Should you shut down if a zerk won’t take grease? What happens if a bearing is so greasy it attracts dirt? Would it be better to not grease than put too much grease in certain bearings? If you replace a sealed bearing, how do you grease it the first time?
Fred Whitford, director of Purdue University Extension Pesticide Programs, determined that if you can’t answer these four questions correctly, you could wind up making costly repairs. He spearheaded a new Extension publication to answer these questions and explore the differences between various types of grease. Choosing and Applying Lubricating Grease: Using Science, Test Results, and Experience is now available as PPP-145.
Here are the answers to those four questions:
Grease fittings. Consider this true story: An employee couldn’t get a grease zerk supplying grease to a trip mechanism to take grease back when people plowed. He told his boss, and the boss told him to go plow anyway. Midmorning, he felt a tug, looked back and saw a plow bottom lying behind the plow. The plow share hit a huge underground rock, the mechanism didn’t trip, and the plow bottom stem broke in half.
According to the PPP publication, grease fittings can plug if dirt or a foreign object prevents the spring under the ball bearing from working properly. Old grease can also plug the channel inside the zerk, especially on tools only used once a year. If a fitting won’t take grease, replacing it is often easier than cleaning it, and will prevent incidents like the plow story. Use a grease fitting thread gauge so you replace a fitting with an exact match.
Dirty bearings. If you over-grease bearings exposed to dusty and dirty environments, grease can attract dirt particles. Eventually, dirt works into the bearing. It’s one of the reasons why bearings wear out prematurely.
You may not realize a bearing is attracting dirt through grease on the edges until it fails. Checking for excess grease and wiping it away is a good practice, the publication notes.
No grease vs. too much. “Believe it or not, many experts told us they view over-greasing an unsealed bearing assembly as just as bad as not greasing it at all,” Whitford says.
For a bushing on a pivot point or pin and bushing, pumping in grease until it comes out is acceptable, Whitford reports. Wipe excess grease away. Pumping too much grease into rotating bearings can blow out a seal or shield. Then, you no longer have protection against water and dirt entering the bearing.
If you want to get precise about how much grease you pump in, the publication outlines steps to measure grease in ounces, and calibrate the number of pumps needed for each bearing.
Dry bearings. When installing a new, dry bearing, grease it first, especially if it’s a tapered bearing. Installing it dry won’t get grease into the center of the bearing through a zerk. Tools are available to help grease new bearings. Select either a small canister that places the bearing over a spindle and forces in grease, or a bearing packing device that pumps grease into the center of the dry bearing. See the publication for more details.
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