nmchris
starting to shine!
Member since January 2015
Posts: 26
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Post by nmchris on Mar 31, 2015 13:40:17 GMT -5
hi guys, I need some advice please. I have been trying to make cabachons. I have a Lortone lu6x with a silicon carbide wheel and sanding drum with SC belts and I am working with wood opal and petrified wood mostly. Also some common opal. First off a question about contamination from the different grit sizes. Okay it is a pain already to have to let the silicon carbide wheel spin dry for ten minutes before turning the machine of to switch wheels. I only have to do that for the first stage but still a pain. I am using a drip system, after I get the rough sanding done it isn't as much of an issue I can just stop the machine right away to switch the grit on the sanding drum. Am I supposed to be completely draining the water and clean the reservoir everytime I switch to a different grit? I mean that just seems ridiculous. I don't think I am having problems with contamination but I've read about it and I'm just wondering how to prevent it on the machine I'm using. I don't really like to do a dome shape on every cab I make, a lot of the time I do a free form and just bevel and round the edges really good but most of the surface is still flat. After polishing it isn't like looking at a flat face, there are several different "faces" of flat surfaces and it really looks bad because the light bounces of each surface in a different direction and really makes the imperfections stand out. It isn't scratched up but the surface is not perfectly flat and the light does not run across it like it should. Plus with this lortone it is silly to do one cab at a time with all the wheel changes going on, so I usually try to do a bunch in each stage. The end result is frustrating because I end up with ten cabs that are not looking good at all. At first glance they look good, my friends are pretty impressed, but any one who is familiar with lapidary work would right away know it was crap. Do you guys have any advice so I can correct whatever I am doing wrong here? Thanks
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nmchris
starting to shine!
Member since January 2015
Posts: 26
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Post by nmchris on Mar 31, 2015 13:48:29 GMT -5
Thought I would also add that I have pretty much given up on dopping the stones. No matter how I heat the stone up and with repeated attempts almost as soon as I touch the stone to the sanding drum it pops right off. There have been a few times where it has stayed on for a few minutes but everytime I have tried to dop I have to come back inside and re glue the stone several times during the process. I have tried the sanding drum in every position possible and it still is not stable like the SC wheel is. It shakes to a certain degree, one side feels a little smoother while grinding, but the other side of the wheel bounces the stone around too much.
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Post by pauls on Mar 31, 2015 15:59:36 GMT -5
"Okay it is a pain already to have to let the silicon carbide wheel spin dry for ten minutes before turning the machine of" I'm not sure that this is necessary, ten minutes wow, If it was me I would be turning the water off and changing it, its not going to be saturated all the way through, just in case its got some water in it and to stop it pooling in one side of the wheel store it flat and uncovered to let the water dry. Always stand to one side when starting the wheel anyway, its good practise. But why are you changing wheels? "First off a question about contamination from the different grit sizes" Contamination is always a problem when using Silicon Carbide grinding wheels, they chuck grit everywhere. Have you considered getting a diamong grinding wheel, in the long run they aren't much dearer than SC because they last so much longer. They don't throw grit all over everything either. I would say that its probably necessary to clean up pretty well after the SC wheels. not so much between the sanders but certainly before polishing. I have my polishing wheels at the opposite end of my workshop to the grinding to stop contamination. Your dopping problem. You talk about regluing, what are you using to stick the stones on the stick? I use wax and very rarely have a stone come off, I can think of a few reasons why they aren't sticking, clean the back of the stone with methylated spirits to remove any oils. heat the stone to about the point where you can pick it up but need to put it back down again fairly quickly ( good for pet wood, Agate but too hot for opals and some other stones) if you put a tiny grain of wax on the stone you should see ot getting soft. presumably you have a blob of wax on your stick already, heat it slowly till its soft all the way through but not dripping off then a quick pass into the hot part of the flame to get just the outer layer really runny then dob it onto your rock, mold it to shape with wet fingers then when cool enough to move just pass it through the flame again, let it cool slowly, this is very important, if you cool it quickly the stone will contract at a different rate to the wax and peel off. Don't use one of those wax heaters they over cook the wax and boil off some of the sticky compounds. Burnt wax is useless. I use a tobacco tin (or cat food tin) if I need to heat up a quantity of wax over a spirit flame, I never get the whole tin cooking though unless I am adding extras to the wax. What extras? A bit extra shellac helps make the wax stickier, a small amount of Plaster of Paris acts like an agregate in concrete and binds things together, generally I don't need to play around with the wax unless I am forced to use ordinary sealing wax from the office store. If you are still having trouble with the wax not sticking to the stone make up some shellac and spirit mixture in a small jar and just paint a bit of that on your stone before sicking it. If you keep the shaped wax from your last stone on the end of the stick (after you have popped the stone off in the freezer just leave the wax on the stick)then its a really simple matter next time to heat your stone pass the flat surface of your waxed dopstick through the flame then just stick it on your stone it takes just seconds and will not come off.
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nmchris
starting to shine!
