Bal-tec™ Home Ball Material Selection
You need some balls just like the sample, but how do you find out what it is? Or you may need help in choosing the right ball material for a particular application. The safest place to start is with the application itself. What does the ball do?
"Bearing balls" is the general term for any hard steel ball that will function in a roller bearing application. Common materials are hard chrome steel 52100, C/S, 440C hard stainless steel and carbonized high carbon steel. High speed steel might be added to this list for severe and high temperature applications.
If it is a ball bearing application, the most likely material is chrome steel which is 52100 chrome alloy steel. This is a relatively inexpensive material. This material is very hard, at about 62 HRC (Hardness on the Rockwell "C" scale). It is highly magnetic. It is not corrosion resistant, it will rust easily. Chrome alloy steel balls comprise about 90% of all balls manufactured. This material is a high carbon (1.00%), chrome (1.36%) alloy steel that will harden into the 60 - 65 HRC range when oil quenched from a soaking temperature of 1475 ° F. The hardness usually ends up at 62 HRC. The stress relieving or drawing temperature is 325 ° F. This does not mean that this steel can be used up to this temperature. We have run repeated tests where we elevated the temperature to 325 ° F. In the first three cycles, the samples dropped one point of HRC each time they were treated. It begins to lose its hardness at temperatures above 300 °F. It is a fine grade material that can be precision ground and lapped spherical within a few millionths of an inch with a sub micro inch surface quality. It is highly magnetic in the sense that it will be attracted by a magnet.
Chrome steel balls can be modified by grinding with conventional abrasives. Holes, shapes and threads can be generated by the Electrical Discharge Machine (EDM) process.
51100 steel is a very low alloy chrome steel that was widely used during WW II as a means of conserving chromium. It is more susceptible to stress cracking during the quenching cycle of heat treating than the more conventional 52100 chrome alloy steel. This material is highly magnetic. It will through harden in reasonable sections. It will harden to 60 to 65 HRC. With a 325° F draw, it will average 62 HRC.
We carry a hugh inventory of thousands of sizes and different qualities of this material. Click here to view our available inventory of chrome steel balls in our shopping cart program.
See Bearing Steel, for more information.
The third possibility is that, it is a case hardened carbon steel, i.e. hard carbon steel. For the most part, these less expensive balls are used in cheap bearings for casters, conveyors, bicycles and toys.
This material is highly magnetic. It has a thin carbon rich layer, cooked into the surface, that is then hardened to the equivalent of 60 HRC. This material is extremely rust prone. These balls are manufactured from low carbon steel wire, i.e. type 1018 steel. The ball blanks are cold headed, flashed and ground. They are then heated to 1700 °F in a very carbon-rich, gaseous environment to develop a high carbon case or shell in a rotary hearth furnace--carbon is literally cooked into the outer surface of the steel balls. After cooling, they are re-heated and oil or water quenched, depending on size. Next, they are tempered at 325 °F to relieve the stresses and to reduce the hardness slightly so they won't be brittle. After carbonizing, this material may be heat treated to the equivalent of 60 HRC. Because of the thin hardened layer, a special micro hardness test must be used to evaluate the hardness. It should be remembered that the hard outer surface is only a thin case or shell. Finally, these balls are ground and polished.
Soft low carbon steel (type 1018; 0.18% Carbon, 0.8% Manganese, balance Fe - Iron) balls are produced commercially in most common fractional inch sizes, up to 1 inch ( 25.4 mm). These balls are ground round with a highly polished decorative finish.
We custom produce soft, low carbon steel balls in the entire size range from subminiature to 17 inches (432 mm). These custom made balls can be supplied as: precision machined only, precision ground, or precision ground and polished. This material can be easily drilled, threaded, and otherwise machined with conventional chip-making machines. Type 1018, soft, low carbon steel, balls are very weldable.
This material is strongly attracted by a magnet. These balls are the least expensive metal balls. See our Shopping Cart for available stock.
