Abstract: The invention relates to a method for producing essentially rotationally symmetrical, undercut contours on workpieces (13) that can for example be produced by forging or casting, said workpieces having at least one sub-section (14) to be machined with an essentially symmetrical initial contour. The workpiece (13) is braced by the end that is not to be machined in a recess (11) and when in said recess (11) the sub-section (14) of the workpiece that is to be machined is placed against a tool (12). The tool (12) rotates with a constant or variable speed in relation to the sub-section (14) of the workpiece (13) that is to be machined. An undercut contour is thus produced on the sub-section (14) of the workpiece (13) by machining under the axial pressure.

Abstract: The present invention provides a self cleaning humming bird feeder equipped to protectively store sugared nectar and contaminated feed tank from insect infestation. The feeder including a feeding cup jacketed within a contaminated feed trap emptying onto a contaminated feed holding tank, a feed reservoir and a pump for pumping nectar to the feeding cup. Cleansing of the feed cup may be accomplished by pumping and overflowing excess sugared nectar into the feed cup causing it to spill over with contaminates onto the contaminated feed trap.