Member since January 2015
Posts: 26
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Post by nmchris on Mar 31, 2015 16:43:10 GMT -5
Thanks for the tips Pauls, yes I am saving money right now so I can buy a set of four diamond wheels off eBay. The reason I am changing wheels so often is because the machine I am using only has room for two wheels. The SC grinding wheel and the sanding drum for the SC belts. So after I do the rough shaping and then using the first SC belt (220 grit) I have to turn the machine off and swap belts to continue working. The reason I was worried about grit contamination is because in addition to the drip system for keeping the wheels wet there is also the reservoir that holds water under the wheels. It fills up just to the point where the bottom of the wheels are wet then begins draining. It seems to me that unless I drained the water between each grit it could be a problem because part of the wheel is spinning in that water which has grit from the previous belt in it. I am using the green drop wax that came with my machine. Sometimes it seems to adhere better than others but other times it pops right off before I even get it to the machine. I have never dopped a stone and had it stay on for the entire sanding process, and I usually have to redop it several times while working on the same grit. It seems like a very simple process, I guess maybe it's oils from my hand causing the problem.
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Post by deb193redux on Mar 31, 2015 16:43:53 GMT -5
if you are trying to get flat tops on a wheel it is tricky. you could consider very low domes or possibly a few lower-grit sanding discs to put on the end plate.
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Post by deb193redux on Mar 31, 2015 16:46:42 GMT -5
your machine should also be draining better. with overhead drip, contamination should not be such an issue. water should not be touching the bottom of the wheels.
you could configure with a 100g or 120g plated diamond wheel (inexpensive) and then an expando drum for a series of SiC or diamond belts. The drum should turn true with no wobble.
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Don
Cave Dweller
He wants you too, Malachi.
Member since December 2009
Posts: 2,616
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Post by Don on Mar 31, 2015 16:59:35 GMT -5
I'm surprised the pan doesn't have a drain. I suggest sponging out the water as it builds up. You don't want the water to fill up to the wheels.
As for the SC wheel, stop the water drip prior to stopping the machine so it spins the water out. 10 minutes is probably excessive. Replace the SC wheel with a diamond hard wheel as soon as you are able.
For beginner cabbing, pet wood and opal are not great choices because they tend to be soft, have pits, fractures, etc. I'd find some nice hard agate to practice with. If you don't have any, I'm sure many members here would be happy to send you some.
Use a dop stick; it will help with the shaping and doming. If dop wax isn't doing it for you, get yourself some superglue and an accelerator and glue the cabs onto a wooden dowel or large nail head. Soak the cabs in a jar of acetone overnight to get off the dop stick. After course grinding on the SC wheel, use the SC belt on expando drum to get the flats out and shape a nice smooth dome. let the cab dry periodically and look at it to see what needs more sanding. don't be afraid to use some pressure on the drum and let the belt contour around the dome of the cab. sometimes I will use a "cover coat" of black marker on the surface of the cab so I can see my progress in sanding the dome and removing flats and previous grit scratches.
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Don
Cave Dweller
He wants you too, Malachi.
Member since December 2009
Posts: 2,616
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Post by Don on Mar 31, 2015 17:06:31 GMT -5
As Daniel mentions, polishing flat surfaces on cabbing wheels is difficult, even for us experienced guys. dome the cab, even if it's just a slight dome.
You mention oily hands...yes, dop wax will fail if the stone is not clean and free of all oil residue. soak the preform in acetone or a degreaser and allow to dry prior to dopping with wax or glue.
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nmchris
starting to shine!
Member since January 2015
Posts: 26
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Post by nmchris on Mar 31, 2015 17:19:59 GMT -5
Man that is wild that domes are easier than a flat surface. I guess it makes sense because the wheel is curved. I can certainly agree that it is difficult to do. I took my last batch of cabs out and started back at the 220 grit and sanded the face of all of them trying to get it even and flat. Well it looked better than my first attempt but there are still little uneven spots. They are not noticeable indoors but when I take the stone outside and move it in the sunlight the imperfections really show up. I took another look at my machine, I think that it does drain just before the water gets to the wheels. The way I had the drain hose snaking out caused it to curve up a tiny bit, increasing the amount of water the reservoir holds, which is why it was hitting the wheels. I just assumed that was how it was supposed to work because that little bit of dripping water didn't seem like it was enough water to keep the whole wheel wet. Hey that super glue method sounds great! Once I can actually make a decent cab I will try to get better with the dopping wax. I also wanted to do some really small stones for some projects I was making, it seems like it would be tough to dop a really small stone and super glue may be easier for me. Thank you everyone for the tips, it is much appreciated. Although none of my cabs came out how I wanted I do have some positive news to report, one of the pieces of opal wood I cut had a bore hole from a larvae in it. It was not visible until after I cut the stone but somehow I lucked out and split it right down the middle and got two matching (albeit poorly made) cabs with a sweet bore hole in them!
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Post by pauls on Mar 31, 2015 21:52:02 GMT -5
I am sure you will get there. We all have to start somewhere. The green doping wax should be perfect, I reckon its the easiest to use. I agree with what every one else said about the dome, its very difficult to do a good flat, there are tchniques but its much easier to cut a dome.
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Post by stardiamond on Apr 1, 2015 0:22:34 GMT -5
I gave up on wax a long time ago. I was just using my fingers, but then I started dopping with superglue. I got my first cabbing equipment which was a worn 80 grit diamond, a worn 220 grit diamond, a belt sander that you could spray with water and a leather pad with tin oxide. I paid about $300 for everything and was not happy with my work. I bought a genie and went all diamond and never looked back. A two wheel system will work fine when you do a lot of cabs in stages. The 2 hard wheels and 4 soft wheels using grits similar to what is in a genie. People more skilled than I can get good results with wheels and drums. You can find the four soft and two hard wheels for about $600 on ebay.
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