Reel Bearings - 201 Ready for bearing overload?
Introduction: Ready to move on to "Reel Bearings 201?" The second installment of the tutorial continues to build on the fundamentals presented in Reel Bearings – 101. It covers ceramic bearings, bearing corrosion, lubrication, and other related topics. Bust out those notebooks, its time to talk bearings...
Ceramic and Bearings: Advanced ceramic materials were initially used in the early-60's, mostly as coatings on power turbines and electrical generating equipment. The hardness, electrical resistance, and light weight of the material made them ideal for these applications. Not long after that, advanced ceramic materials began to be used as man-made abrasives. Today they are used in a number of common products, yet most don't even recognize them.
Now when I say ceramic, I'm not talking about the same type that is used in your grandmother's china. I'm talking about industrial ceramics – typically made from compounds of synthesized powders which are joined under extremely high pressure and heat. (In fact, many closely resemble natural sapphire and ruby, and advanced ceramics have a harness that approaches diamond.) Besides, a table setting of fine dishes made from industrial ceramics would cost millions of dollars!
Industrial ceramics are extremely resistant to wear, lighter than most metals, relatively strong, and are corrosion resistant. If there was anything bad to say about them, it would be that they will brittle fracture under stress, if there are surface pores, cracks or flaws from the manufacturing process. That was the problem with early ceramics used in industrial applications, but that was a long time ago – and no matter what you've heard, most manufacturing processes have been improved to mitigate fracture defects, since that time!
Industrial ceramics began to be used for bearing materials when the need for alternatives to special corrosion resistant metals was identified by the chemical industry. Initially, stainless steel balls were coated with ceramics, and later manufacturing processes were developed to produce totally ceramic balls. Today, you can even get bearings that are completely made from ceramic – but they are quite expensive and aren't always available in the sizes you need for a reel.
Hybrid ceramic radial ball bearings usually have metal (e.g. 440C Stainless Steel) races, cage, and shields, with either completely ceramic or ceramic coated stainless steel balls. (Except for the balls, most other components are manufactured as described in the previous bearing tutorial.) They are relatively cost effective, since the balls are the only incremental expense, when compared to stainless bearings. They weigh approximately 40-60% less than their stainless steel counterpart.
Ceramic and ceramic coated balls typically have a surface finish that is 5 times finer than stainless steel balls, so wear of the races and cages are significantly reduced, and bearing lifetime typically increases (with lubrication) up to 5-10 times longer than an all-stainless bearing. Although ceramic balls can be used without lubrication, you can extend the fatigue life of the metal components with lubrication. Lubrication also mitigates corrosion of the metal components (but more on that later), since ceramic balls will not corrode.
Ceramic balls can be fabricated so they are extremely uniform in size (diameter) and roundness. It is not unusual for the balls in a bearing to all be within +/- 1 micrometer in diameter, and +/- 0.1 micrometer in individual roundness! So, it's no wonder that much less ball slip and friction is produced, given the very fine surface finish and uniform balls. Most ceramic hybrid bearings are at least ABEC 3 or higher, primarily because of the stainless steel components!
Because all-ceramic balls weigh roughly 60% less than a stainless steel ball, the bearing will have reduced centrifugal loads as the balls spin against the races and cage. Reduced centrifugal loads combined with the reduced slip, results in higher attained speeds and less bearing vibration and noise. Although they can sound a little rough when new or after cleaning, they should quiet down after the lube has had a chance to disperse and run-in. However, one of the downsides with lighter and more precise bearings is that they can be significantly affected if over-lubed or get fouled with debris and/or water, due to the lighter ball weight, and tighter tolerances and fit in the bearing. Debris may not be as readily cast off, as it otherwise would, and instead will often circulate around inside the bearing between races, balls, and the cage. Consequently, ceramic hybrid spool bearings may need more frequent cleaning (when compared to lower quality bearings), especially when used in a reel for shore fishing.
Manufacturing techniques for making advanced ceramic materials are closely guarded by manufacturers. In fact, the chemical composition for the trace and binding chemicals in the Aluminum Nitride, Silicone Carbide, Silicone Nitride or Zirconium Carbide powders is seldom disclosed, even to major customers. However, the basic process is called 'sintering', which generally involves pressing the powder slurry in a die under super-extreme forces, and then heating it to very high temperatures to burn off oxides and unnecessary binding compounds. Some companies have spent decades perfecting the process, so that pores, cracks, and surface flaws are not introduced in the process. Especially since, a ball that is manufactured with such defects could literally explode, even under light loads!
