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Post by sheltie on Oct 1, 2012 11:29:55 GMT -5
This is the next step (of MANY) in my continuing effort to try to learn the hobby.
Now that I've gotten the slabbing and degreasing (deoiling) part down, how do I get a high polish on the slabs? My vibrating lap doesn't appear to be the solution and I'm considering a wet polisher. Regardless of what I get, how do I actually hold the slab in place to polish it? Why can't I use the leather wheel on my cabbing machine - or can I?
I Googled wet polisher and there are many listed. I'm not sure what the difference is between the BD one commonly talked about ($575) but these appear to be about the same, just considerably less expensive. What about Dremel attachments? Are there any that might work?
Lots of questions, just trying to learn so that maybe I can help someone in the future who has the same questions.
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Post by Hard Rock Cafe on Oct 1, 2012 14:02:27 GMT -5
The large flat areas of the slab are difficult to do on wheels, although Bobby1 long ago posted a method using worn SiC belts dry. Your vibrating lap should be able to do it; that's what they're designed to do. It may be a question of technique.
You may be able to do it on the leather disc, but it will depend on the shape of the disc and whether you can make contact with a large flat area.
Does that make sense?
Chuck
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Post by deb193redux on Oct 1, 2012 14:38:06 GMT -5
Are you weighting the slabs on the vibe-lap? What is the main deficiency with the slabs you polish on your vibe-lap?
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Post by johnjsgems on Oct 1, 2012 17:08:33 GMT -5
Yes, vibe laps will work but BD wet polisher is much faster. On my demo box I use with mine I have a piece of warehouse matting on the bottom of the pan. Slabs and flat rocks stay in place pretty well on the mat. Before the demo box I used a $5 "mud pan" from Home Depot. It is a black plastic tub found in the section where concrete/plaster/etc. is and usually in garden center. I drilled a drain hole and set it on a piece of plywood on either saw horses or a shop mate stand. Biggest problem with the wet polisher is you tend to get a little wet unless you are extremely careful so it isn't a cold weather unit. I do have customers that use their units in the basement in the Winter using a bucket of warm water and a submersible pump. A vinyl apron is a good thing to have.
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Post by sheltie on Oct 1, 2012 18:52:43 GMT -5
The large flat areas of the slab are difficult to do on wheels, although Bobby1 long ago posted a method using worn SiC belts dry. Your vibrating lap should be able to do it; that's what they're designed to do. It may be a question of technique. You may be able to do it on the leather disc, but it will depend on the shape of the disc and whether you can make contact with a large flat area. Does that make sense? It does make sense but we just haven't gotten the "formula" on how to make them shine yet. We have yet to try the leather disc but plan to try it with smaller slabs. Chuck
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Post by sheltie on Oct 1, 2012 18:54:58 GMT -5
Are you weighting the slabs on the vibe-lap? What is the main deficiency with the slabs you polish on your vibe-lap? No I haven't weighed the slabs, only the weights. Help me understand the ratio between the weight of the slab and the weight of the weight and how to use that in preparing whatever grit mixtures and the time for each process that I need to use. My problem, or deficiency, is that I can't get the high shine that I've like to get.
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Post by deb193redux on Oct 1, 2012 18:58:53 GMT -5
I don't understand "weight of weight"
folks use small lead-shot bean bags or even metal discs that grip the slab (like a slab grabber) and work both as a bumper and a slab weight.
without weights 1/4" thick slabs generally do not polish well.
make sure you blade is giving you an almost 1200g smooth cut. that helps a lot with subsequent polishing.
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spicer m
spending too much on rocks
Member since October 2008
Posts: 337
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Post by spicer m on Oct 1, 2012 23:07:00 GMT -5
I bought the BD wet polisher from John at JS Gems a couple years ago and love it. It is very fast. I put sheet rock screws around the outside of the slab to keep them in place, (just below the top of slab) I use a old picnic table and screw a bunch of them down to do at one time. I do mine outside and put a 6" high plywood gaurd up to keep water off me.
I go trough all the stages of discs and do one side of 6 to 8 slabs in about 45 min. I have a 16" rotating cast iron lap that uses SC grit and a 16" covington vib lap that pretty much just sit in the in the corner now. As John said You do get a little wet, also have to keep water flow down so You don't suck it in to motor windings. Some times I put a plastic bag around motor air inlet to make sure no water gets in. Have not had any problem with overheating. When I looked into buying a wet polisher I found out that the cheaper ones where haveing a problem with O-Rings failing in water coupling and destroying the motor. That was Why I went with The Barcada Diamond. Give John at JS GEM a call "Update" just read Your post dated the 28th (small inside area to work in. Do What John said with a inclosed tub, could screw slabs down to plywood and set it tub. Mike
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Post by sheltie on Oct 2, 2012 7:40:24 GMT -5
I don't understand "weight of weight" folks use small lead-shot bean bags or even metal discs that grip the slab (like a slab grabber) and work both as a bumper and a slab weight. without weights 1/4" thick slabs generally do not polish well. make sure you blade is giving you an almost 1200g smooth cut. that helps a lot with subsequent polishing. Weight of weight refers to the weight of the weights I use. Plural, not singular. I use various weights that I get from my local service station. My saw blade is brand, spanking new, BD, and when a slab is cut it looks perfect with the oil still on it. It's when the oil is gone and I have to polish it that I'm not happy with the results of the vibrating lap.
