Gear Tech Tips

Technical Information For The Gear Industry

This Edition is Sponsored by: Jos. Koepfer & Söhne GmbH

Tech Tips Edition #3

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Involute Error: Diagnosis & Prevention

Based upon the analytical inspection of the Profile of your gear tooth, you have discovered a wavy Involute Error. What are some of the steps you can take to correct this problem?

Chart 1

First, note that this example (Chart 1) is a symmetrical error between the left and right flank of the gear tooth. Unfortunately, most inspection charts will not be as "neat and tidy" as this one, but will probably contain several problems that will overlay each other and therefore will make your diagnosis more difficult.

For this error you should check the following items:

1.) Cutter mounting -

a. Axial and radial runout of the hob should be checked using a dial indicator on the hubs and face of hob while the hob arbor assembly is mounted in the machine.

b. If runout is found, check for cause such as contamination of mounting surfaces and / or bent hob arbor.

2.) Hob sharpening error -

a. Cutter may have been sharpened with runout.

b. Inspect cutter for gash spacing.

c. Substitute with correctly sharpened tool.

3.) Cutter spindle -

a. Inspect cutter spindle for axial and radial runout.

4.) Cutter arbor end support -

a. Using a dial indicator, check the cutter arbor assembly with and without the end support.

5.) Work spindle -

a. Inspect work spindle for axial and radial runout.

b. Inspect index drive for excessive backlash.

By checking the above items, the cause of the Involute Error(s) should be found.

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