The last common bearing material is high-speed extremely high temperature alloy steel. This is only found in hot bearing applications. High speed steel balls are usually produced from type M50 or M10 steel. Many of the "T" type high speed steels are almost impossible to purchase today, High speed steel's main property is its very high temperature resistance. High speed steel will remain hard even at red temperatures. High speed steels are generally harder than the standard chrome steel. It is typically 65 HRC. This material is highly magnetic. We can usually grind this material with expensive cubic boron nitride abrasive. It can be drilled, threaded and otherwise machined using the EDM process (Electro Discharge Machine).
|M10 High Speed Steel|
Precision balls can be produced from this material, but there is really no good reason to use it. The properties of this material have no advantage over the standard 52100 chrome alloy steel, which is less expensive and more readily available.
06 Tool Steel finds frequent use for the production of large and very precision balls. It is reasonably machinable. It is readily available in large diameter, cylindrical form. It will through harden, even in very large diameters. It can be ground and lapped to a very high quality.
|06 Tool Steel|
Ball screws are very similar to ball bearings in that they generally use either chrome steel or type 440C hard stainless steel. A peculiarity of ball screws is that they typically have a load ball and the next ball is a .001-inch undersized spacer ball, and so on. One half of the balls are load balls and one half are spacer balls.
In exotic aerospace or life threatening situations, you should obviously not use home-grown tests to validate materials since sophisticated alloys like high-speed steel, Stellite® or HASTELLOY® may test similar to other common materials, but in fact have extremely different physical properties. The Stellite® alloys most most frequently used for balls are Star J or number three. They are very hard and wear resistant. See our page, Radiations Hardened Kinematic Systems for more information on Stellite®.
Another place where balls are widely used is in the plumbing of pneumatic and hydraulic systems. Ball check valves, flow control valves, pressure relief valves and pressure regulating valves all use ball and seat combinations to perform their functions.
In pure hydraulic oil systems, the most common ball material is chrome alloy 52100 steel. This ball will be very hard, and highly magnetic, but it is not corrosion resistant and will test positive in any of the corrosion tests. In the grinding spark test it will be orange in color with many side bursts, as the carbon burns with the oxygen in the atmosphere (incineration).
Some high-end hydraulic systems may use type 440C stainless steel. This material is highly magnetic, it is hard and it will not react to any of the corrosion tests. In the grinding spark test, it will have a short red spark with almost no side burst. In the plumbing for the food processing industry, HASTELLOY®, Stellite® and even Tungsten Carbide (TC) balls are often used.
Stellite® is very hard. It is almost non magnetic. It is extremely corrosive resistant. When spark tested, it will give off almost no indication at all, outside of a few red tracers. HASTELLOY® is tough but not very hard. A file will cut it with ease. It is an extremely corrosion-resistant material. The cylindrical bar stock to make these balls costs us $71.00 per pound in 2008. High quality balls of any size can be produced from this material.
Tungsten-carbide is very very heavy. Many times all you have to do is to heft it to distinguish its enormous mass. It will not react to any of the corrosion tests. It will emit no spark at all when ground with a conventional abrasive wheel. It is the hardest of all synthetic materials. If you look at this material critically, it is not a silvery metallic but is a dark gray in color. Tungsten-carbide is only slightly magnetic and is usually easy to distinguish from steel. See our shopping cart for available stock.
See our web page on Tungsten Carbide for more information.n
In tap water systems, brass balls are often used, although type 316 stainless steel will show up in high-end systems. The bright golden color of the brass gives it away. It is dead soft. It is entirely non-magnetic. The corrosion tests will only brighten the gold color.
Is the ball hard? Measuring the actual hardness of a precision ball is a complicated and difficult procedure. To make a shop test of hardness, first procure a brand-new, flat, fine toothed, mill bastard file. Hold the ball to be tested in the jaws of a set of clamping pliers like vise grips.
Is the ball corrosive resistant? There are a number of fast tests that give a good indication of the corrosion resistance of a ball, but most of these tests require the use of caustic chemicals.
One method that uses ordinary table salt can give a good indication, but it takes a full 24 hours to produce results.
A good fast test of corrosion resistance is to immerse pre-cleaned test balls in a 5 percent solution of nitric-acid in alcohol. This "Nital" solution will turn all steels a light to dark gray in just 2 minutes. It won't change the color of corrosive-resistant materials.
An even better test is the copper-sulfate test. This solution consists of copper-sulfate crystals dissolved in a 6-percent solution of sulfuric-acid and water. A drop of this solution on the surface of a clean steel ball will immediately form a bright spot of copper-plating. This solution will not affect any of the corrosive resistant materials within a two-minute period, but may react to hard ferritic or Martensitic stainless-steel after a long period of exposure. See our picture gallery page.
