herb
spending too much on rocks
Member since November 2011
Posts: 445
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Post by herb on Sept 4, 2013 12:43:33 GMT -5
Hi everyone, I recently picked up this flat lap that has a home build frame with a Covington flat lap: I don't know much about it and was wondering if someone could give me some pointers on how to use it. The top plate, looks to have diamond grit embedded in its surface. The back is inscribed "GEM-70" Here is a close up: Under that is a rubber mat: And under that, is a smooth disk: Am I correct in assuming that the top plate is a 70 grit plate? In using this, I assume I would first rough grind on the 70 grit plate using just water and then for the next step remove the top plate and then charge the smooth plate with finer grit slurrys maybe something like 200, 400, 600 grit (cleaning between each of course). Is that the gist of how one uses a flat lap, or am I missing something? Any additional hints you might have would be appreciated!
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dellis326
off to a rocking start
Member since January 2012
Posts: 10
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Post by dellis326 on Sept 4, 2013 22:31:42 GMT -5
You don't use grit on this machine. You'll need to get more removable pads that have different grits. Start with coarse and work your way to the finer grades.
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herb
spending too much on rocks
Member since November 2011
Posts: 445
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Post by herb on Sept 6, 2013 17:07:38 GMT -5
You don't use grit on this machine. You'll need to get more removable pads that have different grits. Start with coarse and work your way to the finer grades. I should have mentioned that the lap plate is 16 inches in diameter. I'm not sure there are supposed to be separate plates for each grit. I just looked on the covington site and looked at the instructions they have for their 16" single speed lap. They don't mention anything about a diamond coated plate like I showed in the first picture, but they do give directions on mixing up pastes of various grits to go through the polishing stages.
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dellis326
off to a rocking start
Member since January 2012
Posts: 10
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Post by dellis326 on Sept 6, 2013 23:13:36 GMT -5
Yes, separate plates for each grit.
That isn't the same machine shown as on the Covington site. The hub on yours is designed to hold disks down against the plate. The hub on the laps for grit are different. These big grit laps have a V shaped channel with a drip can/tank or other water source for the grit to drip down on the plate. A paste or non-renewing slurry will be thrown off of it and you'll end up sliding your stones against the steel without cutting.
If your machine has a water supply without the trough to hold and supply loose grit then it is intended to be used with disks.
Loose grit is much cheaper and often faster then disks but you need to seriously clean the whole machine very time you change grits. I mean like take it outside and hose it off and then hose it some more. Even one or two stray pieces of 120 grit in the mix when using your 300 or 400 grit will leave a pretty noticeable scratch on your piece.
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