Learn what to do if a stand-alone grinder hums and has a small vibration, but does not grind.
If your grinder hums and has a small vibration but does not grind, then it is locked up. To resolve this issue, set your grinder to a more coarse setting, then operate it again. You may need to go a very coarse setting to get it going.
Please also be sure to keep track of how many turns you make, or how far you are backing it off. Then, turn halfway to the setting the grinder was at when it was locking up. Then, put in coffee and slowly dial it back down to the proper grinder setting. Always make sure the grinder is running when adjusting to a finer setting.
Do not rush and do adjustments in small increments, or it may lock up again!