Is the ball magnetic? Here we must be a little careful. Many materials that most people consider totally non-magnetic, like 300 series stainless steels, can become slightly magnetic when it is cold work-hardened. Remember that commercial balls are made by cold-heading the blanks from wire. Then they are rolled between two hard steel plates to remove the cold heading flash from them. Both of these processes generate strains in the balls that will make them at least slightly magnetic.
Look at our papers on "How Balls are Made."
Use an ordinary pocket magnet to test for magnetism, not one of the very powerful rare earth magnets. If the magnet strongly attracts the ball, it is one of the steel materials. If it doesn't attract it at all, or if it only has a very slight attraction it is one of the corrosive resistant materials, or else a totally nonferrous (without iron) material.
It may sound obvious, but look at the sample ball. For many applications on board ships, it is not unusual to find brass, bronze, or aluminum-bronze balls. It is also common to find these materials in plumbing and valve applications. Clean the ball with a strong detergent; brassy materials will be a golden yellow color. Brass and bronze are totally non-magnetic while aluminum-bronze will be very slightly attracted by a magnet.
You may find after cleaning that your ball isn't metal at all, but rather one of the plastic ball materials.
is a fairly common plastic ball material. It is heavier than most plastics and quickly sinks in water. It is very white in color. It will actually feel slippery to the touch. This material is the most corrosion-resistant plastic material. This material will operate at the highest and the lowest temperatures of any plastic ball material. This is one of the most expensive plastic materials.
See our PTFE ball stock in our shopping cart.
The spark test can be a very effective test procedure to help identify a material. Use an ordinary shop grinder for this test. Ideally use a course (40) grit grinding wheel. This test is more effective in an almost dark area. The grinding wheel should be dressed to remove any metal embedded in the surface.
Lets break the appearance of the sparks coming off the grinding wheel down into three categories:
The best possible aid to spark testing is to have balls of known materials to compare the sparks with. Break the spark into the three characteristics of color, length, and incineration (side sparks or bursts). Add the information regarding the hardness, magnetism and corrosion resistance and you will be able to nail down ninety five percent of the ball materials.
Please give our office a call at (323) 582-7348 with any questions, or toll-free at 800-322-5832.
To the quest of determining the material, we must add that of determining the required quality.
For bearings and ball screws with balls from 1/16" (.0625 inch, 1.59 mm) to 5/8" (.625 inch, 15.9 mm), A.F.B.M.A. grade-25 is a good commercial quality that is good enough for most commercial applications.
Request a ball grade chart, printed on plastic, from our office to better understand the quality and grade specifications and one will be sent to you free of charge. It is available as a download from our web site.
For larger and smaller balls, a lower quality grade may be used for economic reasons. Grade 50 or grade 100 are usually available as an economic alternative to grade 25.
In valve and plumbing applications, much softer corrosive-resistant materials are often used. It is very expensive to produce the highest quality balls in these soft stainless steel and non-ferrous materials. The high quality balls in these materials are usually Grade 100 and good commercial quality balls are Grade 200. Call our office for technical assistance.
Type 1018 soft mild steel has a very low carbon content. This steel is not hard. It can be machined, drilled and tapped. This material is highly magnetic. It will be strongly attracted by a magnet. This is one of the most weldable steel alloys. Hardness is rated at 28 HRC.
17-4 PH is one of the family of precipitation hardened nickel based alloys. It combines high strength and good corrosion resistance with moderate hardness. It is hardened by soaking at an elevated temperature for a period of time.
The most common soaking temperature is 900° F. This heat treating is referred to as H-900. In the solution annealed condition, this material has moderately good machining properties. 15-5 PH is another of the common PH alloys.
If the application isn't too severe, type 316 stainless steel may be used. The 300 series stainless steels are basically an alloy of 18% chromium and 8% nickel with the balance ferrite (iron). This material is dead soft at about 30 HRC (Hardness Rockwell "C" scale), and is almost non magnetic in the annealed condition.
In pneumatic systems, there is usually water or water vapor present. To prevent rust, type 316 stainless steel is used. The spark test will yield only tiny red tracers. This material will not respond to any of the corrosion tests. It is almost non-magnetic. It is dead soft and the file test will put an immediate flat on the ball.
