Question: May one use a manual spice-grinder on Shabbat?
Answer: The Mishnah (Shabbat 73a) teaches us that one of the thirty-nine forbidden works on Shabbat is grinding. Those works forbidden on Shabbat were the works associated with the construction of the Mishkan (Tabernacle). In the Mishkan, herbs and other ingredients were ground in order to produce colors to dye animal hides. It is thus forbidden to grind wheat, barley, or other herbs on Shabbat.
The Rambam (Chapter 8 of Hilchot Shabbat) states: “One who grinds spices on Shabbat is liable (for Shabbat desecration).” Not only is one who grinds food items on Shabbat liable for Shabbat desecration, for even one who grinds other substances, such as one who produces sawdust from trees, has desecrated Shabbat by grinding.
It is therefore quite clear that it is absolutely forbidden to grind any kind of spice on Shabbat. It is likewise forbidden to use a manual grinder not powered by electricity (and is used by turning the device itself or a lever attached to it to grind the spices within it) on Shabbat, for grinding spices on Shabbat is a Torah prohibition.