocks
Member since July 2022
Posts: 132
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Post by RockingRuralMo on Sept 17, 2022 8:27:59 GMT -5
Thank You Jasoninsd! That's a good point. I like working with Jasper and Agate so the 80 may be the better route. I'm working up 30lb of sodaliate right now, but. Maybe just get a 120 expanding drum belt for those soft-rock occasions?
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Post by jasoninsd on Sept 17, 2022 14:59:24 GMT -5
Thank You Jasoninsd! That's a good point. I like working with Jasper and Agate so the 80 may be the better route. I'm working up 30lb of sodaliate right now, but. Maybe just get a 120 expanding drum belt for those soft-rock occasions? I'm hoping others with more experience with expanding drums will chime in... Another option...not saying it's the best...but what if you were to get both the 80 and the 220 hard wheels and swap them out when you're working whatever material requires whichever one. Maybe do a run of agates/jaspers for a spell...then switch to the 220 and work softer material. Something like Sodalite should never touch an 80 grit wheel. It's really soft...and has a tendency to get "chippy" if worked on the 80. My 220 cuts through it like butter anyway... Again, I'm not experienced with the expanding drums...but I wouldn't think they'd be good for "grinding" a shape...but don't hold me to that! BTW - I just happened to pop back into your thread and saw you said this to me. The best way to get someone's attention and make sure they see your post to them is to either quote their post and type your response (like I'm doing now)...OR you can "tag" someone by putting a @ in front of their username like this: RockingRuralMo - If you do this option, hover your cursor over their screen name and it'll give a little popup as to what their actual username is. Like your name doesn't actually have capitol letters in it...
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Post by Rockoonz on Sept 18, 2022 10:35:20 GMT -5
The NW Rockhound retreat uses a 180/220 hard wheel combo on the arbors they use for teaching. As stated above, with really hard materials it was way too slow, but since they started with brand new wheels every year it provided the opportunity to not have to deal with breaking in 80 grit wheels and make nice preforms disappear. I suspect that 120 grit wheels were not available from their supplier. All that said, I agree that 80 or 100 grit is what you want unless you plan to only work with softer materials. Keep in mind that a light touch on a 80 grit was the old school equivalent of a 220 grit and that many cabochons have been brought to a wet look level of polish with 2 hard wheels and some cerium on leather.
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Sept 18, 2022 18:05:22 GMT -5
If I were in your situation, I would go with a 80 grit sintered wheel from Kingsley North, it will cut less aggressively than a plated wheel of the same grit, and be far more tolerant of the occasional bit of abuse that learning new skills can bring. They are more expensive than a "cheap" plated wheel, but are pretty close to an equivalent name brand wheel, and unless you are going to be making a career of standing in front of the grinder, will last for years. From there, I would go with the expanding drum, probably with a 180 or 220 diamond belt for smoothing and refining the shape from the hard wheel. Unless you are grinding stones that are 8 or harder on the Mohs scale, silicon carbide belts work well for sanding and pre-polish. Don't be discouraged by 1000 grit being the finest belts available, SiC is a highly friable abrasive, so it acts like a finer grit. Your 1000 grit belt will leave a satin finish that can go straight to polish, either with diamond paste or your choice of oxide (cerium, tin, chrome, aluminum...) My progression lately has been 80 and 220 sintered, 220 diamond belt, 400, 600, and 1000 silicon carbide belts all with water, then dry polish with 14000 diamond paste on a resin belt or poly pad. It might be worth looking into a polishing head for one end of the shaft if your machine has space for it. The above progression produced this finish on some royal imperial jasper IMG20220829204246 by nik1924, on Flickr
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