To Grease Or Not To Grease?

Whether or not to grease a plastic bushing is a frequently asked question, or even just an assumption customers make (that they need to). While there are times where greasing is important, and times where it is absolutely critical, in most cases with many materials you will not need to.  Avoiding the need to grease a bushing is a strong advantage plastics have over metal in application. Many plastics are self-lubricating and can come impregnated with solid or liquid lubricants. Certain bushings, such as the Rulons, will never require grease. In general, if you want to switch from a greases metal bushing and are flexible on material, an oil-filled option would be quoted. The cost difference between oil-filled and unfilled materials is about 30% so you need to judge how important it is not to grease.

In the case where an unfilled bearing grade material is required, grease grooves can be machined into the part. These would come with a “grease nipple” or small hole in the bushing to permit application of the grease. This is common for applications such as kiln wheel bushings or sprockets. That said, there is one case where you *must* grease and that is if the demands of your application exceed the P/V/PV ratio of the plastic. P/V/PV needs to be under all three maximum limits for the bearing material; however, that’s a discussion that requires it’s own article.

If you are looking for grease-less bearings or have questions on our Redco bearing materials please contact us.

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Product Spotlight: Bushings and Bearings

Important note: Redwood Plastics does not stock many bushings or bearings. Customers view our bushing and bearing section and believe we have many off-the-shelf solutions and this is not true. What we can do, is take your available information on your application and try to come up with the best solution out of the many bearing-grade plastics we have available. Most commonly, these are the materials chosen:

Nylon: Handling 4000PSI and available in several grades with various fillers and performance enhancers, nylon is probably our most used bearing material. Nylon can be used in very large or small bushings, since nylon is available in cast or extruded forms. The extruded nylon can be made into very small bushings and larger bushings can be cast to net size and machined to completion.

Tuffkast: Nylon has drawbacks: water absorption, cold weather performance and impact. Tuffkast is a co-polymer that can provide the bearing properties of nylon with the impact resistance of polyurethane. The only reason it isn’t used more is that it’s still earning name recognition.

Polyurethane: Polyurethane is available in Redco 750 and 750 SXL bearing grades. The nice thing about urethane is if you need a mass-produced bushing because we can supply a precision-molded product, machining them to finish if necessary. Polyurethane has great impact resistance and can handle loads up to 2500PSI.

Phenolic/Composites: Composite bushings allow for the highest loads a plastic bushing can take. They perform extremely well high-load, low RPM applications. A benefit of composite bushings is that the material (or a liner on the inner diameter) is designed to create a lubricating film on the shaft, meaning no greasing in some applications. Some of these bearings can be purchased (though are not stocked) in finished sizes common throughout various industries.

Turnaround time for finished bushings varies, but is usually a few weeks. We can always supply just the bearing grade material to you in almost all cases to improve delivery or reduce costs if you want to machine them yourself. If interested in a finished bushing or bearing, unless you know exactly what you’re looking for, the first step is to complete our bearing design worksheet, available by clicking these links for a simple sleeve bushing or a flanged bushing. That can be emailed to sales@redwoodplastics.com and will be reviewed by the appropriate contact for quotation.

For more information on our bushing and bearing solutions, visit our website’s dedicated page here.