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 Post subject: Using master lap and grit compound
PostPosted: Thu Apr 10, 2014 3:55 am 
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This may sound like a dumb question….. :?
But here goes

Using an old style master lap :
How do you keep the larger grit on the Lap???


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 Post subject: Re: Using master lap and grit compound
PostPosted: Thu Apr 10, 2014 1:10 pm 
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Welcome

No question is stupid or dumb! Its how we find things out.

I am pretty sure that a master lap is only to hold toppers and and other thin cutting and/or pollishing films to keep them flat.

Also this should probably be in the lapidary area.


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 Post subject: Re: Using master lap and grit compound
PostPosted: Thu Apr 10, 2014 4:48 pm 
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Thanks
I will look there


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 Post subject: Re: Using master lap and grit compound
PostPosted: Thu Apr 10, 2014 6:31 pm 
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what he said^^^^^^^^^


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 Post subject: Re: Using master lap and grit compound
PostPosted: Sun Apr 13, 2014 1:56 pm 
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This is an even dumber question, are you talking loose grit? I assuem so... in that case the answer is you do not, on a master lap.


You may be confusing terms. ere a master lap is a plain lap with no cutting action at all. It is used under other things like Topping laps. These are thin laps that cost less and will not support themselves (hence the need for the master lap under them).

The other type of lap that takes grit is a chargeable lap. They come in many materials (copper to tin (like a BATT lap) or even wax). They are charged based on the type of material.

Larger grits in these tend to be pressed in using something as simple as the edge of a ball bearing. They do make special tools for them.

Many of the softer laps can also be charged by taking a piece of CZ or carborundum and using it to press the material into the lap after you put on a slurry.


If you search "charge lap" you weill find several threads here, and on u tube.


There are some things like the gearloose diastick that simplify this process.


Good lock and welcome to the forum.


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 Post subject: Re: Using master lap and grit compound
PostPosted: Mon Apr 14, 2014 3:26 am 
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Yes I guess your right I am talking about charging a lap with other than 50,000 diamond grit polish.
I am using diamond toppers, but I have some 1200 grit I would possibly like to use. My Dad Left me quite a lot of lapidary odds and ends. I am not sure what the gran size is but I do have some sapphire powder etc. sorry its late and I am rambling .....

Thanks ElvinM


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 Post subject: Re: Using master lap and grit compound
PostPosted: Tue Apr 15, 2014 2:44 am 
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Waht are you using for the lap material? Some materials are no good for laps as the grit does not imbed in them. Traditionally copper laps are used for cutting grits but Batt laps can be charged with cutting grits too. just remember that any charged laps is easily contaminated and care must be taken when charging them. if one is charging more then one lap at a time make sure that every thing is clean between laps. it only takes on speck...

I have a number of copper laps that I use for cutting grits for 3k and below I use Batt. To charge my copper laps I do the following. I clean the lap with wd40 and then wash it over with liquid soap. I put the laps on the machine and then dampen the lap with mineral oil and smear a thin layer over it with my finger. I then use a tooth pick to sprinkle a little diamond on the lap in several places and spread it out with my finger. under low speed I grind the diamond powder into the lap with an agate slice. I swish the mixture left on the lap around with my finger and then flip the machine in reverse and press it in again. If the mix on the lap dries out drip on a little more oil. I then repeat the process in forward and reverse again. If its not imbed by the then it won't ever be I be. I wipe the lap over with toilet paper to remove all the gunk. I then wash the lap again with liquid soap and running water. I find that more diamond becomes imbedded with several light charges as opposed to one heavy charge.

If using diamond powder is not to your taste you can make a paste using 10-15 ct diamond powder in 20 ml handcream with a drop or two of silicone oil and load it into a 20 ml syringe.

The diamond sticks that Gearloose sells are also supposed to be excellent but I have never use one of these.

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 Post subject: Re: Using master lap and grit compound
PostPosted: Wed Apr 16, 2014 1:55 am 
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Location: Vancouver, Canada
I have recently become a fan of 600 and 1200 on copper for roughing, and I have a RedWing+5 for harder stones charged with 3k outer/50k inner.

My copper lap is one of Jon's custom ETP laps I got a couple of years ago. Not sure what sort of variation there is between copper laps from other manufacturers so I can only tell you my experience.

I tried to charge the copper initially with loose 600 grit and SnakeOil, trying to bed the diamond with a large chunk of corundum generously sold to me as "star sapphire." For several minutes I pushed a large amount of oily diamond around the lap to find very little embedding - so eventually I gave up in frustration and put the lap away. I then thought about ordering a bearing to roll the diamond into the lap surface, but instead settled on getting one of Jon's Water-based DIASTIKs.

After lightly misting the lap while spinning about 60 rpm so it was damp (not dripping, just damp) I applied about 1/16th inch of the stick to the lap. I then took the same corundum chunk and started working it back and forth across the lap, increasing the speed to 150-200 rpm. This time the diamond started to set immediately and I could feel the corundum dragging as it was being ground away. I continued this for about 2 minutes, then rinsed the lap and took a look. It was frosted and had a reasonable amount of diamond embedded, so I started cutting my rough. I had to repeat the process once more for this particular stone and perhaps 6 times total over the next 2-3 stones before it reached its current heavily-loaded and happy state.

(I believe the problem with the loose bort is one of the oil being a lubricant - allowing the diamond to slip and slide over the lap instead of catch and embed. I also believe it was acting as a release agent so in the cases where diamond was trying to embed, the oil prevented the diamond from bonding to the copper and it would pop out. Greater minds than mine will probably know if I'm spouting poop or not. :) )

For the other side of this lap I did the same with one of Jon's 1200 grit water DIASTIKs. Same process, except I noticed it took longer for the diamond to embed. For the 1200 it took perhaps 4-5 minutes before I was sure that I wasn't just pushing diamond around the surface. This side has had 5 full charges and is now heavily-loaded and cuts almost as fast as the 600, but with a much smoother finish. I am using the 1200 side now almost exclusively for roughing - actually it's fine and accurate enough for me to make good meets before moving to 3k prepolish, and prepolish now take seconds as I am only fine-tuning the meets instead of grinding away the rough 600 surface to make the meets.

For the RedWing+5, I used standard 3k DIASTIK with SnakeOil on the outer and 60k DIASTIK with SnakeOil on the BA5T center. Both charges were embedded using a small synthetic spinel boule, working it back and forth across the band in question for perhaps 2 minutes total before using it.

Same goes for charging the outer band of the BATTWing products. BATT is softer than copper and the 3k diamond embeds much faster than on the copper RedWing+5.

I have had no issues with bort flying off the lap causing contamination. My precautions are to wear surgical gloves when charging (and cutting most of the time - I hate black fingernails) and to flood the cutting laps with water and spin them dry before lifting them off the machine. I also have a very high slash wall - 4" tall silicon rubber sheet that I stand up in the splash pan when roughing with water but removed for oil-based prepolish and polishing.

I tried to make a video of this process a couple weeks ago and keep meaning to edit and upload it somewhere... but that has kind of fallen by the wayside. Perhaps it's time for me to try to get it done over the long weekend.

Hope this helps.

-Allan

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 Post subject: Re: Using master lap and grit compound
PostPosted: Wed Apr 16, 2014 3:36 am 
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Thanks Allan
This helps a great deal ...
I am also looking up the posts on charging laps
I see I have a lot to learn. I guess I have been falling in the right direction, I have cut some garnet that look real good and some aquamarine.

Thanks

ElvinM


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