Category: Products > Extrusions For Heater Industry


Tubular cores, Spiral heater cores, Alien cores, oval cores, Swageable Cores, Swageable Insulators

INTRO: MgO cores of this type are intended for applications which might involve much bending and reshaping of the heater to make complex shapes. The “coil” is typically made by building a straight heating element and spirally winding the element onto a mandrel to make a finished heater. Identical insulators may be used for cable and tubular applications as well. It is helpful to distinguish the end use in order to optimize the ceramic properties for the complex manufacturing steps.

MgO cores of this type are characterized by the need for generally small dimensions and ability to compact efficiently without losing the ability for re-shaping of the finished cable.  The heater is inserted inside the insulator which may be a tubular geometry, or a multi-hole geometry with similar or dissimilar sized bores.

Insulator designs may have distinguishing characteristics such as:

1)  tubular designs of 2.5 mm OD or less
2)  4-hole designs of 2.5-4.5 mm OD
3)  Oval cross sections in 2 or 4 hole designs up to about 5 mm OD
4)  4-hole designs with 2 different hole sizes aligned adjacent instead of opposed (described by TATEHO OZARK as “alien” configuration)

Insulator for this application require a proper combination of dimensional, material, physical, electrical, and microstructural properties.  They are extruded into the final shape with no machining of dimensions except for length.  The MgO grade is a high performance heater grade with optimum dielectric and insulation resistance properties.  The grain structure must provide proper firing results for strength and dimensions, and proper compression reaction upon swaging.


It is not necessary to stipulate an TATEHO OZARK grade.  TATEHO OZARK uses high quality electrical grade fused MgO from two North American sources.  The minimum MgO content is 96.4% MgO with appropriate limits for impurities and magnetic iron.

For the purpose of finished part identification, TATEHO OZARK part naming will use the prefix “T”.

Your certification paperwork may indicate one of the above designations, which are used internally to specify and engineer the perfect MgO grind and blend for your part.

The following are typical analyses or limits for powders used to produce MgO wind cores. All raw materials are high quality fused grain powders which are processed in-house to obtain optimum particle size distributions for end use.

MgO (%)97.44
Al2O3 (%)0.36
SiO2 (%)1.41
Fe2O3 (%)0.06
CaO (%)0.73
B (PPM)<30
Cd (PPM)<30
S (PPM)<10
C (PPM)<10

As very fine scale parts, it is important to provide strength and hardness compatible with production experience by the user.  OZARK will suggest optimium values for hardness or firing temperature to assure smooth continuity from shipment to shipment.

Insulators are fired to uniform mechanical strengths which have been established for optimum handling and swaging characteristics for different applications. A true mechanical test does not exist to characterize “crushability”. A Modulus of Rupture measurement is normally provided for historical tracking purposes.  This test is a modified three point bending test performed according to ASTM standard E1652 Appendix 4 and has many limitations.  Please refer to our Technical Bulletin.