Every morning since April 2018, I would grind one scoop of beans at the largest setting, 8, for my French Press cup of mocha. It was quick, it was easy, in about 25 to 30 revolutions of the handle I had my coffee grounds ready to go. Cleaning was fairly easy but the bean oils were difficult to remove inside the top hopper.A while ago, I’m not certain as to when this began, I felt a grinding sensation rotating the hand crank when I was done grinding the beans and there were no beans left to grind. I didn’t pay any attention to it. If I had known this symptom was the precursor to failure I would have stopped and solve the problem. Hint! Hint!If you are using a Handground Precision Manual Coffee Grinder, heed my warning: if you rotate the handle with no beans in the hopper and you’re feeling and hearing a rhythmic thumping, grinding sensation and sound, the internal gears are out of synchronization. The gears are not meshing the way they did originally because the gear set screws are loose. Do not rotate the crank anymore. The top cap assembly needs replacement. If your Handground Precision Manual Coffee Grinder is still under warranty, send it in for repair/replacement.Otherwise, you will have to disassemble the top cap assembly.WARNING THIS IS NOT TO BE ATTEMPTED IF YOU ARE THE LEAST BIT SENSITIVE TO THE SIGHT OF BLOOD OR INTERNAL WORKING MECHANISM! Or if you lack mechanical aptitude, the tools or the time.This will take some specialized tools, Phillips head screw driver of a particularly small size and a 1 mm Allen wrench, hex head wrench. Be aware that there may be spacing washers or shims on the shafts of all these drive gears. If they are present, they will need to be returned to the same position. The three screws holding the top cap together are Phillips head, use a precise sized Phillips driver or you will round off the Phillips screws and then you have a paperweight. Carefully remove the screws and place them in a secure container, my preference is a Titan Tools 11061 Mini Magnetic Parts Tray.After you have disassembled the top cap assembly, you will see six more Phillips head screws securing the cover plate of the gearbox. Carefully remove those six screws, they’re small, put them in the same secure container. In figure one you will see the exposed gears under the cover. In this same image you’ll also see the set screw securing the gear to the drive shaft. The sets crew is the problem, it has become loose. The set screw is a 2.5 mm screw and I think it will require a 1 mm hex drive Allen tool to remove it. Do so very carefully this is an extremely small screw. Place the screw in the secured container. You can now pull the crank shaft out and remove the gear. Now the vertical driveshaft is exposed and can be removed. Remove that set screw as well, I don’t need to tell you what to do with that set screw, right?Figure three is the underside of the gearbox cover, and you can see a lot of debris and pieces of metal. Clean out the interior of the gearbox carefully, you want it absolutely clean.The two gears appear to be interchangeable, however, if they are not you must return them to the same original position in the gearbox. Take whatever steps are necessary to ensure this happens. Use a magnifying glass to closely evaluate the gears if they appeared undamaged they can be used again.You will want to have some thread locking fluid before you reinstall the set screws. Using an appropriate solvent, follow the cleaning instructions accompanying the thread locking fluid.Clean the gears very thoroughly removing any oils and debris. Be sure to clean the inside of the threads for the set screws as well as the set screws, according to the instructions for the thread locking fluid. Allow the cleaning solvent to dry thoroughly.Now you’re ready to reassemble. Being mindful to return any spacer washers to the original position, place the gear on the vertical shaft aligning the hole for the set screw with the flat surface on the shaft, following the instructions of the thread locking fluid apply the fluid, it will take very little on a screw this size. I put the fluid on a toothpick and then applied a very small amount on the screw threads while the set screw was on the Allen wrench. Insert the set screw back into the hole and tighten down snugly. Wipe off any excess thread Locking fluid. Replace the vertical drive shaft with secured gear, into the hole of the top cap, checking to be sure it rotates freely. Slide the hand crankshaft into the top cap aligning the appropriate gear (and any washer spacers) with the shaft as you insert the shaft into the gear. Align the screw whole with a flat surface on the shaft. Repeat the procedure for the previous screw. Using the toothpick technique, place a small amount of light silicone oil on the gears. (WD-40 is a Water Dispersant, not a lubricating oil. That is what WD stands for) Replace the gearbox cover, screw in place, do not over tighten the screws, it is easy to do. Somebody told me that. Reassemble the head and you’re back in business.In my effort to accomplish what you have just done, I discovered the gears had been severely damaged. They would still work but for how long, I do not know. My caution about having a magnetic storage place for your screws is the result of losing one of the set screws. They both fell from the table onto the floor. Amazingly I found one but the other did not reappear. That’s how I found out what size they are when I bought a new one cost: 30¢ I have been able to reassemble the drive, and it does work but it still has that vibration feeling and sound I described originally. No idea how much longer this will last but that’s OK, I purchased a replacement thinking my Handground Precision Manual Coffee Grinder was done for. I’ll do a review on the new one after I’m done with this review.