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Post by deb193redux on Oct 2, 2012 8:41:43 GMT -5
it sounds like you are putting weight on top of the slabs. I am not clear because of the seemingly conflicting statements about weights. I asked about weighting and you responded NO about weighing, and then spoke of ratios.
If the slab is only lightly pressed on the grit/polish plate and bounces even slightly with the vibrations, the grinding/polishing action is very slow. You want enough weight to be about the equivalent of you pressing down with light force on the slab - about the force you would use if you were rubbing the slab on a sheet of sandpaper.
If I use a MK225 blade I get about a 180g cut face that shows slight frosting when dry. When using an MK 303 blade on hard stone, I can get a cut fact that looks like somewhere between 100g and 1200g. Often areas will have a dull burnish/sheen even before any further polishing.
When I used my old 10in vib-lab, I got glass-like finish on faced rocks real easy. For slabs that only weighed a few ounces, I had to get weight on top of them to make them closer to a pound before they benefited a lot from polishing. I would grind any nubs and sometimes put a slight bevel on edges before lapping. I ran in 1200g or tripoly until the slabs gave a uniform flash when moved under a light source. Then I used AO polish on a piece of wool-like pad. The results were as good as AO polish in a tumbler. But the whole setup was messy and needed a lot of supervision because it dried out so often.
Are you running a fine grit before going to polish?
The weights often shook free. Getting the weight securely on the slab was a pain. Silicone sealant helped.
I have heard stories of some rock where any oil residue in the rock will prevent high-gloss polish. I can't report on this 1st hand however.
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Post by sheltie on Oct 2, 2012 12:51:43 GMT -5
Obviously, I'm having a hard time explaining. Let me try this. We use a plastic container, about 4" in diameter, inside of that are the weights (lead). On the bottom of the plastic we have glued a thin plexiglass disk and then we attach the slabs with special (why I don't know) double sided tape.
For the larger slabs (which I prefer), I use my 16" blade. For the smaller ones we also use the MK 303. but the latter is mostly used prior to cabbing.
We use two grits, then a fine grit and then a polish (you may note that this isn't "my" job, it's my wifes. I handle the big saw). We used to have occasional problem with a slab coming loose, but not recently.
I hope this clears things up.
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Post by deb193redux on Oct 2, 2012 17:13:32 GMT -5
Yes, clear.
It sounds like you have sufficient weight. ... and you are using enough grits to sand before polish.(it may be best to grind any nubs and ski the coarsest grit. it may be roughing up the face if you have a good blade.)
all the steps seem correct? you should get decent results.
is a slurry forming? is it drying out? how long at each grit, how long in polish? could you polish pad have any contamination issues?
are you getting a satin shine? ... a high satin?, ... glass-like but with dull areas?
if you use the lap to polish the face of a heavier cut nodule, do you get good results? (I ask this to sort out issues of drying and contamination and grits from issues of weight)
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Post by johnjsgems on Oct 2, 2012 17:48:37 GMT -5
Daniel makes a good point. If large rocks come out well you need more weight on your slabs. You can even use larger rocks on the slabs. When I first got my Lortone lap I tried to do slabs without any weights. They just bounced on the surface doing nothing. The bevel around edges is a good thing too. A good grade (like .3 micron or finer) of aluminum or most lappers swear tin oxide is best polish. If you are using coarser aluminum oxide like the 3-4 micron tumbling polish compounds that may be part of your problem.
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Post by sheltie on Oct 2, 2012 18:07:48 GMT -5
Yes, clear. It sounds like you have sufficient weight. ... and you are using enough grits to sand before polish.(it may be best to grind any nubs and ski the coarsest grit. it may be roughing up the face if you have a good blade.) all the steps seem correct? you should get decent results. is a slurry forming? is it drying out? how long at each grit, how long in polish? could you polish pad have any contamination issues? are you getting a satin shine? ... a high satin?, ... glass-like but with dull areas? if you use the lap to polish the face of a heavier cut nodule, do you get good results? (I ask this to sort out issues of drying and contamination and grits from issues of weight) Yes, a slurry forms. No it isn't drying out. Generally two to four hours with each grit, About two hours on the polish pads and it's doubtful either of the three we have are contaminated, although I will recheck. I would categorize the final product as a fairly high satin shine rather than a glossy one. We haven't tried any nodules as yet, concentrating on slabs.
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jspencer
freely admits to licking rocks
Member since March 2011
Posts: 929
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Post by jspencer on Oct 2, 2012 18:14:41 GMT -5
I do all of mine in my modified vibrating tumbler from Harbor Freight. I replaced the motor with a Dayton 3" dia. 1/40 hp 3300 rpm motor. I used a counter clockwise rotation and added a 5" fan that blows back onto the motor to keep it running very cool. I cut down the factory weight a little also. I have done some 1/8" thick in there with no problem.
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Post by deb193redux on Oct 2, 2012 18:22:47 GMT -5
I say get a 4" solid coconut geode and cut it in half. try to polish. or take a double fist sized pice of rough and cut in half.
if you can polish those, it is an issue of weight. if you can't then you have to look for some other factor.
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