Most Common Ball Materials

Ball Technical Data Sheet #1

Metals Used to Manufacture Balls

Metal	Manufactured from	Magnetism	Machinability	Hardness
Chrome Steel	Steel of the through hardening type AISI E-52100	Strongly attracted by magnet	Can be drilled by EDM and modified by grinding	60-67 HRC
Hardened Stainless Steel	Steel AISI type 440C	Strongly attracted by magnet	Can be drilled by EDM and modified by grinding	58-65 HRC
Unhardened Stainless Steel	Steel AISI type 316 or 302	Only slightly magnetic	May be machined, drilled and tapped	30 HRC
Brass	Copper 60-70%, Zinc 30-40%	Nearly non-magnetic	Easily machined, drilled and tapped	5-87 HRB
Soft Mild Steel	Steel AISI type 1018	Strongly attracted by magnet	Easily machined, drilled and tapped	28 HRC
Aluminum	Aluminum Assoc. Spec. No. 2017, SAE No. 26	Non-magnetic	Easily machined, drilled and tapped	54-72 HRB
Tungsten Carbide	Tungsten Carbide 93.5 - 94.5%, Cobalt 5.5-6.5%	Slightly magnetic	This material is not easily machinable, use EDM or diamond grinding	87.5 - 90.4 HRA

Chrome Alloy Steel Balls: The most common bearing alloy, are manufactured from steel of the hardening type AISI E-52100. The balls are heat treated to a hardness of 62 HRC minimum. They are strongly attracted by a magnet.
Hardened Stainless Steel Balls: Are widely used in bearings and valves, and are manufactured from steel AISI type 440C. Hardness is 58 HRC minimum. They are strongly attracted by a magnet.
Unhardened Stainless Steel Balls: Are manufactured from steel AISI Type 316 or 302. This material is only slightly magnetic. It may be machined, drilled, and tapped. It has the best corrosion resistance of the standard metals. Hardness is about 30 HRC.
Brass Balls: Are widely used in tooling and are manufactured from Copper 60-70%, Zinc 30-40%. They are easy to machine, drill, and tap. This material is nearly nonmagnetic. Hardness is 80 HRB.
Soft Mild Steel Balls: Are manufactured from steel, AISI type 1018. They are strongly attracted by a magnet. Soft mild steel is easy to machine, drill, and tap. The balls are highly polished for decorative applications etc. Hardness 28 HRC.
Aluminum Balls: Are manufactured from Aluminum Association Specification No. 2017 (SAE No.26). The material is nonmagnetic. It is easy to machine, drill, and tap.
Tungsten Carbide Balls: Are manufactured from high grade material in the range of Tungsten Carbide 93.5-94.5%, Cobalt 5.5-6.5%. The balls may be ground with diamond wheels and shaped with electro discharge machines. This is one of the hardest, toughest, and most rigid materials available. It is slightly magnetic.

Plastics Used to Manufacture Balls

Plastic	Resistant to	Physical Properties	Maximum Usable Temperature	Specific Gravity	Water Absorption
Nylon	Oils, greases, electrolytic corrosion and most organic solvents	High Tensile strength, abrasion resistant, high compression strength, low coefficient of expansion, very good electrical properties	360°F.	1.09 - 1.14	Is hygroscopic and absorbs considerable amounts of water, .4 -1.5%
PTFE	Practically all organic solvents, strong caustics, cryogenic missile fuels, liquid oxygen, and concentrated acids	Good physicals from cryogenic temperatures to over 500 °F, good compressive strength	550°F	1.13 - 2.22	zero water absorption 0% < .01 %
Polyethylene	Bases, weak acids, and organic solvents ( except chlorinated ones )	Attacked slowly by oxidizing acids	175°F	.90 - .91	low water absorption, low density, will float in water, .02%
Polypropylene	Bases, weak acids, and organic solvents about 80 °C	Attacked slowly by oxidizing acids	320°F	.90 - .91	low water absorption, low density, will float in water, .01%

Ball Technical Data Sheet #2

Nylon Balls: Are resistant to most common organic solvents, oils, greases and electrolytic corrosion. Nylon has a good heat resistance, high tensile strength, fatigue endurance, compression and shear strength, abrasion resistance, low coefficient to friction and very good electrical properties.
PTFE Balls: Are unaffected by practically all organic solvents, strong caustics, cryogenic missile fuels, liquid oxygen and concentrated acids. They have zero water absorption, while maintaining the highest heat resistance of all thermoplastics. PTFE has good physicals with cryogenic temperatures to +500 °F and good compressive strength.
Polyethylene Balls: Are resistant to organic solvents, except chlorinated ones, and to bases and weak acids. They have very low water absorption, and they will float in water.
Polypropylene Balls: Are resistant to organic solvents below about 80 °C, to bases and weak acids. They are only slowly attacked by oxidizing acids. They will float in water and have a low water absorption.