Type 420 hard stainless steel is the material widely used in Europe. It is very similar to type 440C, which is more widely used in the United States. Type 420 is not quite as hard as the type 440C. One of the advantages of 420 over type 440C is that it has a higher magnetic permeability, so that it is attracted more strongly by a magnetic field.
440C Stainless Steel is one of the most amazing standard ball materials. It is a very high chromium, high carbon, martensitic stainless steel. Martensite is the very hard state of a high carbon steel. When heat treated from the spherodize annealed condition, it forms an extremely fine grain structure. For hardening, it must be raised to 1900° F. It will harden to 58 - 63 HRC. It is usually at the low end of this range, when tempered at 400° F
If the bearing is used in a corrosive or wet environment, it may be a type 440C hard martensitic stainless steel. This material is very magnetic and it is hard, but it is not as hard as chrome steel. It is about 58 HRC (Hardness Rockwell "C" scale). This material is only mildly corrosive resistant and will only respond to corrosion tests with slight pitting. It will eventually corrode in tap water and will not stand up to sea water at all. It is widely used as a premium bearing material and it is the top material for use in gaging products. See our article, Stainless Steel Balls, Type 440C Hardened for more information.
1100 series aluminum is commercially pure aluminum. It is a very light weight material that is a silvery white color, one of the natural base elements, and very ductile. Balls made of 1100 series aluminum are often used as closures. They are squashed or upset to permanently close a hole (an inside diameter). It is difficult to locate this material in less than mill-run quantities.
2017 aluminum is a copper alloy of aluminum that was originally developed for the manufacture of rivets. Its number one quality is that it can be safely cold-headed, which makes it an excellent choice as a material for precision balls. This is the aluminum alloy specified by Mil-B-1083, the generally accepted military specification for precision balls. This alloy has also been chosen by the AFBMA (Anti Friction Bearing Manufacturers Association as a standard ball material. This material is usually heat treated to the "T4" condition. This is not a good choice if the ball is to be anodized. High quality balls can be produced from this alloy.
|Aluminum Alloy 2017|
2024 aluminum alloy is an aluminum copper alloy. It is a high strength material, widely used in aircraft. It can be cold headed. The tensile strength of this alloy can be improved by heat treating. This alloy is not a good choice for hard anodizing as the segregation of copper will form voids and can even cause incineration of the metal during the anodizing process.
Aluminum balls of all type are often used as closures by compressing them to seal a close fitting hole.
6061 Aluminum alloy is a widely used, readily available, aluminum material. This material should never be cold headed--it can develop internal fissures that will lead to catastrophic failure. This alloy has much better machining qualities than 2017 alloy. This alloy is an excellent choice when the balls are to be hard anodized. The tensile strength of this alloy can be improved by heat treating. This aluminum alloy is relatively light at 0.098 lbs/ cu in.
It is very slightly magnetic. An aluminum bronze ball will roll towards a powerful magnet. This material is very resistant to sea water. Some alloys of this material can be heat treated to increase its hardness and tensile strength, but the hardening process reduces corrosive resistance. It is a very good electrical conductor.
A286 is one of the exotic Space Age materials. It has good wear properties. It is corrosion resistant. This material must be heat treated to develop its best physical properties. This material is very expensive. Very high quality balls can be produced from this material.
High quality steel balls of both chrome steel and hard stainless steel can be treated chemically to color the surface black. This black iron phosphate actually penetrates the surface so that the original size and surface quality is not affected. The most common application for this surface treatment is to provide identity for these balls. In some bearing and ball screw applications, two different size balls are used in the same device. The larger diameter balls are load bearing balls, and the smaller diameter black balls are used as spacer balls.
We manufacture and stock a large variety of brass balls. Brass balls are gold or bright yellow in color. The Standard alloy is 70-30, which is 70% copper and 30% zinc. The only major problem with the metallurgy of brass is segregation. This is due to the high melting point of copper (3000° F) and the low melting point of zinc (800° F). This material is quite ductile and very malleable. It is corrosive resistant to tap water, but does not stand up well in sea water. It is nonmagnetic, an excellent electrical conductor, and has excellent solder ability with soft solder, but may require chemical cleaning to remove an oxide layer. Brass has a hardness of less than 30 HRC, is very machinable, and it may be drilled and tapped easily. Brass is a relatively heavy material at .275 - .316 lbs/cu in (7.60 - 8.75 g / cc).
