rockhound97058
freely admits to licking rocks
Thundereggs - Oregons Official State Rock!
Member since January 2006
Posts: 760
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Post by rockhound97058 on Jan 5, 2011 0:11:08 GMT -5
Sometime ago I planned to create a page on my website to explain various lapidary tips and equipment usage, however time and many other chores got in the way and never finished them. Below is a short video of my sphere machine actually grinding a sphere. Thought the folks who've never seen a machine actually run might enjoy it. Please note it does have sound, so turn down your speakers
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chromenut
fully equipped rock polisher
Member since December 2009
Posts: 1,971
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Post by chromenut on Jan 5, 2011 0:15:58 GMT -5
I don't know why, but I could sit there for hours watching that. Just really intrigues me. Question - how close to totally round do your preforms have to be to put them in the machine? I have a bunch I bought but they are like maybe 16 or 24 sided, something like that.... Here's one:
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rockhound97058
freely admits to licking rocks
Thundereggs - Oregons Official State Rock!
Member since January 2006
Posts: 760
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Post by rockhound97058 on Jan 5, 2011 0:26:00 GMT -5
My relative and teacher to make spheres, swore you have to have an absolute perfect blank to start with. Well in his case he would take a blank such as you have and put it directly into the machine and start grinding. I myself cut the blank (26 cuts) and then I use a 4" grinder with a dry diamond cup and I hand grind all the corners. by doing this I can eliminate time and shape my blank back into whack if need. Over the years I've had a couple preforms I've mis measured and cut a funky face and I managed to produce a great sphere, just took much longer to grind and turns out smaller than planned. The blank you have there - I see no problem to grind the corners and make that baby round! The only problem you might face with that specific blank is - if it has any hardness differences between the minerals it might undercut a bit. The worst sphere I evern had was one I bought wholesale and it was another "made in china" - That thing was so bloomin out of round. But for $6.00 for a finished sphere, I guess I shouldn't have expected more LOL. Jason
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chromenut
fully equipped rock polisher
Member since December 2009
Posts: 1,971
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Post by chromenut on Jan 5, 2011 10:03:21 GMT -5
Thanks Jason. I need to get my grinder out, shouldn't be too hard to cut these down on a 6" grinder, at least not to knock off all those corners. Thanks for the advice, I've got a dozen preforms sitting around waiting to be turned into spheres and just taking my time getting them to that point.
Oh, how long does it take to go from that rough preform to a polished sphere? Just curious.
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rockhound97058
freely admits to licking rocks
Thundereggs - Oregons Official State Rock!
Member since January 2006
Posts: 760
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Post by rockhound97058 on Jan 5, 2011 11:52:08 GMT -5
Really depends on the material for a time line. Of course material such as Obsidian or Onyx will grind much faster than brazilian agate in the machine - so it really depends on each sphere you tend to finish.
My steps are -
1 - 60/90 grit -grind untill sphere shape with no flat spots. This could take a few hours, or I have a sphere in my collection which has right at 40 hours of rough grind alone hehe! One hard piece of rock.
2- 220 grit - I switch cups and run a minimum of 2 hours
3- 600 grit - Here I change to PVC Cups and I use a jar with a grit / water mix, and use a paint brush to apply to stone as needed. At this stage you really have to stay with the machine and babysit it. Again run for a minimum of 2 hours
4 - Polish. I again use PVC Cups, but with leather pads over the ends, held in place with hose clamps. I use French Cerium or Super Cerium depending on what your supplier calls it... and I polish until done. I have had material polish in as little as 30 minutes, or I've had others take hours and various types of creations with mixed polishes. Also I do the same thing - Mix polish and water into a paste and apply with a brush to the sphere as it's tunring.
If you have one sphere machine such as I do - The most important thing is be very clean between each grit. All it takes is one grain of 60/90 to drop into your 220 or 600 grit to screw thigns up and have to start over. I usually use shop vac and a air compressor to blow the machine off... then I always wipe down with a rag before I start each grit.
Jason
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Post by jakesrocks on Jan 5, 2011 13:01:40 GMT -5
Gotta love that sound. I turned my volume all the way up. Can't wait until I've saved enough for a new sphere machine. Do you do any sort of special prep to your bell reducers, or can you use them straight from the hardware store ? Don
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Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Jan 5, 2011 13:32:01 GMT -5
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Post by Jack, lapidaryrough on Jan 5, 2011 13:50:51 GMT -5
if the sphere is cutting slow in the cups, Flat spot the sphere with Dime size flat spots on surface.
On my Sphere machine i only use ( 80 grit ) for the first course run.
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rockhound97058
freely admits to licking rocks
Thundereggs - Oregons Official State Rock!
