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Worm Gear Pair Geometry Parameters

A worm gear pair is defined by a standardised theoretical basic rack profile and 7 independent geometric quantities:

1 Module mx or mn
2 Number of starts of worm z1
3 Number of teeth of wheel z2
4 One of the following quantities da1, d1, q, γ
5 Center distance a
6 Worm length b1
7 Face width wheel b2

Input with following dialog box:

Geometry Dialog Box

Input of a parameter or change of a parameter, followed by pressing the Tab key, triggers a calculation with actual input: the user can see the effect of latest input.

Note that for the worm there is a choice for input of one independent quantity out of the following:

Tip diameter worm da1
Reference diameter worm d1
Diameter quotient q
Lead angle γ

Input of a quantity as independent and press the Tab key to calculate the others as dependent quantities. The lead angle γ can be entered expressed in sexagesimal or in decimal degrees. Input of center distance a is optional, on no entry the center distance is considered as dependent quantity. Alternatively, the profile shift coefficient for wormwheel x2 can be entered, the center distance is then considered as dependent quantity. The application calculates the minimum and maximum applicable center distances, while keeping the profile shift coefficients in range. The minimum and maximum profile shift coefficients in function of the flank form are displayed in the dialog box.

Still required input: face width at root of wormwheel b2 and crown width of wormwheel bc2 and some other design dimensions for the wormwheel crown. This is all done as shown in the following dialog box:

Wormwheel Geometry Dialog Box

Mean normal backlash and backlash tolerance

The application allows the backlash to be apportioned over the worm with a scale from 0 to 100 %. Selection is done by means of a trackbar. The rest percentage is then apportioned to the wormwheel. Results of geometry calculation in table form looks like:

Wormwheel Geometry Output

Click here on Calculation Report Geometry to open it with your browser in a blank page.

Go to next web page for worm gear forces.