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Program: The Installation of Bevel Gears


Part 3 - Methods for checking the Contact Pattern

Contact Pattern

The true purpose behind the parameters of mounting distance, matched teeth and backlash is to ensure that the teeth are contacting each other properly. By following the manufacturer’s specified variables during installation, the tooth contact should be ideal as manufactured.

However, it may be necessary to verify the contact pattern of the gears once they are installed in a gearbox. The process of checking and interpreting the contact pattern will be described in this section.

To begin, you’ll need a few materials - including a brush, marking compound, a piece of cardboard, standard clear adhesive tape and cotton swabs or toothpicks.

For the brush, this can be a small paint brush - available from any hardware store. However, you’ll want to trim the bristles to about 1/2" in length. When trimming the brush, it’s a good idea to make the cut with a slight angle or bevel.

As for the marking compound, Arrow uses a special orange colored marking compound paste during the inspection process. However, this is usually only available in bulk so it’s not a good option for the occasional user. As an alternative to this marking compound, you can use a substance called Prussian Blue. Prussian Blue is typically used for the layout of dies to check for contact. Prussian Blue can be obtained from a number of industrial supply distributors such as McMaster-Carr - or at many automotive parts stores. It may also be referred to as high spot marking paste.