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TECHNICAL BRIEFS

# Design of a Special-Purpose Hob With Prescribed Value of the Hob-Setting Angle for Machining of Cluster Gear

[+] Author and Article Information

EATON Automotive, Innovation Center, 26201 Northwestern Highway, Southfield, MI 48076stephenpradzevich@eaton.com or radzevich@hotmail.com

The $DG∕K$ approach is based on fundamental results obtained in differential geometry of surfaces, and in kinematics of multiparametric motion of a rigid body in $E3$ space. The interested reader is referred to (2,10) for details of the approach.

The interested reader is referred to (13) for details of the generating surfaces of involute hobs having various orientations of the axis of the screw motion with respect to the auxiliary rack pitch plane.

The numerical example is developed for the $ζh$-hob having design parameters, which are equal to the corresponding design parameters of the FETTE gear hob (see p. 1, DIN 8002A, Cat. No. 2022, Ident. No. 1202055).

The effective total height of the gear hob tooth $hr$ does not include the gap between the gear outside diameter $Dog$ and the root diameter $dfh$ of the hob. The actual value of the effective total height of the gear hob tooth $ht$ can be computed from the formula $ht=Cg∕h−0.5(Dog+dfh)$(11-12).

J. Mech. Des 129(4), 438-444 (May 10, 2006) (7 pages) doi:10.1115/1.2437807 History: Received December 05, 2005; Revised May 10, 2006

## Abstract

This paper aims to develop of a robust analytical approach for computation of the principal design parameters for a special-purpose involute hob for machining of cluster gear. The specific combination of design parameters for a precision hob with particular value of the hob-setting angle is given. This combination of parameters includes (a) the hob outside diameter, (b) the base diameter of the hob, and (c) the required value of the hob-setting angle. The specific combination of these design parameters for the involute hob determined here allows machining of cluster gear with the shortest possible neck width. Numerous computer codes for computation of the design parameters of an involute hob are developed using the commercial software MathCAD-Scientific. Application of the special-purpose hob would allow reduction of size and weight of both the cluster gear itself and the whole gear transmission including housing. The reported results of the research are ready for application in industry.

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## Figures

Figure 1

Cluster gear

Figure 2

Satisfaction and violation of the first necessary condition of proper generation of the gear tooth surface G

Figure 3

Generation of the auxiliary phantom rack R of the involute hob

Figure 4

Impact of the pressure angle ϕnR of the auxiliary rack R on the width of the tooth top land

Figure 5

Generation of the cylindrical machining surface of a hob for hobbing the involute gear

Figure 6

Impact of the hob-setting angle ζh on the top width of the hob tooth (1, 2, 3 corresponds to the hob tooth pointing)

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