| Established in 1952 | |
Page: 2080 |
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 chrome steel, C/S, 440C hard stainless steel and high carbon steel. High speed steel might be added to this list for severe and high temperature applications.
1100 series aluminum is commercially pure aluminum. It is a very light weight material. It is 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 ).
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. This is the aluminum alloy specified by Mil-B-1083, the generally accepted military specification for precision balls. This is not a good choice if the ball is to be anodized. High quality balls can be produced from this alloy.
| Manganese | 0.7% |
| Copper | 4.0% |
| Magnesium | 0.5% |
| Aluminum | balance |
If it is a ball bearing application the most likely material is chrome steel, which is 52100 chrome alloy steel. This is 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. 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. It begins to lose its hardness at temperatures above 3000 °F.
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.
We carry a hugh inventory of thousands of sizes and different qualities of this material.
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.
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. The ball blanks are cold headed, flashed and ground. They are then heated to 1700 °F in a very carbon rich environment to develop a high carbon case or shell. After cooling, they are re-heated and oil or water quenched, depending on size. Next, they are tempered at 325 °F to relive the stresses and to reduce the hardness slightly, so that they won't be brittle. Finally, these balls are ground and polished.
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 cubic boron nitride. It can be drilled, threaded and otherwise machined using the EDM process ( Electro Discharge Machine ).
| C | Carbon | 1.0% |
| Mo | Molybnium | 8.0% |
| Cr | Chromium | 4.0% |
| V | Vanadium | 2.0% |
| Fe | Ferrite | balance |
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 |
|
| C | 1.5% |
| Mo | 0.25% |
| Si | 0.8% |
| Mn | 0.4% |
| Fe | Balance |
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 58HRC (Hardness Rockwell "C" scale). This material is corrosive resistant and will only respond to corrosion tests with slight pitting.
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 permability, so that it is attracted more strongly by a magnetic field.
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 homeopathic tests as sophisticated high-speed steel, Stellite® or Hastelloy® may test similar to other common materials, but in fact have extremely different physical properties.
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 corrosive resistance and will test positive in any of the corrosion tests. In the grinding spark test it will be orange in color with many side burst, as the carbon burns with the oxygen in the atmosphere.
In some high-end hydraulic systems they 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, Hastalloy®, Stellite® and even Tungsten Carbide ( TC ) balls are often used.
If the application isn't too severe type 316 stainless steel may be used. This material is dead soft, almost non magnetic and it will not react to any of the corrosion tests. There will be almost no spark when ground.
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.
Hastalloy® is tough but not very hard. A file will cut it with ease. It is an extremely corrosive 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.
In pneumatic systems there is usually water or water vapor present. To prevent rust type 316 stainless steel is widely 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 at about 30 HRC (Hardness Rockwell "C" scale) and the file test will put an immediate flat on the ball.
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 will give 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.
If the file glides smoothly over the surface of the ball, it is very hard (60 HRC).
If it bites a little when it starts to move, it is quite hard at (50 HRC).
If it cuts a flat on the ball then it is soft at (30 HRC) or less.
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. Take a cup of boiling water and stir in table salt, sodium chloride (NaCl), until no more will dissolve and salt crystals accumulate in the bottom of the cup. Clean the balls to be tested in a detergent soap solution and then with alcohol. Place them in the cup of salt water, for 24 hours. After soaking for 24 hours, Soft steel, chrome steel, high speed steel and hard carbon steel will all be brown with rust. 300 series stainless, Hastalloy, Inconel, Monel® and K-Monel® will be untouched. Type 440C, 416, 410, 420 stainless steel will only show a few pits or not be affected at all.
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 "Nitol" 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 golden 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 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, or 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 be surprised to find after cleaning that your ball isn't metal at all but rather one of the plastic ball materials.
Polyethylene and Polypropylene will float in water, while other plastic materials will sink. These ball materials are often used because they are inexpensive.
Nylon is one of the most common plastic ball materials. It is hard, it is tough and it is dense enough so that it sinks in water. Nylon is slightly hygroscopic, so it isn't the best plastic to be used in water applications.
