The last time I looked at emery sand, it was unbelievably expensive, so I started using kitty litter. It's baked clay that is crushed into little pieces. It is abrasive, so sharpens pins and needles, and it is inexpensive. I make weighted bases for the pincushions I sew by using ceramic tiles (either the square or rectangle) as the base. I sew a fabric covering that the tile slips into from either the same or contrasting fabric. The covering has a piece of velcro sewn down the center and the open end is slipstitched closed. Then, I make a pincushion that has the other half of the velcro sewn on it. You can remove the pincushion from the base, but it will not slip off.