In the Shop: Too Much Is No Good

October 17, 2012 01:13 AM

When it comes to repair and maintenance on farm equipment, the strategy "If a little is good, more is better" can backfire. Here’s a list of situations where moderation and restraint can reduce the need to repair repairs:

Overtightening lock collars.
Excess hammering on lock collars can crack the eccentric shoulder of a bearing’s inner race. That locks the collar only to the eccentric shoulder, leaving the majority of the inner race inside the bearing free to move on the shaft. The result: the shaft gets hogged-out by the movement of the bearing race, and both the bearing and shaft must be replaced. A firm tap or two with a punch and hammer are all that’s needed to secure a lock collar to a bearing. The set screw on a lock collar is merely insurance against movement once the collar is "locked."

Overtightening flared fittings on hydraulic hoses.
Flared fittings are designed to slightly deform and seal under moderate torque. Cranking on wrenches until the blood vessels in your forehead begin to throb risks cracking the fittings, with resultant leaks. Instead, use one hand to grasp two wrenches and squeeze them together for the final "snug." If it leaks, tighten it enough to stop the leak. It’s simpler to retighten an undertorqued, leaky flared fitting than to overtighten, crack it and have to buy replacements.

Jamming jam nuts. Jam nuts on tie rod adjusting bolts, belt tensioners and other applications need only be snugged 1⁄8-turn after firm contact with the companion nut. Cranking on jam nuts until they absolutely won’t move puts incredible torque against the threads between the nuts and can distort the threads of the shaft or bolt. Removal then requires replacement or repairs with a thread-cleaning die.

Overgreasing bearings. The phrase "pack a bearing" makes it seem like the more grease in a bearing, the better the bearing will perform. Not true. The grease in bearings serves two purposes: to lubricate and to cool. Rotary motion circulates grease inside a bearing, exposing warmed grease to cool surfaces. In case study after case study, bearing failures were traced to overgreasing. The bearings were packed so full of grease there was no circulation and no cooling, and the bearings failed. How to know when a bearing has enough grease? Lubrication intervals in owner’s manuals and on machine decals are calculated to optimize lubrication and cooling. (If it seems odd that a small 1" bearing is supposed to be lubed every 10 hours while a big 2" bearing is recommended to be lubed only every 200 hours, it’s because engineers put the cheaper bearing in an easily accessed location for easy replaceability, and buried the pricey bearing deep inside the machine.)

Using high-viscosity gear lube.
Thicker viscosity gear lube isn’t always better than "thinner" gear lube. As with grease, gear lubricant both lubricates and cools components in gear cases. Gear lube must be thick enough to not squeeze from between gear teeth, but thin enough to be slung against cooler gear case walls, which act as heat exchangers. Replacing 80w viscosity gear lube with 180w viscosity lube increases the chance of the gear case overheating and related problems. Use only the lubricant specified in the owner’s manual for a specific gear case.

Overtensioned roller chains. High-speed roller chains live or die by the film of lubrication between their pins, sideplates and rollers. Extreme tension on roller chains squeezes lubrication from between those components, leaving metal against metal. The proper tension for a roller chain depends on its load, its speed and the length of run between sprockets. In general, it’s better to be slightly "loose" than bow-string tight.

Overlubricated chains. Seed unit drive chains on planters work better with minimal lubrication. They run at low speeds, don’t build a lot of heat and are in a dusty, gritty environment. Lubricants, especially thick, sticky ones, attract grit and increase wear. It’s often better to operate planter drive chains "dry" or with minimal lightweight lubricant. However, common sense dictates lubricating planter chains that will sit outside during rain delays or off-season storage. Use a wrench or turn seed transmission drive wheels by hand to get chain lube to every link on every chain. Rotate chains several revolutions to work lubricant between all links and rollers for optimum protection.

Cool Tool

Removing the bolt or nut from the back side of a starter can be a challenge. Half-moon wrenches help, but most equipment manufacturers offer wrenches with specific bends and angles to access those nearly inaccessible fasteners.

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Spell Check

11/5/2012 05:53 PM

  Lubricating equipment, whether it's the grease, engine lube, hydraulics, rollers and chains - synthetics are the most cost effective product choice. Your vehicle and equipment dealer may not like you to use synthetics because he needs your business so he promotes petroleum based oils product options - get my drift?

4/4/2013 04:34 AM

   I've been listening to this argument about overgreasing for decades. We ran a custom silage business for about 20 years. The day that I decided to put grease zerks in the dust caps on our tandem axle wagons our wheel bearing problems disappeared. Filling that hub with grease not only lubricates but it stops dirt and water from entering. Normal temperature changes will put moisture in a hollow space! The main reason that those bearings that were "over greased" once fail is that they are forgotten. Just as any bearing needs repacked periodically grease still needs to be added to these "full" bearings. The only grease the rollers ever see is what is trapped betweeen the two races, the rollers and inside the cage. If not added to frequently, even in a full hub, this grease will be depleted and need replacing. A few squirts with a grease gun once a week is much easier than a full off the spindle repack with a new seal. We would have worn ourselves out repacking 40 bearings a year! These wagons wore out multiple sets of tires without ever opening up the hub. The two or three failures I can think of were due to a cracked hub or a broken bearing but never heat damage. But again, you have to add grease at least once or twice a year. Another idea is to lubricate the outside of all bearings before they go into storage, especially outside. That little bit of rust that can form where the seal has made a shiny surface is a sure way to take that seal out.

4/4/2013 04:39 AM

  I for got to mention that a $3 tube of grease to fill the hub is a lot cheaper than a $14 seal to replace!​


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