rlt
off to a rocking start
Member since September 2008
Posts: 9
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Post by rlt on Jun 10, 2011 16:59:18 GMT -5
I'am looking for suggestions on how to add weight to geodes on a 20" flat lap. I think something like a lead donut would would help. It polishes fine except for unpolished streaks. Thank You... RLT
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snuffy
Cave Dweller
Member since May 2009
Posts: 4,319
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Post by snuffy on Jun 10, 2011 17:24:36 GMT -5
What I have found on my 20 inch lap is that when you get the unpolished streaks,it means the surface of the geode has not been ground enough to be completely flat to polish the entire surface.Saw marks,just even a small deviance in the cut will show up when polished if not completely ground flat.Icould usually tell by letting dry and looking at the surface at an angle towards the light.Thats my take on it,interested to hear others. On rereading your post,I guess I didnt first get it,you want to add weight to get it to grind better,right? snuffy
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Post by Jack, lapidaryrough on Jun 10, 2011 17:45:55 GMT -5
Rit
1/2 Lb. our higher is fine for weight. Though if you are doing geodes, Fell the cavity with soap.
This well keep the hollow Geode clean. What i do is grate scape bars of soap up and hand pack the Geode.
What i do on my Laps ( 20" & two 27" ) i allows face sand the material before it goes to the laps. I only use 220 Grit on the rough grind. when the material grind to what i like. i per-polish on a expandable drum.
Loose grit Lapping, seems to look frosted if you run through the 600 grit lapping phase and go to the felt polish pad. when you jump from glued paper grind - 320 - 600 - then to dry sanding with worn 600 belt dry - with rock dust for per- polish. our a heavy paste, with very little water added. Then to the polish pad. I use Lamb - 1/4 carpet. Cerium oxide.
Now i pass on some ideas other well tell ya. i skip some phase`s and do it My -Way. As Elders of past have done.
Oh ya the plate on the Hp -Laps are $600.00 with two side for lapping. under the polish plate theirs a grooved plate.
Why i only use 220 Grit rough grind. and pre sand the material. !!
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Jasper-hound
starting to spend too much on rocks
Member since June 2010
Posts: 208
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Post by Jasper-hound on Jun 12, 2011 8:28:27 GMT -5
I use 60/90 rough with slabs weighted by adhering other face-cut rocks on top of them, using water glass, available at pharmacy. Water glass will later dissolve when soaked in warm water, but difficult to remove from pores or pits. Use a metal scribe to make cross hatched marks on the work piece. When all the marks are abraded away, the piece is ready for the next finest grit.
I have an HP lap and have indeed worn out one side of the grooved plate, so you might want to take the other fellow's advice. However, I feel that the machine is made to use, and when I wear out both grooved sides I will just bite the bullet and buy another rather than doing any presanding, which would be difficult to get perfectly flat, in my opinion. I do, however, grind off any protruding nibs from sawing.
craig
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Post by johnjsgems on Jun 12, 2011 8:47:17 GMT -5
Most laps are aggressive enough to use 220 to start (or 120/220) Like vibe tumblers the coarser grits really do more harm than good. Some lap plates are thick enough to have regrooved when needed.
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Post by jakesrocks on Jun 12, 2011 9:35:33 GMT -5
It helps to grind a slight bevel about 1/16" in from the outside edge of your Geode or nodule. This allows grit to get under the piece you're lapping.
Craig, No need to buy a new lap when the plate wears out on your HP. The Diamond Pacific vibro laps are the old HP laps with a screen guard added around the bottom. Lap plates and suspension parts are still the old HP parts. Don
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Post by johnjsgems on Jun 13, 2011 12:16:50 GMT -5
Another reason for the edge bevel Don advised is it helps prevent edges chipping off and scratching the faces during finer stages/polish.
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Post by tandl on Jun 13, 2011 12:29:52 GMT -5
I use baggies with pea gravel in them, then taped so they dont wear from the friction , as fast , to add weight to smaller specimens . Make several and only use the same ones for different grits .i have had the problem on some materials, where the egde polishes, but not the center. Think the bevel idea will work for that . But does the bevel polish on the lap?
