### Helix/Lead Tab

Use the Helix/Lead tab to specify the parameters for the measurement and evaluation of the helix/lead. Helix/lead measurement is optional; if you do not want to measure the helix/lead, clear the Measure option.

Define Gear dialog box – Helix/Lead tab for cylinder gear

Measure: When you select this check box, the helix/lead will be measured during the measurement process based on the parameters defined on the Helix/Lead tab.

Click this button to set the values for Start Z (near lower face), End Z (near upper face), and Diameter in the Measurement area based on the gear parameters. It will also set the values for Start of Evaluation Range (lower face) and End of Evaluation Range (upper face) in the Evaluation area based on the gear parameters.

Measurement Area

Teeth List to be measured: The box to the right of the list specifies the tooth numbers for which the helix/lead will be measured based on the Number of teeth value on the Parameters tab. The list defines for how many teeth the helix/lead will be measured. By default, the profile will be measured on four teeth. The following options are available in the list:

- All: Measures all of the teeth. When you select this option, the teeth range automatically appears in the box, and you cannot change the value.

- Custom: Measures only the teeth that you type in the box. Separate the teeth with commas. For example: 1,8,14,20. An out-of-range error symbol will flash to the right of the box if the value that you enter in the box is out of range based on the Number of teeth value on the Parameters tab.

- 1, 2, 4, and 8: Enables PC-DMIS Gear to automatically calculate the teeth to measure. The teeth automatically appear in the box, and you cannot change the value.

Helices on left or right flank: This list lets you specify the flank to measure. Available options are: Left, Right, and Both. To determine the left and right flank of a tooth:

- For an external gear, imagine you are standing on the center of the gear and looking forward at the gear's tooth. The left flank is on the left side of the tooth and the right flank is on the right side of the tooth.

- For an internal gear, imagine you are standing in the center of the hole and are looking at a space between two teeth. The left flank is on the left side of that space and the right flank is on the right side.

Start Z (near lower face): This value is the Z coordinate location where the helix/lead scan begins. The helix/lead scans always start at the bottom and move upward.

End Z (near upper face): This value is the Z coordinate location where the helix/lead scan ends. The helix/lead scans always start at the bottom and move upward.

Diameter: This value defines the position at which helix/lead scans are measured. This value can be defined as Diameter, Roll Length, or Roll Angle. You can select the option for the Type of input for definition of involute position/region parameter in "Step 3: Modify PC-DMIS Gear Settings". The name of this option depends on the selection in step 3.

Evaluation Area

Start of Evaluation Range (lower face): This Z coordinate value represents where on the helix/lead scan you want to begin the evaluation. You should use a value slightly larger than the helix/lead Start Z value.

End of Evaluation Range (upper face): This Z coordinate value represents where on the helix/lead scan you want to end the evaluation. You should use a value slightly smaller than the helix/lead End Z value.

Magnification of Deviations: This value is a percentage that all errors will be magnified by for display in the evaluation.

Magnification of Range (%): This value is a percentage that all errors will be magnified by for display in the evaluation. If you type a zero, PC-DMIS Gear calculates the value internally.

Tolerance of Helix Angle Deviation (fHβ): Provides the allowable distance between two design helices which intersect the mean helix at the extremities of the evaluation range. See the appropriate gear standard for a definition of this value.

Tolerance of Total Helix Deviation (Fβ): Provides the allowable distance between two design helices which enclose the actual helix over the evaluation range. See the appropriate gear standard for a definition of this value.

Tolerance of Helix Form Deviation (ffβ): Provides the allowable distance between the two design helices parallel to the mean helix which enclose the actual helix over the evaluation range. See the appropriate gear standard for a definition of this value.

Tolerance of Lead Error (Vψ): See the appropriate standard for a definition of this value. This value is for the AGMA gear standard only.

Evaluate Crowning: This value determines if crowning should be evaluated. If it is checked, then crowning will be evaluated. If it is not checked, then crowning will not be evaluated.

Minimum Crowning: See the appropriate standard for a definition of this value.

Maximum Crowning: See the appropriate standard for a definition of this value.

When you select this button, PC-DMIS Gear calculates the tolerances for the helix/lead evaluations based on the standard and Grade specified on the Parameters tab.

Report Setting

Draw K-Chart: This check box determines whether or not the Tolerance K-Chart appears in the report. For a definition of the K-Chart, consult the gear standard.

Draw Grid Line: This check box determines whether or not grid lines are displayed in the report. Grid lines act as a ruler of sorts, indicating in the report how large the deviation is.

Define K-Chart: This button lets you define the parameters of the K-Chart for profile and helix/lead. See the "Define K-Chart for Helix/Lead" topic.