how often to change grit

Jeg, I run a UV-18 vibe and my stones or unpolished cabs are 99% preshaped on the flat lap or grinder wheel before they are run through the stages. I use 2 or 3 days for each stage and then clean thoroughly before moving to the next step. Step one 100/220 might be run twice to make sure all deep scratches are removed before going to the next step. I am retired so cleanout is determined after visually checking dry material under the loupe before moving on- I take samples. Please remember that my rough is a different in starting shape.

You change grit when it's consumed / broken down. This also varies according to how your barrel is loaded. This also assumes were talking about stage 1-3. Final polish has it's own rules. Stage 1 is also more variable dependant based on other conditions.


There's endless discussion on this topic, but a lot of opinions on the are just plain false.

My 3lb barrels go through two heaping tablespoons of 120-500 in about 3 days max. A far cry from a lot of people saying you need to tumble for weeks. My seemingly short times are due to using more media in the barrels and fewer rocks to polish. You can prove this yourself with large ceramic or 3/4" river gravel. Both of which make exellent filler media. Fill your barrel 2/3 full with either, and two tablesppons of 120/220, and check it every day to see how long it takes for the grit to totally be convertd to grey goo with no grit left. Will take about 72 hours.

Take that same barrel and fill it 3/4 full of 1.5 " rocks and your times will increase dramatically. Much less surface area to grind against and less fluid tumbling rotation. So, it all depends on how you fill your barrel.

I can final polish a 3" rock in 3 days if I use 1/4 ceramic and nothing else. Again, if that barrel was full of 1.5" rocks the times go up a factor of at least 3-4X. Just physics.