10.2 GEARCALC/ page 2


Figure 10.2: GEARCALC - Wizard page 2

10.2.1 Material selection


Figure 10.3: GEARCALC - Material

The material of the gears can be selected from the material database. The strength is dependend of material type, treatment and quality. Material treatment

There are different possibilities for heat treatment: through hardened, nitrided, induction hardened and case hardened materials: Material quality

Material quality strongly influences pitting resistance and bending strength. For high quality material, the following metallurgical variables must be carefully controlled:

There are three basic grades of material: Own input of material data

Using the plus button PIC next to the material list the material values can be entered directly by the user. You have to be careful choosing the values since they are not checked by the software. Important for the calculation are the allowable stress numbers sac{σHlim} and sat{σFlim}. The youngs module is needed for the hertzian stress and the yield point for the static strength. The hardness value is only used for documentation.

10.2.2 Quality according to AGMA 2000/AGMA 2015

The quality for both the pinion and gear can be defined independently. The actual quality achieved is dependent upon the manufacturing process used.

10.2.3 Finishing method

  1. Finish cut:
    Many gears are not shaved or ground. Accuracy and surface roughness of as-cut gear teeth depend on the condition of the cutting machine, the accuracy and rigidity of the fixtures which hold the gear, the quality of the gear blank, and the quality of the cutter. For gears that are cut only, the most accurate are through hardened gears whose teeth are cut after the gear blanks are heat treated. Carburized gears are cut and then heat treated and usually must be finished by grinding to remove the distortion due to the heat treatment. Nitrided and induction hardened gears usually are not ground because they have low distortion due to heat treatment. The shallow case depth of nitrided gears makes grinding risky. Sometimes nitrided gears are shaved or ground before nitriding to obtain good surface finish and accuracy.
  2. Shaving:
    A finishing process which uses a pinion-shaped shaving cutter with hardened steel helical teeth that have radial gashes which act as cutting edges. The shaving cutter is run in tight mesh with the gear to be shaved with the axes of cutter and gear skewed. Axial sliding removes small amounts of material. Shaving is frequently used as a final finishing operation on through hardened gears, and sometimes as a finishing operation before nitriding. It can be applied to both external and internal, spur and helical gears. Shaving can produce profile modification (e.g. tip and root relief) and lengthwise (helix) modification. Shaved gears are usually cut with a protuberance cutter followed by shaving of the tooth flanks only.
  3. Grinding:
    Gear teeth may be ground by either the form-grinding or generating-grinding method. Either method is capable of producing the highest accuracies of any finishing method. Both spur and helical gears can be ground. Most grinders finish only external gears; some can grind internal gears. Some gear grinders can produce profile and helix modification. Grinding is used where high accuracy is required and most often used for finishing carburized gears to remove the distortions due to heat treatment. The strongest gear teeth are cut with a protuberance cutter and ground on the tooth flanks only, leaving the root fillets unground.

Comparison of tooth finishing methods:
Gear ToothAccuracy Surface Brinell
Finishing Quality RoughnessHardness
Method No. Qn μin (rms) Limit HB

Milling < 6 64-125 360
Shaping 6-10 32-125 360
Hobbing 7-11 30-80 360
Shaving 10-13 10-40 360
Grinding 11-15 10-40 None

The finishing method has an influence on the selected tool addendum according to the GEARCALC setting (see 11.1.5).