Naval Brass or Naval Bronze is very similar to brass, but has an addition of 0.5% to 1.0% tin. This small addition gives to material good corrosive resistance to sea water.Naval brass or bronze is a relatively heavy material at .305 lbs/ cu in. We will custom manufacture special alloys if the material is commercially available. Brass balls are precision ground and polished. They can be produced to AFBMA standards when required. We produce brass balls in all sizes from the sub-miniature to very large diameters.
We manufacture copper balls in the entire range of sizes from sub-miniature to several inches in diameter. Pure copper, as well as the many copper alloys, can be used to produce highly accurate precision balls.
Copper, usually oxygen free, has excellent electrical and heat conductivity, as well as good corrosion resistance in many harsh environments. It is nonmagnetic. It is sometimes annealed after all forming and machining is completed, to enhance its electrical properties. It is extremely malleable and ductile. It is very soft, but it is gummy and very difficult to machine, tending to gall easily. It is very solderable, and it is very corrosive resistant to sea water. Copper has a distinctly red color.
Diamond-impregnated balls are used to lap the spherical radius in ball valves. They usually have a stem or handle attached to facilitate holding during the lapping process. See our Diamond Impregnated Ball Lap page for more information.
An obvious use for gold is for jewelry. The nobility of gold — meaning its resistance to corrosion — and its good electrical conductivity leads to use in electrical applications. Gold has a high level of x-ray opacity and good bio-compatibility, which leads to its use as x-ray markers in medical applications. As gold is such an expensive material, we do not maintain a stock of gold balls.
Hevimet is usually sintered from powdered tungsten and powdered copper. Its very heavy weight makes it an alternative to lead in some uses. It is machinable, and unlike lead it is biologically safe. Ball's made of this material are used as counter-weights, and to add mass to mechanical structures.
High speed steel such as M50 and M10 or T15 are usually reserved for hot end bearings and high temperature ball screw applications. These materials are not corrosive resistant and will react to any of the corrosive tests. These materials are very hard. They will test up to 65 HRC. They will be strongly attracted by a magnet.
When spark tested, they will give short red tracers with almost no side bursts. These balls are often supplied in very high quality grades, up to A.F.B.M.A. Grade 10.
Inconel™ 7-18 is truly an aerospace metal. Inconel is hard and strong. It will continue to perform at high temperatures. It will also perform at temperatures so cold that hydrogen is a liquid. These low temperatures are so cold that there is a special word for it, cryogenic.
The highest quality is required for these aerospace oriented balls. In many cases, every single individual ball must have its own pedigree accompanying it. This will include the physical and chemical analysis of the individual bar of material, an ultrasonic examination, and the heat treating process that was performed on it. Along with this will be the diameter of the ball on three orthogonal axii and three polar charts of the roundness taken on three orthogonal axii.
A rocket engine using inconel balls depends on the integrity of each individual ball, making them crucial parts of the rocket engine. In addition, Inconel™ is highly corrosive resistant. It is precipitation hardened. This metal alloy must be heat-treated to develop its good physical properties. Care should be exercised in specifying the desired heat treatment as the furnace time for some processes may be very long and therefore, very expensive.
We manufactured Inconel™ balls for the Apollo and Space Shuttle programs. Inconel™ is a very expensive material, and may require considerable lead time just to procure the raw material.
To see our stock of Inconel™ balls, click here.
There are a number of different Monel™ alloys, a trademark of Special Metals Corp.. The basic alloy has a minimum of 23% copper and minimum of 60% nickel with small amounts of iron and manganese. This material is very tough but not very hard. It is not heat treatable. Monel is used in very corrosive environments. It is excellent in salt water applications such as valves for sea water. It is also used in the food processing industry.
We make Monel™ balls in a wide range of sizes. Due to its relatively soft nature, AFBMA grade 200 is the normal quality specification, although grade 100 can be achieved with some difficulty. It is relatively soft at about 38 HRC, and it is difficult to drill and tap.
MP35N finds use for check valve applications where no other metal could ever survive. In down hole control valves where the chemistry of the environment would eat a stainless steel ball, balls made of this material will last indefinitely.
