Good morning. I`m looking for some more advise about polishing slabs o a 18" flat lap, regular lap, Not vibratory. Bought one used and cheap and reconditioned it with a 3 phase motor and a VFD, which allow for slowing down to any RPM from the motor`s original 1350 RPM. We tried using it with loose grit but it`s too messy and have to wash out each time when changing grit. Anyway, bought a set of 18" diamond disks (80, 220, 325, 600, 1200 and 3000) and set up a drip system. Am used to working with smaller pieces on a 6 wheeled Genie and a 8" flat lap also, using same grits as above. After a 4 hour session of trying to lap several slabs of different materials, it`s been frustrating and results have not been good. Main problems are not getting the scratches out enough between different grits and not getting a shiny finish, even after 3000. Anyway, here are some specific questions:
1.) What RPM do you recommend for this case? Same RPM for all disks of all grits? Same RPM for all stones?
2.) Is it OK on a larger lap like this to try to lap several different stones on the same disk in the same session? (Yesterday, we were lapping 4 to 6 " slabs of crystal quartz, lapis, serafinite, obsidian and even tried to polish the faces of some hard cut in half geodes.) We assumed that this was OK and that we were not contaminating as there was a a good drip on the disks. We cut and polish all kinds of stones everyday on a Genie and never have contamination problems. But maybe on a 18" flat lap it is different.
3.) I was thinking also that maybe we should be more thoroughly washing the slabs and other materials between the different disks, to avoid any possible contaminations.
Any advise would be helpful. I have been excited to put this machine to use after time and $ to set it up. But so far its been quite frustrating. Thanks.