Ceramic balls for bearings (or coating for stainless steel balls) are also formed by sintering, but they are made slightly larger than the final size. Diamond slurry mechanical lapping machines are used to achieve the finished size, and continuously lapping for up to 2 months is not unusual for some ceramics. The same quality checks and controls are used while making ceramic bearings to ensure the product meets final specifications. In addition, process controls are often implemented to detect any surface flaws.
Here's a tip you can use when you buy ceramic bearings for your reel, to help ensure you are getting what you paid for. Although not necessarily "cast in stone", you can consider these items; ABEC 7 ceramic hybrid bearings and ABEC 5 and higher all-ceramic bearings are not usually greased (although they may have a light coating of oil, to preserve any stainless steel components); most ceramic materials will be white, black (or dark gray), or green in color, so be sure to check the balls on ceramic-hybrid bearings; the bearing will weigh about one-half as much as a stainless steel bearing in the same size; and hybrid ceramic bearings typically do not come with full-size pressed shields that cannot be removed, and usually come with no shield(s) at all or with removable shields.
Here's another tip, you may find useful. Ceramic spool bearings will typically run quieter and with less vibration, than conventional bearings in the same ABEC class. However, you may notice more vibration or noise from the reel, as you cast or crank it. Wait a minute, how can that be, especially if they run better? Here's an explanation: The noise/vibration could actually be due to several factors, which are really related to the higher spool speed, and much more braking action that occurs during a cast. Some spools, reels and brakes may not operate as smoothly at the higher speeds (since they may not be finely tuned, balanced or aligned, as they could otherwise have been). Lastly, the vibration/noise may be due to debris, excess or dried oil, or water that has fouled the bearing, causing noise to be amplified while vibration is transmitted to the frame (especially on large and more-open magnesium framed reels). The advantages of ceramic hybrid spool bearings may not be very discernable to an occasional angler, but ask one who spends a lot of time on the water, and they'll probably tell you that they cast just as far as regular bearings – but with less effort (and maybe even a little further too)! It should also be pointed out, that the braking system on some low-quality bait casting reels may not be able to handle the speeds developed by ceramic spool bearings, and overruns could occur!
I predict that more and more ceramic bearings and other components will be used in factory reels, especially those designated for use in salt water. Manufacturing advances will steadily drop ceramics prices, and consumers will continue to demand more performance from high-end reels in the future. The TD-Z and a few other reels already have ceramic spools, and Shimano, Daiwa and Okuma have supposedly been putting "super corrosion resistant" (ceramic?) bearings in recent reels. Who know, maybe 100 years from now, fishing reels won't even have brakes or drags – but will instead employ nano-ceramic bearing technology to brake and play line? Ceramic is the new "Holy Grail" for fishing reels!
Reel Bearing Corrosion: Stainless steel is pretty good at resisting corrosion in most environments. However, when you use them in a bearing, the stainless has to be heat treated to increase the surface strength of the metal. And there's the problem – the corrosion resistance of stainless steels decreases during heat treatment, because the structural composition of the metal has physically been changed, and it is no longer passive to corrosion. Over time in the wrong environment, the surface of most heat treated stainless steels can roughen, pit and generally degrade. It can even cause the metal to completely crack and fail if the stainless is under much stress (either from manufacture or from loading). Stainless steel bearing components are no exception, especially in a high sodium or chloride environment (i.e. saltwater).
Seawater contains approximately 3.5% of various salts by weight. The most predominate salt is Sodium Chloride, and there are smaller amounts other salts also present. Salts dissolve in water, to form ions which are loosely held by the water molecules. However, the bond with the water molecules will easily break, allowing the ions to affect other metals that may also be in contact with the saltwater (e.g. corrode).
Sodium and Chloride are especially troublesome for Iron containing metals, including common heat treated stainless steels used in bearings (which is usually made from 440C stainless steel.) Several different types of corrosion can occur on the stainless, and most will cause pits, blistering, and cracks to form from the surface into the metal. If left in contact with seawater, the stainless bearing metal can eventually fail, or may run rougher or cause problems with other metal reel components. Balls and bearing races are especially vulnerable, since rotation causes rubbing, which prevents their surface from forming a more stable oxide layer that would otherwise protect them from attack. [Heat treated stainless steels that don't rub, generally don't tend to be attacked as much by sea water, because of this stable oxide layer.]
What about brackish water? "Brackish water" contains dissolved salts in concentrations from .3% to 3.5%, and is not suitable as a normal source for drinking water. ("Fresh water" contains less than .3% dissolved salts.) Brackish water is usually found near sea water, and a few examples include salt water marshes, coastal inland lagoons, and even some deltas. Brackish water can also include some recovered Phosphate pits (like those found in Florida and other parts of the country), which can also have high concentrations of Sodium based salts. The bad thing about brackish water is that it also can contain high concentrations of microbes and other chloride based organisms, which can also attack the carbons in steels, especially metals under stress due to manufacturing processes. So, it is best to treat brackish water like seawater, and carefully wash your reels in a spray of warm tap water after fishing, and only use reels that are recommended for saltwater service.