This material is so tough that producing precision balls from it is a major problem. It cannot be cold headed at all. The forging temperatures are extreme. Like many of the exotic metals, MP35N can be lapped to a very high level of quality, once the spherical blank has been produced.
The word expensive was coined to describe this material. Delivery is also a problem as the material has to be special ordered.
Niobium, a high density material, is very malleable and ductile. It is widely used in body jewelry.
Platinum balls are widely used in high reliability electrical contacts. For this application, the platinum is alloyed with a small percentage of other elements. In the United States, it is usually alloyed with iridium; and in Europe, it is alloyed with nickel. These toughening and hardening metals have only a slight effect on the properties of the platinum. Platinum is the most noble of metals and is impervious to attack by most acids and bases. Platinum has one of the highest melting points of any metal (1768.3 °C, 3214.9 °F).
As platinum is an expensive material, we do not maintain any platinum items in stock .
Unlike most other plastic balls, this material is a thermosetting plastic. This means that once this material has been heat cured in the mold, it will not melt again. You can raise the temperature of this plastic until it incinerates, but it will not melt. This material is much harder than any other commercially available plastic ball.
It must be compression molded or catalyzed in a mold at high temperature, which makes it much more expensive than thermo plastics that can be injection molded.
René 41 is an extremely tough high temperature nickel-chrome-molybdenum alloy. The machinability of this material is the very lowest of any commercially available alloy. But once the blank is machined, grinding and lapping are no problem. High quality balls can be produced from this material.
Tantalum balls or beads find frequent use as radiographic markers, because of their bio-compatibility. These balls can be implanted to form three dimensional markers for orthopedic evaluation after surgery. A ring of these radio graphically opaque markers are used at both ends of stints and shunts, providing a well defined address for the implanted devices. This material is used as an x-ray-opaque tracer in medical implants. An attached ball will define the position of a catheter. Tantalum is a very dense heavy metal (Ta) atomic weight is 180.947, density: 16.6g/cm^3. Unlike tungsten, it is very ductile and malleable. It will produce no reaction with either hydrochloric acid ( HCL) or nitric acid (HNO3). When Tantalum is implanted in a patient, it must be processed according to specification ASTM F560 (Medical Grade).
See our sister site, www.tantalumbeads.com, for more information.
See our shopping cart for available stock.
Titanium Balls are made in two popular titanium materials. The first is basically pure titanium. This material, grade 2, is widely used in medical applications, where it is frequently used in body implants because it is very bio-compatible. The second, and by far the most frequently used alloy is 6AL4V (6 % Aluminum, 4% Vanadium) titanium. This alloy is available in a variety of wire and bar forms for easy processing into precision balls. Satin finished titanium balls are used as calibration devices for optical inspection devices.
Titanium has an unusual hexagonal close-pack atomic structure, as contrasted with a face-centered or a body-centered cubic of most metallic elements.
Tungsten has one of the highest melting points of any available metal. This is one of the heaviest metals. It is hard, tough, and non-magnetic. This metal is expensive and it is very difficult to machine, grind, or lap. Very high-quality balls can be produced from this material.
Waspaloy is one of the older exotic alloys used in high temperature applications. This material is very expensive and is only available in a limited number of shapes.
Aluminum Oxide is an almost white ceramic. Chemically it is Al2O3, also known as alumina balls or aloxite balls . This material is extremely hard. It has excellent electrical insulation properties. It is one of the least expensive and most widely used ceramic ball materials. It is very wear resistant, and it is very stiff with a young's modulus (YM) of elasticity of approximately 45,000,000 pounds per square inch. It can only be used in bearings at low speeds and very light loads. Star J and #3 are the alloys most frequently used for balls. They are very hard and wear-resistant.
Silicon Nitride (Si3N4) ceramic has become the standard ceramic ball material for hybrid Ball Bearings. This material is very hard, over 2000 Knoop, and very wear resistant. The weight of silicon nitride balls is only 40% of steel at 3.2 grams per cm³ (cubic centimeter) .
This material is hot isostatic pressed from 1 to 3 micro powder, has excellent fracture toughness even at elevated temperature, and ball quality as good as AFBMA grade-5 can be achieved on this material. Silicon nitride has excellent dielectric properties and extremely high resistivity (insulating properties).
For more information on engineering materials, see the site matweb.com .