Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[RGB776]

Hello, new to this forum and lapidary. I recently bought a used Covington heavy duty two station grinder and plan on using this unit to bring rough agates to a finished/polished state. The unit came with 8,000 and 14,000 grit diamond wheels. My plan is to buy a 6" 80 grit diamond wheel and keep it on one side of the unit for rough grinding of the agates. On the other side have an expandable drum using 100, 220, 400, 600, 800 and 1000 grit silicon carbide belts. Are all of these belts needed or can a guy skip a grit stage? For polishing I plan on using a felt belt on a separate expanding drum with cerium oxide, can the agate go strait to the polish stage after the 1000 grit belt or should I use the 8000 and 14000 diamond wheels first? Any and all input is greatly appreciated and thank you for your time!

[Slabbercabber]

Assuming the existing wheels are soft matrix, they can be used for polishing.  If they are hard wheels then they are not lapidary.  The 220 can be skipped but it will take longer if you do.  Some stones can go from 1000 to polish, but I always take any stone well beyond that to get that glasslike finish.

[RGB776]

The existing wheels are soft diamond resin wheels. Do you think there would be any advantage in polishing with the felt belt and cerium oxide or would the 14000 diamond wheel give the stone a glasslike finish? Thank you for the information!

[55fossil]

    I would suggest using all the grits and not skipping any, at least for awhile. Every type of agate and jasper can cut and polish a little differently. After you notch up a hundred or so cabochons and flats you will have some idea of what is needed to get a good finish on some stones. Some people do seem to be naturals at making good cabochons but if you read the old discussions you will notice even the best cabber's here are still learning. Skipping steps as a newbie could be an invitation for disaster. You will likely find out soon there is no one answer to how to polish all stones.
   As for the Covington it is a great unit. I have a two wheel variable speed unit with expandable drums on both sides. It is an awesome machine but if you want to produce quality cabochons it takes time and practice. Good luck and welcome to a world full of surprises to come.

[RGB776]

Thank you for your input, I'm sure it will be a learning process. I've read through a lot of the discussions here and seems like there is multiple ways of arriving at the same results with each person's preference on what equipment to use. Just get the bigger scratches out with smaller scratches until it's shiny and you can't see any more scratches.

[Ryaly2dogs]

First off, congrats on your purchase.  I would recommend you purchase a 220 diamond wheel as well, since an 80 grit leaves very deep scratches that you can spend way too long trying to grind these off using SIC wheels.  Also, for stones below a hardness of about 5, I always start with a 220 diamond wheel for the same reasons, and also because an 80 can take you past a preform border before you can whistle dixie (a.k.a. killing flies with a sledge hammer).

Before I went from SIC to diamond, I used 360, 400 and at 600 SIC off an expandable drum and went straight to polish on a bull wheel with variable results, soft stone went OK, agates were challenging.  I now go from 220 hard diamond to 280 and then 600, 1200, and 3000 NOVA (soft diamond) with superior results.  I often do not need to further polish after a 3,000 diamond.  Consider your 8,000 and 14,000 as over and above...they will be great to have, but they may not be needed for many fine polishes.

This is just my opinion here...If you stay with SIC, I think you can skip #800 since you capture it with the 1,000...even the 400 is questionable because as your 220 wears, it starts acting more like a 400 and you always have the 600.  As you said below, you are merely progressively erasing deeper scratches through this process, no need to add steps.  Where I am going with this is with so many belts you might lose the "buzz" of finishing a stone for need of always switching out belts.  Something to keep in mind, because for me the buzz is what keeps the interest!

Enjoy.

[RGB776]

Thank you for the information. Sounds like if I went the expando drum route I'd still have to buy the 1200 and 3000 soft diamond wheels to make it shine. I might just go with all soft diamond wheels after the 2 hard diamond wheels and skip the drums all together. A little more spendy but I don't mind spending more up front to get the results I want. Looks like it would be the same wheel setup as the cab king.

[Slabbercabber]

I use rubber backed diamond belts.  My experience is that they outlast several Nova wheels.  However, I have not tried resurfacing the soft wheels.  If I didn't have a very large stock of belts I would probably try that.

[Ryaly2dogs]

Don't mean to digress (too much) on this thread, but I hadn't heard that about the diamond belt longevity!  If they truly outlast a NOVA, I may need to reconsider as I am in need of a new 600.  About what are you paying per belt?  And do they go over a standard 8 inch expando drum?

thanks.

David.