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
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Post by quartz on Jun 15, 2011 19:09:57 GMT -5
I just finished some t-egg halves in the 3 1/2-6 lb. range on our newly acquired HP 27' lap. Added a pound+ of triangular fishing weights to each, got a really good polish, but the surface is textured like looking at the ocean from an airplane. This our third vib. lap, supposed to be better than the older ones, but same problem. Is this pretty much inherent with vibes, or am I not finishing properly? My wife says they are fine, I'm too picky. I want glass smooth.Open for suggestions, thanks. Larry
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Post by johnjsgems on Jun 15, 2011 19:15:41 GMT -5
Are you going through the grit stages? I've heard vibe lap users swear it makes a difference to use graded grit (220, 400, and 600). Let the finest grit break down before washing and going to polish. It is the grit that makes the surface smooth. The grit for all practical purposes only makes the prepared surface shiny.
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Post by jakesrocks on Jun 15, 2011 19:31:59 GMT -5
You may have to finish the polish on a felt wheel. Some just refuse to polish in the middle, no matter how long you let them run on the polish pad. Don
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Post by Jack, lapidaryrough on Jun 15, 2011 20:40:00 GMT -5
I just finished some t-egg halves in the 3 1/2-6 lb. range on our newly acquired HP 27' lap. Added a pound+ of triangular fishing weights to each, got a really good polish, but the surface is textured like looking at the ocean from an airplane. This our third vib. lap, supposed to be better than the older ones, but same problem. Is this pretty much inherent with vibes, or am I not finishing properly? My wife says they are fine, I'm too picky. I want glass smooth.Open for suggestions, thanks. Larry Loose grit runs wont polish, need face sand with glued grit pads, like bull wheel or disk, use worn 600 belts or new 1200,, our your way! i have tried to go from loose grit 220 to pad, after the grit had broken down to about 1200 fine. you can l tell by the shine, When held flat to the glare of a lite. how well the grit has broken down. I use a arbor with a 3 x 8 expandable wheel. Before i go to a 24" Wool rotary pad. i run it at 265 RPM. with cerium oxide Less water may help too, I use a spray bottle, some times a IV - 1 Drip - every 3 seconds Always fell the pan full with Rocks & bumper guards. As Don said Bevel the edges of the Material, about 45 Degrees at 1/16th of inch. Dons, wright grit to move under and it cuts down on chips that cause cork screw scratches. Learn the hard way, just keep dialing in, and ask a lot of question. We all well Dazzle ye with B-S. i well count on it........ Jack
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
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Post by quartz on Jun 15, 2011 23:13:10 GMT -5
Thanks to all for the quick responses. It isn't the polish I'm unhappy about, it's the texture of the surface. Always attend the shows in Rickreal and Hillsboro [OR], and I can pick out the same texture on a lot of lapped slabs, in varying degrees. The goal here is not just flat and shiny, but smooth too. Different description of condition: an auto painter would call it "orange peel", in minature. One big t-egg and a large piece of pet. wood we put on to fill the table came out better than the rest, but still not happy to picky old me. Jack, I've been dazzled w/BS for lots of years, learned a bunch after sifting it. Thanks.
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Post by Jack, lapidaryrough on Jun 15, 2011 23:57:23 GMT -5
Thanks to all for the quick responses. It isn't the polish I'm unhappy about, it's the texture of the surface. Always attend the shows in Rickreal and Hillsboro [OR], and I can pick out the same texture on a lot of lapped slabs, in varying degrees. The goal here is not just flat and shiny, but smooth too. Different description of condition: an auto painter would call it "orange peel", in minature. One big t-egg and a large piece of pet. wood we put on to fill the table came out better than the rest, but still not happy to picky old me. Jack, I've been dazzled w/BS for lots of years, learned a bunch after sifting it. Thanks. i know all the dealers in the Rickreal show and the WAMS Club, Their Bull wheel addicts, 99.5% do their work on expandable drums. Flat your after, use a plate glass sheet with 220 grit the 600 grit the a 1200 belt. then onto cerium pad. To the public the dealers, fast grind their material knowing the general public don`t know. Why i only buy rough, at the show. the old dealers do it the wright way though the cost is higher and they ask the price for there work. On a 48" rotary wheel with 220 grit. then on to bull wheel worn 600 grit. & 1200 worn doing a pre-polish with rock dust from the 1200 grit. At this point to the plate glass lapping with 3000 grit. then the cerium oxide. Bottom line you know what you want, the public don`t. so fast and cheap for sale. Jack
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Jasper-hound
starting to spend too much on rocks
Member since June 2010
Posts: 208
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Post by Jasper-hound on Jun 24, 2011 23:54:31 GMT -5
My vibro lap finishes smooth as glass. One thing I do for specimen slabs is just cut them much thicker--3/8 to 1/2 inch. That seems to give them enough weight to polish great.