Freshwater can still contain small amounts of salts, algae and microbes that would otherwise attack stainless steels, but the concentrations are typically so low that the attack rate is usually measured in years, rather than days (like in seawater). Even so, it may be a suitable practice to rinse your reels in warm tap water and dry them after use, especially if a major algae bloom is in progress on the water you have just fished. [The algae can live and grow in a reel (if they are in sufficient quantity and left undisturbed in puddles of water), and the chlorides left by the algae can attack bearings and other reel metals over a couple week period.] However on a freshwater lake under normal conditions, it is probably only necessary to shake out any water and dry the reel off, before storing in your rod locker.
Be sure to periodically check that drain holes are open and will drain any water or moisture from the reel. Some reels have drains on the bottom sides of the reel where a handle or palm plate attaches to the frame, and they can get plugged with debris, grease, or corroded, allowing pockets of water to form in the reel.
What about chrome plated and bearings made out of other materials? Reel manufactures have made bearings and bushings out of many different materials over the years. Brass, bronze, and other copper alloy bearings were used early on. However, they wore quickly and required frequent lubrication, but were fairly resistant to corrosion. Carbon steel was also used for reel bearing materials, and although it wore better, it was extremely susceptible to water corrosions and required constant cleaning and other care.
Chrome steels were initially used to plate softer bearing materials, in order to improve the surface finish and reduce wear. The Chromium, Manganese and Silicone in the steel makes the surface more durable than plain brass, bronzes and carbon based steels, and chrome has fair corrosion resistance if alloyed with Nickel. Chrome can also be polished to provide a good surface finish, with moderately low friction from slip. However as plating, it can blister, chip and flake off, which exposes the underlying metal to wear or corrosion.
Solid chrome steel is actually a form of stainless steel if nickel is present, and it resists corrosion fairly well, but is not very durable (can wear poorly, gall and even crack). Without the nickel, it is much more durable, but is not as corrosion resistant. Even so, some lower end reels are still being manufactured with chrome steel bearings and other components. The key is to keep them well lubricated, and dry while in storage, and rinse them immediately after use in saltwater. Some alloys of chrome steel resist saltwater corrosion better than others, so following manufacturer recommendations on use and maintenance is advisable. A few anglers have reported good success with the use of spray or gel moisture blockers, to protect against seawater contacting the outer races on chrome bearings and other metal reel parts. Beoshield T-9 and similar products contain anti-corrosion, rust prevention, and metal protectants, that supposedly last for months, in a fishing reel. Although I have not personally used Beoshield, I have seen it at several marine dealers.
Reel and bearing manufactures have dealt with the effects of corrosion on bearings in a number of ways. In fact, it is not uncommon to see combinations of the following used in a modern high end reel:
- Shield the balls from saltwater intrusion: This was the general approach that Daiwa used when they initially coined the terms "Corrosion Resistant Ball Bearing" (CRBB). The shield is designed to reduce entry of contaminants, like a seal, and bearing life in a saltwater environment increases up to 12 times that of a conventional stainless steel bearing. Other reel manufacturers now use similar shielded bearings.
- Layer the stainless steel balls with a coating of activated alumina: Activated alumina coatings are actually a form of industrial ceramic, and it forms a very tight and hard surface that prevents seawater from contacting the stainless. Some manufactures actually call this a quasi-ceramic coating, but whether it is or not is a matter of how the coating is applied, temperatures, thickness, etc. (Most processes actually lightly sinter the surface of the stainless with the activated alumina, which is similar to passivating the metal.) I think Shimano is now doing this to their corrosion resistant bearings and bearing life supposedly increases about 10 times that of a conventional stainless steel bearing in a saltwater environment. I also think Daiwa may also be doing this, especially when they use the term 'Super CRBB' – but I haven't been able to verify that.
- Use an all together different material for the bearing: Ceramic coated or all-ceramic balls will not corrode.
- Use a good lubricant: A lubricant that doesn't easily come out as the bearing rotates and doesn't wash out when you rinse your reel, keeps the balls from contacting seawater (if periodically replenished). The lubricant can also adhere to the balls to reduce friction.
Equip the reel with drain holes that will drain water from the reel. Oftentimes the line will pickup seawater and transfer it to the spool and it will drain out thru these holes.