How to Restore Dull Gear Appearance: Cleaning Tips and Consequences

Question:

After being stored for an extended period, a double helical gear set was sent for cleaning. Normally, new gears have a polished finish resembling freshly machined metal. However, upon return, the gear set had a dull gray appearance, likely cleaned with a corn cob blast or similar media that did not polish the metal. Have you encountered this issue before? Will there be any negative consequences if the gear set is installed correctly after being cleaned in this way? Share your insights.

Top Replies

Is there a specific level of cleanliness required for the parts used in the gear application process? If the parts are not polished (such as fresh cut metal), should it be anticipated that the gear will produce more metal debris or dust compared to before?

I am concerned about how this will impact tooth wear patterns and potential wear problems in areas where teeth mesh with a blast finish. Will this cause higher gear mesh vibration compared to a machined surface in a short amount of time? I am unsure of what to expect and whether this approach is considered a good, better, or best practice.

Avoid grit blasting the gears when polishing metal, as it can be similar to continuously peeling off skin from a wound - it only exacerbates the issue. I remember instances where we replaced gears by washing away the old grease, cleaning the bearing seats with sandpaper, oiling the components, and putting them back into operation.

Update: The gear that was sent out for cleaning was found to be very rusty, with a significant amount of pitting likely caused by the rust. A representative from a gear manufacturing and repair center will be visiting the site today to provide recommendations. The gear that was initially considered for replacement will remain in place for now. Additionally, the gear representative will offer best practices for addressing this damage. The gear had been stored improperly for approximately 25 years, as the current company owner has only been in place for 6 years and did not implement climate control measures. It has been suggested to review storage practices for all rotating equipment to prevent similar issues.

Is it feasible to fix damaged gears through weld overlay on pitted areas and reshaping them to their original smoothness, or should a replacement be considered instead? Additionally, which AGMA specification governs the repair of gears?

Yes, I've come across this situation before. The change in your gear set's appearance is likely due to the abrasive cleaning method used, as you've suspected. While this might alter its aesthetic appeal, it shouldn't pose any operational issues as long as the gears were installed properly and no significant material was removed during cleaning. Do keep an eye on them, though, and make sure to frequently lubricate to prevent any chance of excessive wear and tear due to potential surface roughness induced by the blasting process.

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Frequently Asked Questions (FAQ)

FAQ: 1. Why did the gear set have a dull gray appearance after being cleaned?

Answer: The gear set likely had a dull appearance because it was cleaned with a media such as corn cob blast that did not polish the metal surface.

FAQ: 2. Is it common for gear sets to lose their polished finish after cleaning?

Answer: It can happen when certain cleaning methods, like using corn cob blast or similar media, are used that do not result in a polished finish on the metal surface.

FAQ: 3. Are there any negative consequences of installing a gear set with a dull appearance?

Answer: As long as the gear set is installed correctly, there should not be any significant negative consequences to its performance even if it has a dull appearance.

FAQ: 4. How can I restore the polished appearance of a gear set that has become dull after cleaning?

Answer: To restore the polished appearance, you may need to use a different cleaning method or consider polishing the metal surface manually.

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