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Post by connrock on Jun 25, 2011 11:22:58 GMT -5
The only way I know of to get that glass like finish you're after is to do the very same as you would in rock tumbling! The first and maybe the most important thing is the "rough stage". If the rock or in this case the flat surface(s) are not PERFECTLY flat you WILL NOT get a good finish on them.
"Hatched marks" was mentioned but I'd like to elaborate on them a bit. Take a Magic Marker and make what looks like a cross word puzzle on the surface to be roughed in. Run this for about 2-3 minutes,wash it off and inspect it. This should give you a pretty good idea of weather this surface is truly ready to be and or how long it will take to get roughed in on your flat lap. As in tumbling,some rocks are ready for the next stage before others so you may want to start to save those that are not ready for another rough and continue with those that are ready.Your call here.
After you've run you roughing to a point where you "think' the slabs,etc are ready for the next stage,,,wash them off,dry them and make that cross word puzzle again,,,making SURE that you mark the VERY edges of the flat surface(s).
Inspect the surface(s) VERY carefully under good lighting and look at them closely.If you see ANY resemblance of a mark DO NOT continue to the next stage. (different color magic markers for different colored surfaces,,,don't use black on black,etc)
After I don't see any marks I do the slab,etc for about another 30 minutes just in case.
If you follow this throughout the entire process I think you will have much better results.
Something bout weighing down you slabs,etc,,,,,,,,
It is VERY important to weigh down the pieces evenly.In other words do not weigh down one side more then the other or the center more then the outer areas and vise versa..
If the outer area is weighted more then the center,,,the piece will become concave and the center will not polish properly and vise versa! Finding the center of gravity on any given piece helps to position weight too!
I've seen a LOT of different ways to weigh down different types of pieces and about the only one I really like is the water glass that was mentioned here previously.
Cross contamination will kill you as well(sorry for rambling here)!
I'm somewhat of a perfectionist too so I know what you're going through and also what you are trying to achieve and it's NOT easy! LOL
connrock
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quartz
Cave Dweller
breakin' rocks in the hot sun
Member since February 2010
Posts: 3,341
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Post by quartz on Jun 25, 2011 20:28:27 GMT -5
Thanks again for the commentary, I'll get this thing , someday. One thing I've noticed is the rocks appear to be "jumping" a bit as they circulate the table, this I think is likely causing the texture. I've got no instructions with the machine, so I'm sorta flying by the seat of my pants. Will the finish likely improve if I fiddle with the weight, maybe cut the amplitude down a bit? I know the subject mtl. is flat before leaving 220, and very careful to see 600 is properly finished. Being careful to keep my weight additions as balanced as possible. I have the tools to measure changes, and return to original if necessary.
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Post by Jack, lapidaryrough on Jun 25, 2011 21:27:48 GMT -5
Level, And Balanced
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Post by connrock on Jun 26, 2011 6:40:09 GMT -5
I would say that if the rocks are small and are jumping around that you need more weight but if they're heavy enough then you should probably move the counter balance to ease up the vibration.
I don't know if all vibe lap mfg's are vague with the instructions they send but I have a Covington and they might as well have kept the instructions they send and just enclose a note saying,,"Good luck fella"!
There's a fine point between the correct amount of water and too much water and keeping the correct amount of water consistently is another story. A lamp shade or something similar helps evaporation and a water drip will help as well but to me the vibe flat lap is the worse piece of lapidary equipment I have ever used.
connrock
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Post by Jack, lapidaryrough on Jun 26, 2011 8:21:32 GMT -5
RIT,
I to did`t read the instruction of the 20" An 27" highland-parks either .
I did find that a good saw cut is most important, face sand some saw marks out. if your auto feed our blade leave deep saw marks. "Your not ready to use the Lap. "
Lap are for facing the stones and roughing them for Bull Wheel or disk sanding through the next few stages.
Loose grit grinding from the lap wont polish well.
even if you done the 600 grit run.
I have my way, I only use 220 Grit. and i face sand and, grind the edges of all rocks. and face sand on 120 grit disk. My saw cuts are very smooth. most large Laps in the 36" - 48", is only 220 grit
Then i run the material through the 3x8 expandable wheel using 320 - 600, then a worn out 600 and the dust from light water on wheel. like a light mud. to speed pre polish up.
Finish with glued grit pads, our drums.
Laps are only a short cut. from not doing a lot of work by hand.!!!
A 27" lap well do about 28 ct. of 3" - 5" heels. myself i prefer material in the 1.5 Lb. range or higher.
Finish polish on Cerium oxide on a 24" lamb wool rotary Lap. RPM 265.
Jack
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