The geometry of the bevel gear is quite complicated to describe mathematically, and much of the overall surface topology of the tooth flank is dependent on the machine settings and cutting method employed. AGMA 929-A06 — Calculation of Bevel Gear Top Land and Guidance on Cutter Edge Radius — lays out a practical approach for predicting the approximate top-land thicknesses at certain points of interest — regardless of the exact machine settings that will generate the tooth form. The points of interest that AGMA 929-A06 address consist of toe, mean, heel, and point of involute lengthwise curvature. The following method expands upon the concepts described in AGMA 929-A06 to allow the user to calculate not only the top-land thickness, but the more general case as well, i.e. — normal tooth thickness anywhere along the face and profile of the bevel gear tooth. This method does not rely on any additional machine settings; only basic geometry of the cutter, blank, and teeth are required to calculate fairly accurate tooth thicknesses. The tooth thicknesses are then transformed into a point cloud describing both the convex and concave flanks in a global, Cartesian coordinate system. These points can be utilized in any modern computer-aided design software package to assist in the generation of a 3D solid model; all pertinent tooth macrogeometry can be closely simulated using this technique. A case study will be presented evaluating the accuracy of the point cloud data compared to a physical part.

NASA is now 3-D-printing spare parts up at the ISS (International Space Station). And in zero-gravity environments. And some of these parts are small gears and actuators, for starters. Every indication is that the list of power transmission-type parts to be converted will soon grow.

How should we consider random helix angle errors fHβ and housing machining errors when calculating KHβ? What is a reasonable approach?

Have you ever stood on a beach at the edge of the water and felt the grains of sand dissolve from under your feet as the water recedes? No matter how hard you plant your feet or grip your toes, you can’t hold on to the sand. It just flows away right from under you. In many ways that sand is like the knowledge and experience of our graying manufacturing workforce. It seems inevitable that much of that knowledge is being washed away.

This issue, GT Extras brings you "Heat Treat and Induction Hardening of Industrial Gears," a treasure trove of heat treating related technical articles and a call for help in preparation for AGMA's 100th anniversary.

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