Teflon 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 corrosive 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.
The spark test can be a very effective test procedure to help identify a material. Use an ordinary off hand, 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. Hold the ball in the same Vise Grip® pliers used for the file hardness test.
Hold the ball lightly against the rotating grinding wheel.
Lets break the appearance of the spark coming of the grinding wheel down into three categories.
#1. The color of the spark. Don't look at anything but the color. 440c and high-speed steel will give a very red spark. Chrome steel will give a bright orange spark. Hard carbon steel will give a nearly white spark. 300 series stainless, Monel® K-Monel® and Hastalloy® will give almost no spark at all. If you use a heavy pressure you may get a few tiny red darts.
#2. The length of the spark is the next characteristic to look at; 440c and high-speed steel will throw a short spark. Chrome steel will throw a medium long spark. Hard carbon steel will throw a much longer spark on the same wheel at the same pressure.
#3. The nature of the spark will very with the different materials. The free carbon in the steel incinerates or burns in the oxygen of our atmosphere and this forms a burst or side spark that comes off the main spark at an angle. In high alloy steels the carbon is tied up in high temperature combinations of chrome, tungsten, cobalt or molybdenum, so there is very little burst if any. This group includes type 440c stainless steel and the high-speed steels.
In materials such as chrome steel, which only a small percent of alloy the incineration or explosion of the spark is much more pronounced and occurs closer to the grinding wheel. There will be a lot of side sparks.
High carbon steel basically has no alloy, except extremely high carbon content, so there are lots of sparks up and down the streamers leaving the wheel.
There will be almost no spark with many materials like 300 series stainless, Hastalloy®, Monels® or Stellites®.
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.
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 specifications and one will be sent to you free of charge. It is available as a download from our web site; or if your need is urgent, we will fax you a copy.
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.
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.
This is an extremely tough high temperature alloy.
The machine ability of this material is the very lowest of any commercially available alloy. Once the blank is formed, grinding and lapping are no problem. High quality balls can be produced from this material.
We manufacture and stock a large variety of brass balls. The Standard alloy is 70-30, which is 70% copper and 30% zinc. 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.
Hevimet is usually sintered from powdered tungsten and powdered copper. It is machinable. Unlike lead, it is a biologically safe, very heavy material. Ball's made of this material are used as counter weights, and to add mass to mechanical structures.
Titanium Balls are made in two popular titanium materials. The first is basically pure titanium. This material is widely used in medical applications, where it is frequently used in body implants. 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 form for easy processing into precision balls. Satin finished titanium balls are used as calibration devices for optical inspection devices.
Tantalum balls or beads find frequent use as radiographic markers, because of their bio-compatablity. These balls balls or beads can be implanted to form three dimensional markers for orthopedic evaluation after surgery. A ring or these radio graphically opaque markers used at both ends of stints and shunts provide a well defined address for the implanted devices. An attached ball will define the position of a catheter. Tantalum's, ( Ta ) atomic weight is 180.947, density: 16.6g / cm^3. There is no reaction with either hydrochloric acid ( HCL ) or nitric acid ( HNO3 ).
See our sister site, www.tantalumbeads.com, for more information.
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.
| Ni, Nickel | 35% |
| Co, Cobalt | 35% |
| Cr, Chrome | 20% |
| Mo, Molybdenum | 10% |
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.
Tungsten has one of the highest melting points of any available metal. This is one of the heaviest metals. It is hard and it is tough. 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.
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.
There are a number of different Monel alloys. 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.
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.
Inconell is one the exotic space are metals. This metal has good high and low temperature qualities. It has good corrosion resistance. This metal alloy must be heat treated to develop its good physical properties. This is a very expensive material. 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.
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.
We manufacture copper balls in the entire range of sizes from subminiature to several inches in diameter. Pure copper, as well as the many copper alloys can be used to produce highly accurate precision balls.
Copper has excellent electrical and heat conductivity, as well as good corrosion resistance in many harsh environments.
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 effected. 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.
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
For more information on
engineering materials, see the site matweb.com .
Copyright © 1999-2008
Micro Surface Engr. Inc. |
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