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Author Topic: Help needed with new polishing process - Flat lap  (Read 465 times)

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jaslade

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Help needed with new polishing process - Flat lap
« on: June 26, 2020, 03:44:15 PM »

Hello,

[First time post]

I hand cut and polish mostly 2"-4" quartz [some turquoise, onyx etc] and have used an 8" Ameritool flat lap for years. I have no issues at all with the machine, but I am looking to speed up my process and better my final polish results. The issue I have always dealt with is the seemingly with the 600/1200 grit pads they supply.. as well as the polishing pad [which i use either tin or aluminum oxide]. It seems like no mater what I do in the 600/1200 range, the final polish always reveals a very noticeable scratch/streak pattern from sanding. I then have to go back and forth until it gets where I need it. I am looking to eliminate this back and forth and work with better plates.

I don't have an issue with the 80/180 diamond plates [cheap i'm sure] or the 325 'pad', but can anyone recommend a more pro system for the stages above that? I have been looking at cystalite diamond plates [600/1200] any experience? [is the price just for the brand?] what about copper plates with diamond compound.. one for 600, one for 1200, one for final polish [seems expensive]? can I skip the polishing pad all together with copper? And what experience does anyone have with Phenolic plates?

Thanks much for any time you can spare on this.. I do appreciate it!
Jamie





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Felicia

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Re: Help needed with new polishing process - Flat lap
« Reply #1 on: June 26, 2020, 04:48:37 PM »

I use a similar system. When using the 600, how do you check for scratches. I often use a jeweler's loupe here as leftover scratches tend to show up later. Also
use it on the 1200 to find those leftover scratches. Another point, cleaning between grits. Check to your pads, I have had  a bit of grit a time or two over the years, scrubbed with soap and a brush. Okay, you're probably doing all this, but it's what I've got. Haven't used used copper or phenolic. I find plates, do you mean the bonded metal ones with grit? Much more agressive than the equivalent pad and use a 360 metal after 180 metal, then go to a 325 pad to get those scratches out before the 600 pad. Hope this helps, it's my 2 cents worth. 😺
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jaslade

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Re: Help needed with new polishing process - Flat lap
« Reply #2 on: June 26, 2020, 05:02:39 PM »

I use a similar system. When using the 600, how do you check for scratches. I often use a jeweler's loupe here as leftover scratches tend to show up later. Also
use it on the 1200 to find those leftover scratches. Another point, cleaning between grits. Check to your pads, I have had  a bit of grit a time or two over the years, scrubbed with soap and a brush. Okay, you're probably doing all this, but it's what I've got. Haven't used used copper or phenolic. I find plates, do you mean the bonded metal ones with grit? Much more agressive than the equivalent pad and use a 360 metal after 180 metal, then go to a 325 pad to get those scratches out before the 600 pad. Hope this helps, it's my 2 cents worth. 😺

Thanks Felicia, I appreciate the input. Yeah, I am looking to leave the pads all together above 325.. I find they are too unpredictable and wear too easily. And even though I cut by hand, they don't offer enough precision [if that makes sense]. Washing is definitely a must, ha.. that can get you into trouble quick. As far as bonded plates, no.. I am mostly leaning towards solid metal with compounds [though I think the crystalite ones are bonded.. not sure]. I want to upgrade to the highest possible quality so that replacing and fighting tools is less frequent. Thanks again!
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Felicia

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Re: Help needed with new polishing process - Flat lap
« Reply #3 on: June 26, 2020, 06:36:20 PM »

Yes. I got the 360 metal to take wear off my 325 pads as I use those the fastest, it helped. Just seems like that's the way it will be, but getting the 360 helped a lot. At close to $27 a pad I need to make them last. Good luck.
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lithicbeads

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Re: Help needed with new polishing process - Flat lap
« Reply #4 on: June 27, 2020, 06:28:40 PM »

I suspect you are not using the steel plates properly. A dead hard lap has no drape, it does not deform in any meaningful way when you grind a rock on it. However pads do have drape as they bend to some extent to the pressure from the rock. Pads without a rubber backing pad still drape and do not cut the stone evenly as the draping causes the leading edge of the stone to sand to a greater degree while bridging over the center of the stone. A stone that comes to the sanding stage in a relatively flat state will make sanding a chore wasteful of the sanding pad. The solution is to make sure that you do not grin the stone flat on the hard disc but give it some degree of curvature which with manipulation assure that the entire surface of the stone is the leading edge. If you are curving the crown of the stone and still have problems you need to use a pad with no rubber back.Any pad can be made to be more aggressive by just giving it a light spritz of water then sanding until it is virtually dry. This is the exact method we use with all our jade. As pads wear dress them with a small 600 grit diamond ball bit and rinse thoroughly. There is more diamond there it is just under the pads matrix surface. I use pads until they have bare white spots that threaten to tear you just use them spritzed to dry when very worn. To save money on pads you can use silicon carbide discs that are used for the Richardson sander. I drill through the discs that I use the sic pads on and just use a washer under the screw nut to hold them on. They flatten under the torque of the machine however the edges can cut your fingers. A 100 grit sic is virtually useless for sanding unless very well worn it is too aggressive. I start at 220 and go to a worn 600 . A well worn 600 sic belt was considered gold back before diamond pads and wheels and still does a nice job. Go back two grits when finishing the stone on the diamond pads after the 600 worn sic. The " California polish " , a term used 40 to 50 years ago and earlier alluded to scratches remaining on a stone that otherwise was finished properly. In the day of diamond this fault is very fixable with some imagination.
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Stonemon

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Re: Help needed with new polishing process - Flat lap
« Reply #5 on: June 28, 2020, 07:47:11 AM »

Welcome to the forum Jamie!
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Bill
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