Gear Wearing
Gear Wearing
(OP)
Hello,
I am very new with gears, but here is my problem:
I have been presented with the task of determining exactly when a pinion/gear set fail. I figured the best way to do this was measure the nominal backlash and backlash after the components have been used. I have come across a rule of thumb for backlash requirements:
min backlash = 0.03 / diametral pitch
avg backlash = 0.04 / diametral pitch
max backlash = 0.05 / diametral pitch
Do these equations hold true?
I have various spur, worm, rack and pinion, and bevel gears that were sent in for wear testing. The measurements were returned and the circular tooth thickness was measured at the pitch diameter. Is there a way I can approximate backlash with nominal and worn circular tooth thickness? I have looked through various PDFs online as well as the Machinery Handbook and have had a very hard time. Any helpful information that I could find mostly related to spur gears.
Overall, any information as to how to determine when gears "fail" (even if the machine using the gears is working) would be greatly appreciated. Thanks in advance!
I am very new with gears, but here is my problem:
I have been presented with the task of determining exactly when a pinion/gear set fail. I figured the best way to do this was measure the nominal backlash and backlash after the components have been used. I have come across a rule of thumb for backlash requirements:
min backlash = 0.03 / diametral pitch
avg backlash = 0.04 / diametral pitch
max backlash = 0.05 / diametral pitch
Do these equations hold true?
I have various spur, worm, rack and pinion, and bevel gears that were sent in for wear testing. The measurements were returned and the circular tooth thickness was measured at the pitch diameter. Is there a way I can approximate backlash with nominal and worn circular tooth thickness? I have looked through various PDFs online as well as the Machinery Handbook and have had a very hard time. Any helpful information that I could find mostly related to spur gears.
Overall, any information as to how to determine when gears "fail" (even if the machine using the gears is working) would be greatly appreciated. Thanks in advance!





RE: Gear Wearing
Does whoever presented you with the task know what failure mode for which they want the test run?
Ted
RE: Gear Wearing
My method was to avoid stress beyond 1/2 yield. Fatigue is the consideration.
RE: Gear Wearing
RE: Gear Wearing
RE: Gear Wearing
What is the typical failure mode for the gearing it it's application?
Transmission error, vibration, tooth breakage, spalling, micropitting, etc?
David
RE: Gear Wearing
You might look at something similar.
If you wait until backlash changes, wear has progressed where most gear designers would say its too late.
RE: Gear Wearing
It is very uncommon for gearsets that are properly designed, manufactured, and maintained to experience "wear" as you describe it. Specifically, a loss of material from the tooth working surfaces. In most cases, a properly designed gearset would not operate in contact conditions that produced the fretting/galling action which results in material removal from the tooth flank surfaces.
As geesamand notes, the more typical failure modes for gear teeth are surface contact fatigue spalls and/or bending fatigue failures.
Hope that helps.
Terry