Outstanding advantages of synthetic Sapphire Jewel Bearings:
Mounting Jewel Bearing Design Aids | Ring Jewel Bearing Design Aids | Vee Jewel Bearing Design Aids | Endstone Jewel Bearing Design Aids | Cup Jewel Bearing Design Aids | Orifice Jewel Bearing Design Aids | Pivot Jewel Design Aids
Jewel bearings are normally mounted in some type of housing. This housing may be a screw, bushing or plate fabricated from half hard brass, C.R.S., stainless, aluminum or other metals. Mounting is generally accomplished by spin setting or friction set. By this method, the jewel is forced into a hole drilled to create interference fit with the OD of the jewel.
Spin setting is the more generally used and more satisfactory mounting method because minimum pressure is applied on the jewel, and there is less danger of breakage or damage. The jewel is placed in position in the hole and setting material is spun over the edge of the jewel to hold it in place.
Spring-loaded mounts offer a factor of safety in jewel bearing assembly and jewel bearing application. With rigid mountings, excessive tightening of the jewel bearing can cause the pivot to bottom with the possibility of damage to the jewel bearing or pivot. With spring set jewels, the jewel bearing adjustment is not critical.
Ring Jewel Bearings serve as radical or sleeve jewel bearings used with a straight cylindrical shaft. They offer a great flexibility in jewel bearing design because of the many possible combinations with endstones. Rugged straight hole rings restrict lateral movement to a minimum but require accurate alignment when the clearance between pivot and the jewel bearing is closely held. An olive hole (radiused ID) jewel offers lower friction bearings with the pivot and permits adjustment in the jewel bearing assembly. A bombé face provides minimum contact with a shouldered pivot for light, intermittent end thrust. Where thrust load is continuous, an endstone is usually combined with the ring jewel.
Typical Ring Jewel Bearing Applications: General Instrumentation, Gauges, Meters, Indicators, Watches, Clocks, Potentiometers, Gyros, Aircraft Instruments.
Vee Jewel Bearings are well suited to sensitive instruments where the moving element is light. They offer minimum friction when used with conical, small radiused pivots and permit slight lateral movement. The jewel radius should be 3 times larger than the pivot radius for low friction torque, sensitivity, and resistance to deformation. The contact area of the pivot should be highly polished and a micro-inch finish of 2 or better on the pivot radius is recommended.
Typical Jewel Bearing Applications: Ohmmeters, Voltmeters, Gauges, and other Indicating Meters; Timers and Relays.
Endstones find wide use as a thrust bearing in combination with a ring jewel which serves as the annular jewel bearing. The endstone may be mounted in the same housing with the ring jewel or mounted separately in an adjusting screw—especially when the end of the pivot extends beyond the radical bearing. Pivot ends in both cases should be highly polished. Endstones are also used as spacers or insulators.
Typical Endstone Jewel Bearing Applications: General Instrumentation, Insulating Spacers, Time-keeping movements.
Cup Jewel Bearings are generally used with a semi-spherical pivot or in a jewel bearing design that fits a ball bearing between two cup jewels. They are widely used for vertical shaft applications.
Typical Cup Jewel Bearing Applications: Compasses, Heat Monitors
Orifice Jewels are a development of the vee jewel and are sometimes called drilled vees. Sapphire is an excellent orifice material because of its resistance to wear, heat and corrosion, as well as its low friction. The hole diameter for control purposes is usually specified to be held within 0.0002”. Sapphire orifices can be used for UHP water jet applications (up to 40,000-50,000 PSI), oil atomizing and the handling of air, hot gases and practically all liquids and acids.
Typical Orifice Jewel Applications: Control Units (gas, liquid), Flow-meters, Ultra-High Pressure Water Jet, Ink Jet Printing.
The shape and type of the pivot used are determined by the operating conditions, the type of jewel, and other jewel bearing design factors involved in suspending the moving element in the system. Cylindrical pivots can be supported by any of the ring jewel bearing designs and combinations. End thrust may be taken by having a shoulder on the pivot ride on the polished face of the jewel or by using an endstone with the ring jewel to take the thrust from a pivot with a rounded end. Pivots with radiused conical ends are generally used with vee jewels. Rounded or semi-spherical pivots are used with single cup jewels and flat endstones. Since working areas of the jewel bearing are lapped to a mirror finish, the contact area of the pivot should be highly polished for best performance. On pointed or ball end pivots, a finish of 2 micro inch or better on the pivot radius is recommended. Through our affiliate, HERMAN D. STEEL COMPANY, we can furnish miniature pivots of most materials turned with extreme accuracy. Especially recommended is “Nivapoint”, a patented, non-corrosive, non-magnetic material with excellent tensile strength and hardness. Please consult us on your pivot requirements.