Member since January 2006
Posts: 760
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Post by rockhound97058 on Jan 5, 2011 18:08:17 GMT -5
Good tip Tim. I've always thought about trying diamond as that's the "new age" way of cutting spheres along with core drilling them. However I know a few people who cut spheres especially John down at Richardsons can't do certain spheres with diamond - Obsidian and Labradorite are two he said the diamond is too aggresive on.... Which obsidian is one of my best producers. If you have time, I'd like to see a photo of your cups though! Don - The only special thing I do to my cups is dob some anti-seez compound into the threads... Trust me the first time you let the machine sit and the cups rust into place you'll wish you had! Other than that, nothing. I buy a bunch of various sizes and go for it. They'll last for awhile and it's best to have a set of cups for each grit. Personally myself I actually use the same set of cups for 60/90 and 220 but I take a great gamble with contamination. After I use them I usually take a pressure washer and a stiff wire brush and clean the cups very well, and I also mark the cups for which shaft they were attached to. This way I can keep the same adjustment on the machine towers and keep the sphere turning the same. Just something I found that works well for me. So far knock on wood I've never had any contamination doing this, but there's always a risk. Lapidaryrough - Not to sound thickheaded (today it's a bit worse due to other reasons lmao!)- but I'm a little confused about your tip.... If the cups are cutting slow, place dime sized flat spots on the sphere? The goal of grinding is to eliminate flat spot and turn a smooth sphere. What purpose does reintroducing flat spots gain you? On certain materials if it seems to take forever, I usually stop the machine clean the cups and start grinding again. If this fails, I usually max out spring pressure on the towers and dump the 60/90 to it lol. Can you explain more detail on your note? Thanks much! Jason
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Post by jakesrocks on Jan 5, 2011 19:02:49 GMT -5
Thanks for the info Jason. Since bell reducers aren't all that expensive, I'll probably buy a set for each grit and color code them. Tho it would be nice to have diamond cups, most of my cutting will be for myself. I may occasionally cut a sphere for a friend. I'm retired, so time spent on a sphere is no problem for me. I figure that I can buy a whole bunch of bell reducers in 2 or 3 sizes for the cost of one set of diamond cups. Don
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Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Jan 5, 2011 19:43:42 GMT -5
`Here is a pic of a sphere cup I brazed up, I have bell reducers of all sizes brazed up with 50-60 and 220. I made a few obsidian spheres with no issues at all, I use the hard diamond up to 220 then I switch to the diamond pads. BTW, the diamond brazing rod is a bit tuff braze, it is hard to get it to flow well without a lot of flux, especially the 50-60 grit. Tim Here is the velcro cups.
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chromenut
fully equipped rock polisher
Member since December 2009
Posts: 1,971
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Post by chromenut on Jan 5, 2011 20:26:20 GMT -5
What you guys are talking is so way over my head, but so interesting. One day I want to have one of these machines, seems like something that would hypnotize me for hours on end....
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rockhound97058
freely admits to licking rocks
Thundereggs - Oregons Official State Rock!
Member since January 2006
Posts: 760
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Post by rockhound97058 on Jan 6, 2011 0:29:04 GMT -5
Hey Don - Keep in mind you'll need a set of cups for each size sphere you do as well. I usually go and buy several sets of 3 and I just toss them all into rubbermaid totes and keep each grit cup together.
Thanks for the post Tim - I have seen something close to that with the diamond pads. Never tried them on a sphere, but I have many of those pads I use with my wet-stone polisher. I believe I have 30 grit upwards to 15,000? Maybe one of these day I'll get ambitious and try it out. How much larger do you run the cups that the sphere? Looks like these would work better to get the sphere farther inside the cups and get more surface area with the pads?
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lonetreestudios
starting to spend too much on rocks
RIP Rodney, AKA @lonetreestudios
Member since December 2006
Posts: 168
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Post by lonetreestudios on Jan 6, 2011 8:41:15 GMT -5
The rule of thumb (that I have heard) is for the cutter cups to be 2/3 the desired finished size of the sphere. My personal experience (with mostly 2 head machines, even more of an issue for 3 headers) is that this works as it allows quite a bit of "manipulation" of the driveline angles to allow for more / less pressure on the cutting action (without the cups fouling each other). Hope this makes sense..
Rodney
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Post by Jack, lapidaryrough on Jan 6, 2011 20:20:26 GMT -5
Rough grinding flat spots on a slow cutting surface . our a smooth surface on the sphere well increase the cutting speed of the cups. i use a covington two cup. and a smooth sphere break the grit down, to have a the surface rte-roughed up increase`s the cut speed. i know your where your coming from as i have been cutting spheres for decades on this old two cup machine.
Ken White, At Whites lapidary in Lebanon Oregon. Said i would cut faster on Mexican coconuts. I was burning up the grit on the surface edge of the cutting point on the rock, Sphere, Though i`d like to find a few more Covingtons to turn into three cup machines. Enough said.
A old tip i thought was a good one.
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