What is a "K" chart (profile) of a gear? How is it prepared? Though the Total profile deviation allowed is 16μm, the "K" chart gives a profile deviation of different values at different roll angle. Pl exlain. Thanks
Hi Uday, 'K' charts are graphs generated for the permissible deviations of form and lead errors, for spur and helical gears. These charts are based on the earlier AGMA standards, and do not appear in other standards as DIN, JIS etc. Each gear will have its own k-chart. Due to several shortcomings in this method, the new AGMA standard has not inferred K- chart for lead and profile evaluation. Hope this helps you.
Hello Ramana, Thanks for such a neat information. I have one more question on that. If 'K' chart is not used nowadays, how is the profile deviation and lead deviation explained in the drawing? Thanks.
Gear errors are controlled by 3 items Tooth to tooth error abbreviated TTE Total composite error abbreviated TCE tooth thickness. These parameters are measured by mating your gear with an extremely precise master gear and measuring the center to center distance of the two gears. Now that you have the terms, you can search on line and continue your education.
Hi Erich, Thanks for that. But will those errors be a replacement for 'K' chart? I believe 'K' chart tells me how much can a profile be different from true involute form, which is intentionally done and not considered as an error. Correct me if I am wrong. Thanks.
Uday, The lead and profile deviations given in the drawing usually follow some international gear standards. The gear is inspected for these parameters on an gear-checking instrument, and the output is a graph which reflects the deviations. However, some profile and lead modifications like tip-relief and tooth crowing, will result in a different shaped graph, and the designer usually specifies the limits of these deviations. Now when you combine these two that is, the deviations from a true involute, specified lead
Here is the remaining part... Now when you combine these two, that is, the deviations from a true involute & lead and the design modifications of these two, the result arrived at is the acceptance limits of the deviations against which the gear is inspected.