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LynxSphinx
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« on: June 06, 2012, 04:48:12 pm » |
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I do not have a flat lap and am looking for other options to making the back of my rough cabs flat. When I cut rough on my little slab saw I can get a flat back but, when I am turning a rough nugget or small chunk of rough I am having to make it flat the best I can on my wheels. This works for small rough but gets tougher for bigger stuff.
Should I get an angle grinder and use that? Is there hard disks I can mount on a polishing head that make it a flat lap of sorts? Open to the advice of the experienced here on the forum, Thanks a bunch Ed
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Eddie
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lithicbeads
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« Reply #1 on: June 06, 2012, 05:28:04 pm » |
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Removing a lot of material from a big specimen is always difficult An angle grinder is a poor solution. For things that are not larger than 4 or 5 inches and all you want to get off are saw grooves an old way works well. Plate glass is a good grinding platform for using loose grit on. You put the glass on a towel or piece of carpet on a well supported surface , wet the glass and sprinkle some 60-90 grit fairly evenly on the glass and start grinding in a circular motion , all over the glass . It is extremely important to use the glass surface evenly so as not to cup it. As the grit breaks down add more grit and water as needed but eventually the slurry on the glass will have to be washed off. If you think you have achieved what you need from that grit clean everything thoroughly and go to a finer grit , If not repeat. No slurry , grit or rock dust should ever in any amount go into your plumbing system. That is an absolute. I have removed saw marks from geodes almost 2 feet across in this manner and then went through the grits until I could polish with an angle grinder. the investment is low and I enjoyed it as well.
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catmandewe
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« Reply #2 on: June 06, 2012, 10:25:45 pm » |
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You can add screw on ends to your wheels that take sandpaper and are flat and will work as a flat lap.
If you know what size threads and if it is left or right hand I can look and see if I have the one you need left. I bought a big box of them and still have a few left.
Tony
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Marc's Lapidary
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« Reply #3 on: June 06, 2012, 11:19:35 pm » |
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Before I got a flat lap I would put a pice of 80 grit wet sandpaper on a flat surface (I used a scrap of laminate counter top) and I would turn the stone in a figure 8 pattern so the sandpaper cuts in every direction.
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Rockoteer
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« Reply #4 on: June 07, 2012, 09:42:58 am » |
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I also use the screw on ends on my cabbing/trim saw. They work quite well.
TOG
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-Gary
Of all the things I've lost..I miss my mind the most.
Whether you think you can, or you think you can't, you're probably right.
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LynxSphinx
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« Reply #5 on: June 07, 2012, 08:07:38 pm » |
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That's what I figuered was the best bet, use a screw on polishing head and glue on sanding disks,
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Eddie
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mirkaba
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« Reply #6 on: June 07, 2012, 08:27:23 pm » |
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Get an inexpensive tile saw. I bought a Workforce at Home Depot 5 or 6 years ago for about 80.00 and just wore out my first blade. I have shaped a lot of rock with it. The blade was really course and when it finally gave up the ghost I had worn the swage off the right side of the blade. It was still cutting but wanted to cut in circles. For a cheap diamond saw it has done a heck of a lot of work including cutting slabs from smaller rocks and even cut a bunch of tile!! You can make a good flat back but it will still need to be smoothed out on your wheels. Whatever you do .....Good Luck!
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Bob
Gathering dust in Montana.
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3rdRockFromTheFun
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« Reply #7 on: June 07, 2012, 08:55:35 pm » |
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Removing a lot of material from a big specimen is always difficult An angle grinder is a poor solution. For things that are not larger than 4 or 5 inches and all you want to get off are saw grooves an old way works well. Plate glass is a good grinding platform for using loose grit on. You put the glass on a towel or piece of carpet on a well supported surface , wet the glass and sprinkle some 60-90 grit fairly evenly on the glass and start grinding in a circular motion , all over the glass . It is extremely important to use the glass surface evenly so as not to cup it. As the grit breaks down add more grit and water as needed but eventually the slurry on the glass will have to be washed off. If you think you have achieved what you need from that grit clean everything thoroughly and go to a finer grit , If not repeat. No slurry , grit or rock dust should ever in any amount go into your plumbing system. That is an absolute. I have removed saw marks from geodes almost 2 feet across in this manner and then went through the grits until I could polish with an angle grinder. the investment is low and I enjoyed it as well.
I use this method for many things - including making large beveled stones (anti-river rocks  ) and it works really well with heavier grits. Past 600 I can't get a rock to do anything but stick to the glass - the slurry creates enough suction that I can't move anything smoothly. Anyway, courser grits not only work well but FAST - much faster than I would have thought anyway. And, as messy as it sounds it beats sandpaper (in my book) because I never get that errant clump of grit that breaks free of the paper and cuts a nice swath style scratch and I go through expensive sandpaper quicker than I go through the equiv amount of grit (based on $ per mm of grind anyway). While we're here - Frank - any way to get past that 600 grit problem I mentioned (it actually starts doing this right at 600) with the suction or do you just have to move to something else (wheel, disc, paper etc)? |
-frank-  |
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lithicbeads
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« Reply #8 on: June 07, 2012, 09:23:47 pm » |
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I think that traditionally 600 was it. I've seen very expensive ( in those days) very old , over 100 years old agates done in Idar and they had the same look that a lot of the old pieces done on glass here in the 60's had .These had a great polish but little or no prepolish , an odd look. For cab backs 600 for a bit then polish should work as the surface area is not much of a problem , essentially you are cheating a bit but it often works very well.
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3rdRockFromTheFun
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« Reply #9 on: June 08, 2012, 10:54:34 am » |
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Well, good to know it's not just me at least - thanks Frank!
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-frank- |
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mirkaba
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Another option.............I have screw on laps for both ends of my Grinder. I put velcro on the left hand side. The hook part is adhered to the lap. I have a large variety of sanding and polishing pads and discs to which there is affixed the loop side of the velcro. There are hard discs from 60 diamond to 50,000 diamond paste on Crystal pads, Silicon carbide discs and a set of 5 inch diamond impregnated polymer pads. Pretty handy and a lot of quick change options...........Bob
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Bob
Gathering dust in Montana.
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LynxSphinx
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When you say screw on laps you mean screw on polishing heads right? Istead of putting foam or neoprean backing and adding felt or what have you with feathering adheasive you just glue on silicon carbide discs to the polishing heads/screw on laps?
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Eddie
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mirkaba
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Yes end laps or polishing plates. I just put velcro on one of them. Self adhesive plus spray on adhesive and the Velcro hasn't come off. Then put some loop side Velcro on whatever pad, disc or lap you want to use.
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Bob
Gathering dust in Montana.
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LynxSphinx
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Cool thanks I will give it a try.
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Eddie
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