Greenwatts

LM339 Spur Gear

Cut a piece of threaded rod for the the spur gear aprox. 10cm long. File down one end (8 to 10mm) to match the inside diameter of the spur gear, press the spur gear onto the shaft and epoxy. Note that this need to be a very tight fit to prevent the spur gear from slipping on the shaft. We must raise the spur gear to match the height of the worm gear so we will make a small platform by laminating several small squares of flat ABS together. Once the height is matched add another square piece with a hole drilled to match the diameter of the bottom of the shaft. This will act as a shaft guide and bearing surface so make sure it is loose enough to rotate freely but tight enough so there is no sideways movement. Cement the platform into place making sure the spur gear meshes with the worm gear while the spur gear shaft is perfectly vertical. Be careful not to make the spur gear / worm gear contact to tight or it will bind.